Model

New Tools
PolyBridge - The PolyBridge node builds sheets or columns connecting edges or faces. The node has controls for the shape and topology of the bridge, including following a curve.
PolyExtrude - New PolyExtrude extrudes sheets or columns from selected edges or faces. The node has controls for the shape and topology of the extrusion, including following a curve.
PolyExpand2D - New PolyExpand2D node dilates or expands the outlines of polygons. It can also create width from lines, making it ideal from creating roads from path lines.
Bend - The new Bend node is a more interactive version of Twist. It lets you define two planes and twist, bend, or taper any geometry between them.
Topo Build - This tool lets you interactively builds a quad mesh over existing template geometry. Points automatically snap to the surface of the template geometry to create a 3D tracing of its topology.
Editing Components
Multi-selection - The Edit node has a free-flowing multi-selection“tweak”-like tool. You can select faces, edges, or points on-the-fly instead of switching between different components.
Tweak Edit - When tweaking points, edges and faces, the handle will remain hidden to let the modeller focus on the geometry.
Edge Sliding - You can slide edges and edge loops across the surface. You can constrain points and faces to slide across adjacent faces.
Selection Highlighting - The geometry under the mouse highlights in the viewport to show what will be selected.
Soft Transform Visualizer - The Soft Transform and Soft Peak nodes now let you visualize the falloff using a visualizer.
Repeat Edit - When you're working in the Edit, UV Edit, or brush tools, the Q (Repeat current operation) and ⇧ Shift + Q (Branch and repeat current operation) hotkeys will now create a new node instance.
Group List
Select Branches - You can now select whole branches of attribute hierarchies in the group list interface, for example with an Alembic path attribute.
Highlight Names - There is now an option in the group list’s settings menu to highlight group names in the list as you move the mouse over components, instead of changing the contents of the list to only show the groups containing the component under the mouse.
Default Colors - Changed default group list colors to prevent confusion with the selection.
Customize Colors - You can now customize the colors assign to groups in the group list.
Collapse and Expand - You can now collapse and expand branches of Alembic hierarchies in the group list.
Looping
For- Each Loop - Block Begin and Block End nodes allow looping the nodes between them. This block functionality is easier to use than previous solutions such as the For Each subnet and Solver SOP.
Group Syntax
Selection Syntax - The group selection syntax now supports using @attr=val,val,val to compare an attribute to a list of possible values. For example, @id=1,2,90,120. For string attributes, you must enclose values containing spaces in double quotes, for example @path=/foo/*,/bar,"some string".
Wranglers
Generate Parameters - The wrangler nodes now have a button next to the VEX snippet to generate parameters from any ch() references in the code.
Modify Point Positions - The Deformation Wrangle node lets you write VEX code to modify point positions, and then takes care of the details of transforming other attributes and updating packed primitive intrinsics.
Run over > Numbers mode - The Attribute VOP SOP, Attribute Wrangle SOP, Geometry VOP DOP, and Geometry Wrangle DOP have a new Run over > Numbers mode, which runs the VEX code a certain number of times.
Enhancements
Volumes - Points from Volume has a new Construction method parameter. The default for new nodes is “Sparse volume” which is more efficient for sparse inputs than the original method, which is now available as “Dense grid”. The Fluid Source and Grain Source nodes have this new parameter as well. When the method is “Sparse volume,” the node also has new parameters for only creating points within a certain slice of the volume.
Voronoi Fracture - The Voronoi Fracture node now has a separate option to compute vertex normals on the surface (exterior) geometry. When this is on and the input doesn’t have normals, the cusp angle for the interior normals won’t be used for the exterior.
Shortest Path - Find shortest path has a new parameter to create a point attribute indicating the previous point number in the path. This is easier to traverse in VEX than output polygons.
Shrink Wrap 2.0 - New Shrink Wrap version 2.0, using the convex hull algorithm from the Bullet solver. This is significantly faster and produces simpler geometry over convex hulls.
Attribute Handling - Attribute Swap node swaps, moves, or copies attributes efficiently with support for pattern matching.
UVs
UV Flatten - The UV Flatten node has a new option to use existing UVs. This lets you use the node’s pin and cutting tools on existing UVs.
UV Layout - The UV Layout node has a new parameter to “correct” the size of UV islands based on their 3D areas.
Soft Transform Visualization - Added visualization of the soft radius falloff to the UV transform and UV Edit geometry nodes. The nodes now create an attribute you can see with a visualizer.
UV Boundaries - Added visualization of UV boundaries in the viewport.
UV Quickshade - The UV Quickshade node’s default texture is now a high-res checkerboard. This is also the background for UV viewports.
Subdivision Curves
Subdivision Curves - Support for subdivision curves in Mantra, the viewport, and the Subdivide and Resample nodes. This displays/renders polylines as subdivided curves.
Fur Object Display - This lets you store low-res polylines but display and render them as high-res curves. The Fur object now uses subdivision curves instead of NURBS for big performance gains.
Display Options - The Display as > Subdivision surface option on objects is now “Subdivision surface/curves”. When this option is on, polylines in the object will display/render as subdivided curves.
Alembic And Packed Geometry
Alembic I/O - user properties on Alembic hierarchies now import and export as custom parameters on nodes or attributes on packed primitives.
Geometry Loading - The Alembic geometry node can now specify the geometry types to load. You can also now load only transforming or only deforming geometry. A new option on the Alembic Archive object lets you load the entire hierarchy in a single Geometry object. If the Alembic file contains cameras, they will still be loaded as separate objects.
Object Exclude - The node now has an Object exclude parameter which can hide some objects in the Object path. Both Object path and Object exclude have buttons that let you choose objects either from a tree or from the viewport.
Group Naming Mode - The node has a new group naming mode which uses the shape’s base name (without the full path).
Export - Alembic export now adds an X.samples property on the archive to match Maya’s custom tag. This lets you query how many samples are stored in the archive.
Bounds - When you save an Alembic archive with “full bounds”, the child bounds for the entire archive are stored on the root node. This lets you query the entire archive’s bounds.
Alembic Render - The Alembic render node now uses indexed samples when writing UV attributes.
Packed Primitives
Pack Node - The Pack node can now transfer attributes to the detail containing the packed primitives.
Pack Points and Unpack Points - New Pack Points and Unpack Points nodes allow efficient use of only the points in a specific spatial region. This supports on-demand loading of very large particle sets, for example much faster flipbooking of FLIP simulations with many millions of points.
Apply StyleSheet - New parameters on the Unpack node let you optionally apply and attach a stylesheet to the unpacked primitives.
gPlay - You can now unpack geometry inside the gplay utility. This lets you view attributes on the unpacked geometry.
Other Changes And Improvements
Geometry spreadsheet - Group membership now appears as a special group:name column in the geometry spreadsheet, where each row has 1 if the point/primitive is in the group, or 0 if it’s not. You can hide or show the groups using patterns in the Attributes filter field. For example, ^group:* to hide all group columns, or * group:door to show all regular attributes and also the door group.
VDB - The Convert VDB geometry node now has an Activate inside voxels parameter. You can turn this off when converting an SDF with Signed flood fill to only activate the voxels containing the SDF shell.
FBX - Added options to the fbximport HScript command. When importing FBX that uses Softimage hierarchical scaling for transforms, we now resample at playback sample boundaries to avoid interpolation errors.
Interface - Improvements to the Reselect button next to Group fields. Handle improvements, including a new orient handle type.

Render

Shader Building
Shader FX 2.0 - The shader FX menu has been reworked to provide access to a wider selection of VOP nodes.
New High-level shader VOPs supporting layering:
Principled shader VOP - implements Disney’s physically-based Principled Shader which is designed to provide artistic flexibility with a minimal set of controls. You can learn more from Disney’s Technical paper [PDF].
Surface Model VOP 3.0 - uses more physically correct model and parameter defaults.
Glass shader VOP - with attenuation and fake caustics.
Skin shader VOP
Brushed Metal shader VOP - A new supporting Brushed Circles VOP makes it easy to calculate tangents for a circular brushed metal look.
Material Gallery - New gallery of useful materials wrapping the new VOPs, including Principled and Mantra Surface “uber-shaders”.
Car paint material
Metal materials based on physical properties of different metals.
Fake Caustics shader VOP.
New Pyro shader nodes with much simpler interfaces.
Lava material for new viscous fluids tools. Includes dual rest support.
PBR-ready Textures - A collection of high-resolution textures, saved as .rat files for use in Houdini will be available on the sidefx.com website under Downloads > Textures. These are PBR ready and royalty free. In addition to .rat files, .tiff files are available for use in photo editing packages such as Adobe PhotoShop.
Dirt Masking - Dirt Mask VOP uses an algorithm similar to ambient occlusion to mask crevices or geometry edges. This is useful for layer blending.
BSDF Tint VOP - Tints a BSDF with separate control over colorization and luminance.
Conductor Fresnel VOP - Conductor Fresnel VOP computes a reflection blending factor based on reflectivity and edge tint (or eta and kappa).
Material SOP - The Material SOP can now reference shader VOPs in addition to SHOPs.
Tab menu - Reorganized the VOP network Tab menu.
Layered Shaders
Layered Shaders - Layering of shaders at the VOP level.
New VOPs for layering - Layer Pack, Layer Unpack, Layer Mix. Compute Lighting now has outputs for layer components.
Detail Maps
Viewport support - Houdini has viewport, rendering, and shading support for generating and using normal maps to add detail to low-poly models at display/render time.
Displace VOP - Displace VOP supports bump, normal, displace along normal, and vector displacement (in object and UV tangent space).
Displacement Texture VOP - Displacement texture VOP builds on Displace with built-in texture sampling. The Tab menu has aliases for the various modes - Bump Texture, Normal Texture, Displacement Texture, and Vector Displacement Texture.
Tangent Space Normal Maps - The Tangent Normals and Tangent Normal Remap VOPs let you import and export tangent space normal maps.
Tangent Normals - The Mantra materials now export an Nt tangent normal image plane. The tangent normals are affected by displacement, normal maps, and bump maps.
Convert to Normal Map - Bump to Normal Map VOP converts bump maps to normal maps.
Material Gallery
Mantra Surface shader
Now a Precompiled Digital Asset, for much faster loading and render startup for scenes with many shader instances.
Supports tangent space vector displacement and tangent space normal maps.
Separate bump/normal controls for coat reflections.
Cleaner implementation makes it easier to modify.
Computes tangents using the uv attribute, or geometric tangents if the surface has no UVs. This gives usable tangents on NURBS and geometric primitives.
Decomposed the Mantra Surface functionality into smaller re-usable pieces: Compute Lighting (new version with layer input), Physically Based Diffuse, Physically Based Specular, SSS Component, Attenuate.
New Surface Model VOP version 3.0 is being used which adds layer output, uses Fresnel blending by default and intensities are now set to 1.0 by default. Diffuse color is 0.2 grey so it reads as 50% grey after 2.2 gamma correction. Tangent style is now “Compute from UV”.
Replaces N input with baseN and coatN to support clear coat.
Metallic and edge tint controls.
Removes unused inputs.
Fades out reduction of diffuse intensity at grazing angles when specular intensity is reduced. This means overall energy should stay constant when you reduce specular intensity. This is not based on physical laws, but fixes dark edges that would otherwise appear around objects.
Principled shader - Principled Shader wraps the the Principled Shader VOP and adds texture inputs for all main parameters.
Liquid shader - Rewritten Basic Liquid shader.
Controls for boosting diffuse intensity in high-vorticity areas.
“Vorticity waves”: extra bump-mapped wave detail added in high-vorticity areas, driven by FLIP Fluid’s dual-rest attributes.
Toon shader - New Toon Color Shader and Toon Outline Shader create stylized cartoon looks.<
Other Materials:
Car paint material.
Metal materials based on physical properties of different metals.
Fake Caustics shader VOP.
New Pyro shader nodes with much simpler interfaces.
Lava material for new viscous fluids tools. Includes dual rest support.
Gallery Folders - You can now use slashes in material gallery entries to put the entry inside a folder (for example, Metals/Gold, Metals/Steel) in the material list.
Reorganized - The material gallery has been reorganized using new materials, removed obsolete materials. Some materials are now precompiled digital assets.
Drag and Drop - You can now drag and drop material assets from the gallery to assign them, not just SHOPs.
Material Stylesheets
New Interface - Material stylesheets let you select and apply materials to any geometry (including packed geometry and instances) at render time. The foundation existed in Houdini 14, but Houdini 15 adds refinements and includes a tree editing pane making it easier to create and edit stylesheets.
Subdivision support - Material stylesheets can now enable/disable subdivision rendering.
Material SOP - The Material geometry node has a parameter to add a stylesheet attribute to the geometry.
Pyro Shading
Pyro Material 3.0:
Streamlined interface, removed rarely used functionality.
Commonly used parameters are all on one tab.
Improved interactivity (parameter changes no longer cause recompilation).
Default Pyro smoke is now half as bright to match other volume shaders.
New Pyro Shader Core VOP replaces Pyro Shade VOP.
Layer output.
Uses common input/output names.
No scripted parameter promotion magic.
Removes draw input. If you need masking, you need to do it externally.
Parameter changes don’t trigger recompilation.
Only supports the new density and brightness models. Removes model choice and fireexist.
Smoke brightness now matches other volume shaders.
No longer computes Cf internally, since this is not compatible with layering. Instead the Compute Lighting VOP takes care of this. This means the node doesn’t support turning off shadow computation.
New Unified Noise VOP:
Simplified implementation, removed parameter promotion magic.
Parameters have corresponding inputs.
Parameter changes don’t trigger code-generation (except signature parameter). This means that it can now be used in Precompiled HDAs.
Built using new VOP nodes:
New versions of many Pyro-related VOPs remove scripted parameter-promotion magic.
A new version of the Ramp Filter VOP now accepts a Ramp struct instead of individual arrays.
A new version of the Dual Rest Solver VOP has a DualRest struct output, which you can wire directly into the updated Unified Noise VOP.
Instead of multiple dual rest inputs, a single input that accepts a DualRest or DualRest4 struct input, as produced by the updated Dual Rest Solver VOP.
Lighting
Physically correct - The default lights now use “physically correct” attenuation, meaning the light drops off exponentially with distance.
Light Exposure - A new Light exposure parameter on lights lets you exponentially scale brightness (value = intensity × 2exposure).
Auto-Intensity - When you create a physically correct light by Ctrl-clicking a light tool on the shelf (which positions the light based on the current view), the tool automatically adjusts the intensity of the light so that the brightness of the light at the viewport pivot will be 1.
IES Scattering Profiles - Houdini now includes IES light scattering profiles from derekjenson.com. You can find them in $HFS/houdini/ies. You can apply them to a spotlight using the Environment/IES Map parameter on the Spotlight options tab.
New Defaults - The Mantra Surface shader and Surface Model VOP use more physically plausible defaults.
Tube light - You can now create a “tube” Area light. The Size parameters control the length of the tube and the radius.
Distant Light - Looking through a distant light displays an orthographic view.
Tag Visualizer - Track lights and cameras both on and off the screen.
Mantra Rendering
IPR Feedback - The render view now shows elapsed and final render times, peak memory usage, and estimated time remaining. This information is saved in image files that support arbitrary metadata such as Pic, Rat, and OpenEXR. MPlay will display the metadata when you load files that contain it.
Quality controls - The Mantra render node now has controls to scale the Max samples setting separately for the diffuse, reflection, and refraction components. Increasing the scale decreases the acceptable noise level when rendering that component. This lets you have Mantra devote more effort to components that have high variance.
Adaptive BSDF - BSDF sampling super-samples the BSDF in areas where radiance is changing quickly. This generates images faster with better distributed noise in PBR mode. For now this is not available in the default render node parameters. To add it, use the Edit Rendering Parameters interface.
Checkpointing - By default Mantra now writes out “checkpoint” files containing the current render state at certain intervals. If the render fails because of a fixable problem such as out-of-memory, you can resume the render from the last checkpoint by turning on Resume from checkpoint files on the render node.
Checkpointing - Checkpointing is available for Mantra’s native image formats (.pic and .rat) as well as .exr. If the checkpoint files are taking up too much disk space, you can turn them off on the render node. HQueue has a new Mantra options > Enable checkpoints setting. When this is on (the default), HQueue will resume rescheduled jobs using checkpoints.
IFD Compression - New File compression parameter on the Driver tab of the Mantra render node to control compression of IFD output.
Velocity Blur - New “Automatic velocity blur” setting for Allow motion blur only enables blur if a velocity attribute exists in the scene.
Z-back - Houdini now supports both “Z front” and “Z back” in deep images. By default, Houdini will only add zfront and zback for deep camera images, unless the planes are listed in the Depth planes parameter. When rendering .rat texture images, Mantra will store zfront/zback as Pz and dPdz (delta Z) planes. When rendering .exr images, Mantra will store them as Z and Zback. The dcmconvert command line utility knows to map between the different names.
RenderMan 20
RenderMan 20 Support - Houdini supports RenderMan 20.0 and RIS shading. RIS shaders are available in the RIS Shader Network SHOP.
Native environment for building RIS shaders in VOPs (with OSL support)
Library of BxDF RIS VOP shaders
Updated ROP and SOHO bindings
Added RIS shader nodes:
Complete set of RenderMan BxDF, Pattern, and Integrator RIS shaders.
PxrStdAreaLight, PxrStdEnvDayLight, and PxrStdEnvMapLight RIS light shaders.
Camera, Light Probe, and Rolling Shutter RIS projection shaders. You can add projection shaders to a camera using the Lens Shader property.
New RIS render node - This allows the RIB and RIS render nodes to have cleaner interfaces specific to each mode.
Older Version Support Removed - Removed support for RenderMan versions before 17.
Compositing
PSD import - Houdini can now import Photoshop (PSD and PSB) files into a compositing network, preserving layers. Use File > Import > Image to choose a file to import.
Drop shadow - Added Drop Shadow compositing node to simplify creating shadowed text layers.
HQueue
Job ID Display - You can configure Houdini’s HQueue Render and HQueue Simulation nodes to display the job ID when you submit a new job to HQueue.
Diagnostic Information - You can now download diagnostic information from HQueue’s details page to send to Side Effects software support.
Browser Management - You can now add and remove clients to/from a job in the browser, and through the HQueue Python API using getPermittedClientList and savePermittedClientList.
Client Disabling - Changed how client disabling works. You now specify in hqserver.ini the maximum number of failures allowed on a client under a single root job. Clients with more than this number of failures will not be assigned new jobs.
PBR Texture Baking
Bake UVs - Rendering UV texture maps is now handled by a separate Bake Texture render node. UV texture rendering functionality has been removed from the Mantra render node. UV rendering with micropolygons is deprecated in favor of raytraced UV rendering.
Utilities
hrender - Added an option to hrender to specify the take to render. hrender is more responsive.
vexexec - The vexexec utility now has a -V verbose option.
MPlay - MPlay will now load images from an http: URL on the command line.
Miscellaneous
Particle radius - Mantra now renders particles using the object’s Point Scale and Treat point scale as diameter instead of radius parameters (on the Render > Geometry sub-tab). This may change the scale of particles when rendering old scenes. The quick fix it to turn on Treat point scale as diameter instead of radius.
Mantra verbosity - New verbose flags: -t/T – turn on/off time stamps on log messages (on by default), -a/A – Turn on/off Alfred-style progress updates. For example, mantra -VaT3 will render at verbosity level 3, with Alfred-style progress reports, but no time stamps on log messages.
Console Output - Mantra’s console output is now timestamped and errors/warnings are color-coded. You can turn off coloring in the parameters of the Mantra render node.
Motion Segments - Added limited support for motion segments on arbitrary attributes. They are not shaded, but you can query the segment values. The geometry:segmentattrs property specifies which attributes should create motion segments (automatically includes P).
Image Planes - You can now disable specific image planes in filter scripts using a disable property.
OpenEXR - You can add the vm_open now automatically sets the “data window” on OpenEXR images after rendering, equivalent to running the iautocrop utility. You can turn this off if necessary.

Animate

Workflow
Onion-skinning - Per-object onion-skinning in the viewport. Use the Onion skinning menu on the Misc tab of the geometry object to choose between “Transform only” and “Deforming” onion skinning. You can set the number of before and after frames and other settings in the scene view’s display options.
Orient by object - Objects now have a Look up parameter. This is like the Look at parameter, but it sets the object’s up vector to point at another object. This makes it easy to animate path following and orientation without expressions.
Keep position changed - Instead of a global Keep position when moving parent checkbox in the preferences, there is now a default Child compensation preference, and per-object settings on each object’s Transform tab. When “Child compensation” is on, moving an object does not change the position of its children - their transforms are edited to compensate for the change. For convenience, Keep position when parenting and Child compensation are available as options in the toolbar of the Move tool.
Tuple Parameters - Auto-key tuples parameters (on by default): enables Auto-key for tuple parameters. This is important when animating with the handles.
Scoping - Scope parameters with animation (on by default): the animation editor will scope any parameters that have animation, so you don’t have to set auto-scope on parameters or manually scope them.
Deformation Wrangle - Runs a VEX snippet to deform geometry.
Animation Editor
Dope Sheet Ripple - The new Ripple tool lets you easily shift groups of keys in the dopesheet.
Box Select - You can now box-select multiple keys and transform or stretch them in the dopesheet and timeline.
Automatic Slope - The = hotkey now sets the selected keyframes to automatic slope. The - hotkey sets the selected keyframes to manual slope. This is easier to use than the previous behavior where = toggled between the two modes.
Normalized Acceleration - Smooth Selected and Auto-Slope now normalize the acceleration. If you want to change acceleration, you must set the keys to have manual slope.
Undo/Redo - Dope sheet selections now support undo/redo.
Channel Extend - You can cycle animation outside the keyframe range (default, hold, extend, cycle, slope, cycle offset, or oscillate). In the graph editor, choose Channels > Edit channel properties.
Bake Cycles - You can also bake out cycles into real keyframe animation.
Character Animation
Simple Biped Rigs - Textured female and male versions of the simple biped rig. All of the rigs include character picker and pose library options. The Simple Biped rigs have onion skinning, render as subdivision, and squash and stretch controls.
Dual Quaternions - Dual quaternion skinning is an alternate way of computing the deformation from bones. This method is better for deforming twisting geometry and preventing volume loss than the traditional Linear Skinning method. This is often used for body parts, such as the shoulders of characters.
Blend Dual Quaternions - Blends the deformation computed using both methods together based on a point attribute.
Match Transformations - This button will let you grab TRSP parameters from another object and apply them to your current object while taking into account any existing hierarchies.
Character Picker Pane - New character picker is implemented as a dedicated Python panel and can be used to select parts of a character even if the character’s null controls are hidden.
Pose Library Pane - Save and load poses and clips for characters using the new pose library pane. Implemented as a Python panel, this pane can load saved poses from characters such as the simple rigs.
Capture geometry - The Capture Attribute Pack and Capture Attribute Unpack geometry nodes convert between traditional “index pair” storage of capture attributes, and a group of named array attributes. The array representation is easy to bind and manipulate in VEX, but does not support interpolation.
Easier bone selection - You can now select wireframe (X-ray) bones by clicking inside the bone as if they were solid.
Other Changes And Improvements
Pre-transforms - You can add a pre-transform parameters to an object’s interface. In the parameter editor, click the gear menu and choose Edit parameter interface, then drag over the Pre-transform folder from the Node properties tab.
Bake keyframes - You can now bake keyframes from the parameter context menu.
Scripting - The Python Script object lets you generate an object transform from a Python script. The node includes examples in the presets menu for the script field. The new hou.Parm.setKeyframes method is more efficient than calling hou.Parm.setKeyframe multiple times.
Shelf Tools
Agent Cam tool creates a camera and attaches it to the head of an agent for point of view shots.
Target Position tool makes agents move toward a target.
Shading And Rendering
Material stylesheets allow you to change materials and material parameters per-agent.
New VEX functions agentlocaltransform, agentworldtransform, setagentlocaltransform, setagentworldtransform for reading and writing specific agent transforms. These are much faster than functions such as agentlocaltransforms that work on all an agent’s transforms.
Agent Add Clip VOP is a wrapper for the agentaddclip VEX function.

Crowds

Ragdoll Dynamics
You can now switch agents to a rag doll state.
The Collision Layer and Configure Joints tools on the Crowds shelf tab let you set up collision geometry and joint rotation limits for rag dolling.
The Bullet solver solves the ragdolls.
You can use standard DOPs techniques to alter constraints, for example to have agents drop objects or detach limbs.
Ragdolls interact with other simulation types such as FLIP fluids, POP grains.
Behavior
Fuzzy Logic - Houdini now has DOP and VOP nodes to allow creating fuzzy logic “brains” to drive agent behavior.
Subsumption Logic - Support for subsumption logic allows better collision avoidance and more natural turning.
Terrain Adaptation - Terrain adaptation now supports an arbitrary number of lower limbs.
Shape Layers
New Keep external references parameter in the Agent and Crowd Source geometry nodes lets you choose whether to reference agent definition files on disk. Turning this off allows self-contained (but larger) geometry files when you export agent primitives to disk.
The Agent ROP can now write out agent definition files for an existing agent primitive.
Added support for orientation when converting agent clips to in-place animation in the Agent render node.
Agent Layer geometry node can now add deforming shapes to the layer.
Added parameters for pre-render and post-render scripts to the Agent render node.

Hair/Fur

Grooming
Improvements to Curve Groom node:
New lifting behavior and controls. Lifting with strengths from 0 to 1 should be much more natural now.
New Lock roots option. Turning this off allows hairs to move along the surface.
New Constrain length option. Turning this off allows hairs to grow or shrink.
Hair advection is faster.
Transferring Grooms - New Method menu for transferring a groom to another skin geometry, on the Skin tab of the Fur object
Performance - Improved internals and use of subdivision curves give much faster user interaction and better artistic control.
Subdivision Curves
Subdivision Curves - Added subdivision curves as an option on the Fur object. This uses polylines for the hairs, and subdivides them at display/render time. This gives substantial speed-ups over NURBS.
Viewport Display - Improved display of fur/hair in the viewport. Hair thickness, subdivision curves, and hair shadows display properly in the viewport’s high quality display mode.
Hair Material
Updated hair shader VOP and hair material in the material gallery.
New layout similar to the new Mantra Surface.
Exposed reflection size and shift parameters from the Hair Model VOP.
Removed the overall color ramp. Color is now controlled by the root and tip color, each with an optional texture map, and ramp to blend between them. A new Separate tip color parameter controls whether the tip color is different from the root.
Optional randomization of diffuse HSV and specular intensity values per-hair.

VFX

Viscous Fluids
Viscous Fluid Tools - New tools for setting up temperature and variable viscosity simulations. These tools let you create simulated lava, cooling, and melting objects.
Lava Tool - The lava tools put blackbody point colors on the fluids to create realistic molten looks. There is also a new lava shader with dual rest controls for better tracking of crust formation.
OpenCL - OpenCL support for viscous fluid simulations.
Support for viscous fluids and lava in DOPs:
Heat initialization on FLIP Object.
Gas Temperature Update DOP.
Target method on POP Attribute from Volume DOP.
Bullet Solver
Activation - The Bullet solver can now activate static objects at the instant of collision, instead of at the end of the frame. This gives a much more accurate collision response.
Friction and Bounce - You can now animate friction and bounce over the course of a simulation.
Constraints - The Bullet solver now supports disabling collisions between constrained objects. All constraint types that work with the Bullet solver (pin, spring, cone, twist, slider) now have a Disable Collisions parameter. Constraint networks can use a disablecollisions primitive attribute to disable collisions on individual constraints.
Constraint Overrides - You can now override the number of constraint solver iterations per-constraint. All constraint types that work with the Bullet solver (pin, spring, cone, twist, slider) now have a Constraint iterations parameter. Constraint networks can use a numiterations primitive attribute to set iterations on individual ties.
Angular Motors - Added parameters to the Hard Constraint Relationship and RBD Pin Constraint to allow angular motors. Angular motors specify a target relative angular velocity for the objects, which the constraint will attempt to enforce. The Angular Motor Denting example file demonstrates one use for this.
Sprint Constraints - Spring constraints are much more stable.
Solver settings - A new parameter on the solver lets you randomize the constraint solving order. This may improve stability in some situations, for a slight reduction in speed.
Custom Settings - You can use point attributes on packed primitives referenced by RBD Packed Objects to customize bullet solver settings per-object.
Attributes - The Bullet solver now recognizes the dead point attribute on packed primitives, so you can use the POP Kill DOP to remove objects from the simulation.
Bullet Ignore - If a packed primitive has a bullet_ignore attribute with a non-zero value, the Bullet solver will ignore it.
Performance:
The Bullet solver is now much faster at collisions with large numbers of closely packed static objects (such as particles).
The Bullet solver is now faster for simulations with a large number of animated static object. The interpolation of animated static object transforms is now multithreaded.
Improved Bullet solver performance when only a small percentage of simulation objects have constraints.
Collisions between compound shapes (for example glued chunks) are significantly faster. A test with four glued objects of about 20K pieces colliding against each other is around 4.5x faster than Houdini 14.
Improved the performance of constructing convex hull shapes to be about 2x faster.
Ragdoll Shelf tool - The Ragdoll tool sets up ragdoll simulations outside the crowd system.
FLIP Fluids And Whitewater
Compression - The Whitewater Source and Fluid Source geometry nodes can now cull and distribute emission based on a camera. Whitewater Source can now use particles created by the Pack Points geometry node, so it only has to unpack points in the active region.
Fluid Compress - The new Fluid Compress geometry node performs lossy compression of the output of FLIP simulations, often dramatically decreasing the disk space used by saved simulation data. The Particle Fluid Surface and Whitewater Source nodes recognize the compressed data and fill in missing particles using the surface and vel volumes.
Solvers - The FLIP Solver has new options to create decaying vorticity and dual rest attributes for use in rendering. The liquid shader now uses this feature.
Performance - Distributed global pressure solve for FLIP fluids gives greatly increased performance. FLIP fluid simulations can now handle over 2,000,000,000 particles.
Velocity Transfer - The FLIP solver has a new Velocity Transfer parameter that allows choosing between the default “Splashy Kernel” for high energy, splashy simulations, and a new “Swirly Kernel” for high vorticity simulations with less surface noise. The swirly kernel can be especially useful at small physical scale or high viscosity.
Seamless Distributed Simulations - The Distributed solve parameter on the solver turns on global pressure solving. This prevents wave artifacts along the seams between distributed slices when you're simulating a contained fluid.
Whitewater solver - The Whitewater solver now defaults to operating directly on volume data from SOPs, instead of copying them to DOP volumes, to save time and memory.
Volumetric Foam - Volumetric Foam is now on by default.
Angular Momentum - The Gas Particle to Field and Gas Field to Particle DOPs have new options to Preserve Angular Momentum with additional particle attributes when transferring velocity between particles and grids.
Particles Per Voxel - On FLIP solvers created by the shelf tools, the Particle motion > Reseeding > Particles per voxel parameter now uses a channel reference to compute a value relative to the object’s grid scale.
Surfacing - Particle Fluid Surface geometry node 2.0 includes new controls for filtering the surface, optionally based on velocity, vorticity, proximity to collisions, and other criteria. This gives much better smoothing of the fluid surface without loss of important detail. It can also copy attributes from the particles to the surface, such as vorticity and rest.
Shelf tools - Shelf tools that create FLIP simulation networks now add compression and the new fluid surfacer.
Slicing - Fixed a problem where the first cook only saw one slice if the slicing node came after the solver in the network.
Particles And Grains
Sleep/Awaken - The particle solver has an option to “auto-sleep” particles by turning on their “stopped” flag. The POP Awaken node lets you turn off the stopped flag when a key object or fast-moving particles are near. This lets you create efficient simulations where settled particles/grains don’t solve unless there’s something happening nearby. New tools on the Grains shelf tab let you set up awaken relationships in the viewport.
Sandbox Tool - New Sandbox tool for setting up common types of grain simulation.
Distributed Sims - You can now distribute grains simulations. The slice and distribution tools are now on the Grains shelf tab.
A Billion Particles - The Gas Net Slice Balance DOP can now handle more than 2 billion particles, and is better at computing time estimates.
Optimize - If you know all grains in a simulation will have the same radius, you can turn on Assume uniform radius in the solver to optimize lookups.
Activation - Simulations created by the shelf tools have activation turned off for the first frame. This lets you set up positions/constraints/etc. without constant recooks. Performance - 5x faster grains simulation for smaller datasets. OpenCL - The OpenCL version of the solver now supports varying sized grains and the attraction weight and friction attributes. Mass-shock changes - The POP Grains node’s Enable mass-shock scaling parameter is now a menu with a new “Local” option which is the default for new nodes. This computes the mass-shock “just in time”, avoiding the need for an explicit origin, and possibly running faster than looking up the mass value in memory. The node now starts with maximum acceleration turned on and set to 50 (5x gravity). Experience shows this is effective at dampening explosions caused by suddenly overlapping objects. The solver now only uses the shockmass attribute for particle interaction, not for explicit constraints or shape matching.
Sourcing - The Grain Source geometry node has an option to adjust grain sizes to avoid overlaps in the initial distribution. This avoid explosions on the first frame.
Dither - The Points from Volume and Grains Source geometry nodes have a new option to dither the surface. The Sand Box shelf tool now dithers the surface of the sand.
Particle Order - The Grain Source geometry node no longer randomizes particle orders.
Solids/FEM/Cloth
Performance - FEM simulations now run up to 10x faster compared to Houdini 14. Faster viewport display with large numbers of tets or polygons.
Self-collision - The Solid Object and Cloth Object nodes have new controls for self-collision behaviors. You can turn off collision within connected components, and collisions within fractured parts.
Embedding - The Solid Object shelf tool now sets up an embedded setup with separate geometry for simulation and rendering. This tool now uses the new Solid Embed geometry node instead of creating a chain of geometry nodes. This node embeds an input mesh into a slightly larger mesh suitable for direct simulation in the finite element solver. You can use the Element size parameter to change detail of the embedded mesh. The Solid Object and Cloth Object nodes now have a checkbox to easily enable/disable embedding.
Sourcing - The Solidify geometry node, which is useful to prepare models for tetrahedralization, now handles difficult topologies more robustly, and produces better optimized polygons.
Pyro FX
Distributed Sims - You can now distribute resizing pyro simulations.
Gas Micronodes - Gas Attribute Swap microsolver efficiently swaps around geometry attributes. This is useful for stashing and restoring attribute values.
Inputs - Gas Field VOP DOP and Gas Field Wrangle now have the ability to bind geometry, DOP data, and contexts as extra inputs. The node computes the inputs prior to running the VOPs/VEX.
Gas Curve Force - Gas Curve Force now uses force scale parameter, and shows trail guide length option.
Impact Analysis - The Impact Analysis node now has a checkbox to visualize the impact points in the viewport.
Initial State - The solid object’s Initial state tab now has linear and angular velocities like other object types.
Miscellaneous
Easy geometry visualization - Visualize Geometry DOP helps visualize geometry data in different nodes in the network. Any visualizations you attach to this node will be applied to the Geometry data in the node it’s wired from. You can hover over a DOP node and press X to rewire a visualize node onto that node. This can be very useful with the volume visualizer to inspect clouds, pyro fields, and so on.
Static/deforming objects - The SOP Geometry node has a new Transform time parameter to fetch the transform from a different time than the geometry. This allows the Static Object node to have to have proper collision velocities when Use deforming geometry and Use object transform are both on.
Object Transform - Added a parameter to the Object Position and Static Object nodes, to use the geometry translation as the pivot. Turn this on to get more accurate off-origin velocities when Use object transform is on.
The Deforming Object shelf tool now turns off Use object transform when the collision object has no object-level scaling.
The Collision Source geometry node is now not time dependent if its input isn’t time dependent. This makes the Deforming Object shelf tool faster for static geometry.
Volume sample mode for importing collision SDFs in the Static Object DOP when Use object transform is off is now faster.
The Deforming Object shelf tool now automatically unpacks packed geometry.
Constraints - The Constraint Network node now generates warnings if any required attributes are missing, instead of silently failing. Constraint networks now support the anchor_id attribute when attaching constraints to RBD Packed objects.

Engine 2.0

Thin Client
Houdini Engine 2.0 separates the API front end from the compute back-end which has the following benefits:
Multiple Sessions per Host
Benefits Hosts with multiple threads
Greater stability to the host
Even easier to integrate - library conflicts no longer an issue
Maya Plug-In
Added support for ramp parameters.
Added support for outputting and inputting Houdini groups (as Maya sets). This allows selection-based modifications.
Materials are now preserved when returned by the Houdini Asset.
Added support for Maya 2016.
Added support for color and velocity volume types.
Added support for multiple UVs for input meshes.
Houdini geometry attributes are now supported as Maya attributes.
Hair systems can now be pushed into HEngine as curves.
Improved simulations support: Houdini variables like $FPS, $FSTART, and $FEND will match the Maya scene.
Improved curves support: Added ability to marshal in curve meshes.
Unity Plug-In
Improved painting support for both input assets and intermediate results.
Added options to auto-generate per-triangle UVs and Lightmap secondary UVs on meshes that do not get these UVs from Houdini.
Added texture gamma control.
Unreal Plug-In
Beta Testing Continues. Planned release in mid-November 2015
Baking instances
Supporting multiple variations asset instances
UE 4.9 support
Asset connections
Transform handles support
Copy / Paste of assets
Multiparm support
Support for normal maps in materials
Folder type parameters
Material baking support
Asset help display
Cooking log
3DS Max Plug-In
Available on github for testing in github.com/K240/HoudiniEngineFor3dsMax.
Houdini Engine API
Added ability to create, destroy, rename, and connect arbitrary nodes within a node network within an asset.
Added support for packed primitives.
Improved volumes support: Added ability to marshal in dense Houdini volumes.