Vertex Animation Textures are an alternative method for playing back complex simulations in your game engine. The advantage to these textures is that they are read from the GPU making them ideal candidates for playing back complex animation. The downside is in order for the results to be accurate, these textures need to be uncompressed which can take up signifcant memory.
Parameters ¶
User Interface
Simple (Default) shows a limited UI of the parameters that would be changed the most often. Normal is a fully expanded UI with more in-depth but less used controls.
Start/End
This is the begining and end frame of the export. Please account for the one frame offset of the start frame to the end frame. By default the exporter will break the dynamic variables on creation.
Render With Take
If you are using takes you can change the exporter options.
Method
What primary method to export for:
Soft - Consistant Topology throughout the Simulation.
Rigid - Packed Primitive style Rigid Body Simulation.
Fluid - Changing Topology throughout the Simulation.
Sprite - Camera facing cards, points moving through space.
Engine
Set the scale, texture type and coordinate system specific to the game engine chosen.
Initialize for Engine
Applies the preset option for each engine. Make sure to do this as soon as possible as the result will overwrite parameters in the UI.
SOP Path
The path to your geometry in sops.
Data For Realtime Material ¶
Note
Any value that needs to be copied to your game-engine material has a copy button next to it.
Frame Range
The number of calculated frames. Your last frame minus your start frame. This value will be set by a script when you click Render.
Speed
The rate in houdini of your frames per second divided by your frame range. In your engine this may vary if your frame rate is different or varying. This value will be set by a script when you click Render.
Position Min/Max
Copy these values to the material in your game-engine to expand normalised position values back to their original range.
Pivot Min/Max
Visible when the Rigid method has been chosen. Pivot values are stored in the vertex colour. Most game engines will clamp these values between 0 and 1. Copy these values to the material in your game-engine to expand normalised pivot values back to their original range.
Scale Max/Min
Visible when the Rigid method has been chosen. Remaps the max and min scale over the course of the entire time range.
Width/Height
Visible when the Sprite method has been chosen and the Engine is set to Unity. Set width and height from houdini for your sprite scale.
Active Pixels
When Pad to Power of 2 is activated these values represent the pixel dimensions of the original texture. These value will be set by a script when you click Render.
Padded Size
When Pad to Power of 2 is activated this is the smallest power of 2 value for each axis. The material will use these numbers to calculate a ratio for the uv lookup. These value will be set by a script when you click Render.
Normalize data range to 0-1 space
If you intend to use texture compression then normalized data is required for your texture maps.
Pack normals into Position Alpha
Stores the normal data in the alpha channel of the position map to save texture space. This method will result in less accurate normals.
Pack Pscale into Position Alpha
Stores the pscale data into the alpha channel of the position map to save texture space.
Pad to Power of 2
When activated all textures will be exported to the nearest power of 2 value in each axis. Power of two textures allows for texture streaming on the GPU.
Double Textures (Higher Precision)
If your engine is limited to 8bit textures, a second texture can be used for higher precision.
Target Texture Size
This is the maximum width of your texture. The height is dictated by the number of frames of your animation and the number of vertices relative to your maximum width.
Target Prim Count
This is the maximum number of triangles that will be used for your fluid export mesh. Ideally this number should be less than the triangle count of the input mesh.
Calculate Optimal Primcount
This will set the target prim count value to the total number of triangles on the current frame of the input mesh.
Paths ¶
enable_project
Enable asset name override.
Project
Your parent project directory, by default this is the $JOB for those studios that use it.
Component Enable
This allows you to override the Asset name in the file path. This is typically 'opname(“..”)', the parent node of this sop area. This allows you to copy and paste this render object or unique asset as many times as you need. If within a subnet this will reflect the subnet name.
Component
By default this will refer to the name of the parent object, or subnet of this node, so you can perform a lot of copy and paste name space tricks to duplicate assets. If you need you can override the Asset name and enter any string or expression you need in there.
enable_geo
Enable export of geometry.
Geometry
Path on disk to save the geometry.
Browse Path
Opens an explorer window to the listed directory
enable_pos
Enable export of position.
Position
Path on disk to save the position map.
Position2
If Double Textures is enabled, the path on disk to save the second position map.
enable_rot
Enable export of rotation.
Rotation
Path on disk to save the rotation map.
enable_scale
Enable export of scale.
Scale
Allow your exported mesh to have pre-scale to the mesh, besides defaulting at origin.
enable_normal
If disabled Normal is packed into Alpha. Enable export of normal map.
Normal
Path on disk to save normal map, when not using the packed normals in the alpha of the position map.
Export Color Map
Enable export of color.
Color
Path on disk to save the color map.
Update Mat
Enable export of material instance for engines that support it, and this will update the values in the material instances for engines that allow it.
Material
The copy and paste material code for the engine.
Create Data
Enable export of data for the realtime shader to a json library so you can source control it.
Realtime Data
Path on disk to save the data for the real time shader.
Create Shader
Enable creation of the shader for engine that allow it.
Shader Path
Path on disk to save the shader.
Settings ¶
Initialize Simulation OPs
Triggers all simulation contexts to run in the cook chain prior to export.
Equalize Edges
For fluid exports. This will even the edges of the triangles for the best compression.
Reverse Normals
Reverses the normals on the mesh. Helpful for one sided meshes like sprites.
Convert to Image Format’s Colorspace
This removes any sRGB lookup that are default for the formats.
Raster Depth
This will be set when Initialize for Engine is clicked. Adjust the bitdepth for the image to be exported.
Black/White Points
The min and max pixels values for the exported image. This does not remap the textures to fit.
BC 4Channel Split
Renders the channels separately for different data formats.
Position Coord
This will be set when Initialize for Engine is clicked. Re-order the components for different coordinate systems.
Color Coord
Re-order the components for different coordinate systems. For color this maybe be helpful if you are hijacking this map for other purposes besides color.
Name
The name of the geometry object to be exported as, as opposed to being called MESH.1
Position ¶
Translate
Allow your exported mesh to have pre-transform to the mesh, besides defaulting at origin.
Rotate
Allow your exported mesh to have pre-rotation to the mesh, besides defaulting at origin.
Pivot
Allow your exported mesh to have pre-pivot to the mesh, besides defaulting at origin.
Delta (P.xyz)
The expected position attribute coming into the exporter.
Normal (N.xyz)
The expected normal attribute coming into the exporter.
Rest (rest.xyz)
The expected rest attribute coming into the exporter.
Rotation (orient.abcd)
The expected rotation attribute coming into the exporter.
scale (scale.xyz)
The expected scale attribute going to the engine.
pscale (pscale.x)
The expected point scale attribute coming into the exporter.
Pivot (pivot.xyz)
The expected pivot attribute coming into the exporter.
Color (Cd.xyz)
The expected color attribute coming into the exporter.
Alpha (Alpha.xyz)
The expected alpha attribute coming into the exporter.
Delta (P)
The expected position attribute going to the engine.
Normal (N)
The expected normal attribute going to the engine.
uv (uv.xy)
The expected uv attribute going to the engine.
Tiling Coord (uv2.xy)
The expected uv2 attribute going to the engine.
uv3 (uv3.xy)
The expected values going to the engine.
pscale (P.w)
The expected point scale attribute going to the engine.
Pivot (Cd.xyz)
The expected pivot attribute going to the engine.
Color (Cd.rgb)
The expected color attribute going to the engine.
Alpha (Cd.a)
The expected alpha attribute going to the engine.
Sample Shader Code ¶
Note
For Unreal Engine: Use the copy button to copy code that can be pasted into a material function. This will not work correctly if pasted into a material.
Note
For Unity: Shader files are automatically created in your project path if the Shader Path option has been enabled.
Scripts ¶
Pre-Render
Run this code before any rendering.
Post-Render
Run this code after all rendering.
