Whitecaps object

Emits particles from the leading edges of a Particle Fluid wave, when the sharpness of the wave crest reaches a certain threshold.

See also: Particle Fluid Object, Particle Fluid Surface

This tool emits particles from the leading edge of a surface created from a Particle Fluid simulation that has been surfaced using the Particle Fluid Surface. It is useful for creating foam on the top of a moving wave.

This tool extracts the curvature of the wave, births particles, and creates a particle simulation. Particle emission is based on the curvature and velocity magnitude of the surface points, as it emits particles from the high curvature of the leading edge and inherits the velocity of the wave as it moves along with it.

Note

You can use the tools on the Drive Particles shelf to alter the particle network.

Using Whitecaps

  1. Click the Whitecaps tool on the Liquid tab.

  2. Select a particle fluid object and press Enter to complete your selection.

Note

This tool will also work with geometry that contains a velocity surface attribute, such as geometry read in with a File SOP.

Parameters

Point Samples

The number of points that are used to sample the curvature of the fluid surface.

Magnitude Threshold

Minimum

The minimum velocity magnitude threshold to emit particles.

Maximum

The maximum velocity magnitude threshold to emit particles.

Source Rate

Controls the number of particles that are emitted.

Sample Points

The number of particles is equal to the number of sample points that have a magnitude in the threshold range.

Specified

The number of particles is always equal to the specified number.

Sample Multiplier

Scale the number of samples used to emit particles when emitting from Sample Points

Specified Rate

Specify the number of particles to be emitted.

Material

Material

Path to the Material node.

Render

Display

Whether or not this object is displayed. Turn on the checkbox to have Houdini use this parameter, then set the value to 0 to hide the object, or 1 to show the object. If the checkbox is off, Houdini ignores the value.

Phantom

If enabled, this object will only cast shadows and reflections.

Renderable

Allows this object to be rendered in Output Drivers.

Shading

Categories

The categories defining the set membership of this object.

Reflection Mask

Space-separated list of objects to appear in reflections on this object. You can use wildcards (for example, prop_*) and bundle references to specify objects.

You can also use the link editor pane to edit the relationships between objects using a graphical interface.

Light Mask

Space-separated list of names of lights that illumninate this object. You can use wildcards (for example, key_*) and bundle references to specify objects.

You can also use the link editor pane to edit the relationships between lights and objects using a graphical interface.

Sampling

Geometry Velocity Blur

If enabled, this object’s rendered motion blur will be based upon the vector attribute named “v” in the geometry. The units of the attribute are in (1 unit/sec).

Velocity motion blur should be used if it contains changing point counts since it cannot be rendered correctly with deformation motion blur. For example, a particle system with changing particle counts should use this option.

You can use Velocity blur on these types of objects as long as they have valid “v” attributes. Particles automatically have the “v” attribute so if you are rendering particles, simply enable this parameter.

Dicing

Shading Quality

Shading Quality is used by micropolygon rendering to control the shading resolution. A value of 1 means that approximately 1 micropolygon will be used per pixel. A higher value will generate smaller micropolygons meaning more shading and sampling will occur, but the quality will be higher.

Ray Shading Quality

Ray Shading Quality is used by raytracing when rendering. When raytracing subdivision surfaces or patch surfaces (eg. NURBS), geometry dicing will occur similar to micropolygon rendering. This value functions similar to Shading Quality for these primitives when raytracing.

Note

Only when rendering subdivision surfaces and patch surfaces (eg. NURBS) will this setting have an effect.

Geometry

Backface removal

If enabled, geometry that are facing away from the camera are not rendered.

Procedural Shader

Geometry SHOP used by the renderer to generate render geometry for this object.

Polygons As Subdivision

If enabled, polygon geometry rendered from this object will be rendered as a subdivision surface.

Render As Points

By default, points within particle system primitives are rendered as sphere primitives. Furthermore, if a point is not part of a particle system primitive, then it is not rendered. If this parameter is enabled, then all points (regardless if they are part of a particle system) from this object’s geometry will be rendered as point (circle) primitives facing the camera plane.

Metaballs as Volume

If enabled, metaballs from this object will be rendered as volume primitives.

Coving

Coving is the process of filling cracks in diced geometry at render time, where different levels of dicing side-by-side create gaps at T-junctions.

The default setting, Coving for displacement/sub-d, only does coving for surfaces with a displacement shader and subdivision surfaces, where the displacement of points can potentially create large cracks. This is sufficient for more rendering, however you may want to use Coving for all primitives if you are using a very low shading rate or see cracks in the alpha of the rendered image.

Do not use Disable coving. It has no performance benefit, and may actually harm performance since Houdini has to render any geometry visible through the crack.

This setting only applies to micropolygon rendering.

Automatically Compute Normals

If enabled, smooth normals will we computed at render time if the normal (“N”) vector attribute does not exist.

Usages in other examples

Example name Example for