Houdini 20.5 Nodes Geometry nodes

VDB Rasterize Frustum geometry node

Rasterize points into density and attribute volumes.

On this page

This node rasterizes point attributes into density, mask, float, vector, and integer grids. It supports using particle radius and can efficiently choose between point, ray, or sphere rasterization algorithms for each point in a data set based on the input values.

Clipping can be performed by frustum, bounding box, or mask and is done on the volume samples, not the positions of the points.

This node accepts Houdini points and VDB points. When using Houdini points, there will be a small performance cost as the points and required attributes are implicitly converted into VDB Points for processing.

Geometry and camera motion blur can be baked into the resulting grids. Geometry motion blur is computed using a velocity point attribute, and camera motion blur is computed using an animated transform provided using the reference VDB supplied in the second node input.

Rasterizing can be performed into cartesian and frustum grids (otherwise referred to as tapered grids). For frustum grids, approximations are used by default to accelerate the rasterization. This can be disabled to achieve a more accurate result.

This node supports streaming of VDB points and attributes if one or more delayed-load VDB is provided as an input.

Parameters

Group

Specify input primitive groups to rasterize.

VDB Points Groups

Specify VDB Points groups to rasterize.

Merge VDB Points

Merge VDB Points grids during rasterization to output a single VDB volume.

Transform VDB

VDB grid that defines the output transform.

Mask VDB

VDB grid whose active topology defines what region to rasterize into. Clipping is performed based on volume samples, not point positions.

Invert Mask

Turn this on to rasterize in the region outside the mask.

Voxel Size

Uniform voxel edge length in world units. Decrease the voxel size to increase the volume resolution.

Clip to Frustum

When using a frustum transform, only rasterize data inside the frustum region.

Optimize for Memory

Keep the memory footprint as small as possible at the cost of slower performance.

Volume

Create Density Volume

Turn this on for density volume generation. Attribute volumes are still constructed as usual.

Density Scale

Scale the density attribute by this amount. If the density attribute is missing, use a value of one as the reference.

Contribution Threshold

Only rasterize attribute contribution when within this threshold.

Create Mask

If this is turned on, output a rasterization mask.

Attributes

Specify a list of point attributes to be rasterized.

Density Mode

How to blend point densities in the density volume.

Accumulated

Density contributions from each particle are summed up.

Maximum

Choose the maximum density at each voxel.

Weighted Average

Compute the weighted-average of the densities at each voxel.

Scalar Mode

How to blend scalar point attribute values (except density).

Accumulated

Contributions from each particle are summed up.

Maximum

Choose the maximum value at each voxel.

Weighted Average

Compute the weighted-average of the value at each voxel.

Vector Mode

How to blend vector point attribute values

Accumulated

Contributions from each particle are summed up.

Weighted Average

Compute the weighted-average of the value at each voxel.

Scale Contribution by Voxel Volume

Scale each voxel rasterization contribution by the volume of the voxel.

Radius

Enable

Turn this on to use particle radius.

Radius Attribute

Radius attribute (defaults to pscale).

Radius Scale

Scale the radius by this amount.

If radius attribute is missing, use a value of one as the reference.

Accurate Frustum Radius

If this is turned on, use a highly accurate algorithm to rasterize points with radius into a frustum grid at the cost of much slower performance.

Accurate Sphere Motion Blur

If this is turned on, pack spheres more tightly along the motion-blurred rasterization path to hide visible sphere artifacts at the cost of slower performance.

Motion Blur

Bake Motion Blur

Bake the motion blur of the point when applying geometry and/or camera deformation.

Shutter

The portion of the frame interval that the camera shutter is open when baking motion blur.

Shutter Offset

Controls where the motion blur occurs relative to the current frame. A value of -1 will blur from the previous frame to the current frame. A value of 0 will blur from halfway to the previous frame to halfway to the next frame. A value of 1 will blur from the current frame to the next frame.

Frames / Second

Frames-per-second to use when computing motion blur.

Motion Samples

How many motion samples to use when computing motion blur.

The default is two, which means a sample at the beginning and end of the shutter interval. Increase this value to compute more accurate camera motion blur through sampling the reference transform at a higher frequency. It can also be useful in eliminating any warping effect when applying geometry motion blur in a frustum grid. Note that motion sampling will automatically be disabled if the camera is static and frustum rasterization is not in use.

Geometry Motion Blur

Bake geometry motion blur as computed using point velocity.

Velocity Attribute

Velocity attribute to apply geometry motion blur (defaults to v).

Camera Motion Blur

Bake camera motion blur as computed using the motion derived from the reference transform.

Allow Interpolation of Camera Motion

If this is turned on, camera transform interpolation is performed when camera motion is detected not to be continuous. In certain cases, it may be desirable to disable interpolation when using complex camera motion that is known to be continuous.

Locals

See also

Geometry nodes