Surface Test operator

The Surface Test operator tests if a particle’s relationship to a nearby surface satisfies a condition.


Objects

  • Input object list: the list of input objects to test.

Sample

  • Sample type: controls which sampler will be used to determine closest-surface proximities for particles.

Test TRUE If

Inside/Outside Volume

The test condition will be satisfied if the particle is inside/outside the nearest surface.

  • Accuracy: controls the accuracy of the raycaster used to compute information about whether a particle is inside or outside of an object’s volume.
Distance to surface

The test condition will be based on the distance between the particle and the nearest surface.

  • Less than: the test condition will be satisfied if the distance is less than a certain value.

  • Greater than: the test condition will be satisfied if the distance is greater than a certain value.

  • Value: the distance test value.

Variation: the per-particle amount of variation to apply.
Raycast/No-Raycast Intersection

The test condition will be satisfied if a raycast along a specified vector hits or doesn’t hit a surface.

  • X/Y/Z: per-axis values for the raycast vector, in world-space.
Raycast occlusion

The test condition will be satisfied the number of random rays that hit a surface is above a certain threshold (or don’t hit the surface if ‘invert’ is checked)

  • Num rays: the number of random rays to cast (higher = more accurate).

  • Length: the length of each ray.

  • Spread: the maximum divergence, in degrees, along computed surface normals that the rays will be cast.

For surface occlusion, a spread of 90.0 is best. For 3d space occlusion, a spread of 180.0 is best.

  • Threshold %: the percentage of rays that must hit a surface to satisfy the test condition.

  • Invert: when enabled, the condition is inverted (it will be satisfied if a percentage of rays above the threshold do not hit a surface).

Nearest Texture

The test condition will be satisfied if a texture sampled on the nearest point of the nearest surface satisfies a certain condition.

  • Texmap: the texture map to sample.

  • Surface offset as W: the distance from the particle to the closest surface will be used as the W coordinate in the UVW value which is used to sample the texture.

  • RGB less than: the test condition will be satisfied if the magnitude of the sampled RGB value is less than a specified value.

  • RGB greater than: the test condition will be satisfied if the magnitude of the sampled RGB value is greater than a specified value.

  • Value: the RGB test value.

  • Variation %: the per-particle percentage of variation to apply.
  • RGB is threshold: the normalized magnitude of the sampled RGB value will be used as test condition probability.

Nearest Material ID

The test condition will be satisfied based on properties of the nearest face’s material ID.

  • Less than: the test condition will be satisfied if the nearest face’s material ID is less than the specified value.

  • Greater than: the test condition will be satisfied if the nearest face’s material ID is greater than the specified value.

  • Equal to: the test condition will be satisfied if the nearest face’s material ID is equal to the specified value.

  • Not Equal to: the test condition will be satisfied if the nearest face’s material ID is not equal to the specified value.

  • Mat ID: the material ID test value.

Nearest Normal

The test condition will be satisfied based on properties of the nearest normal on the nearest surface.

  • By Object: tests whether the nearest normal is aligned to the local Z-Axis vector of some object, within the specified threshold.

  • Object: the object whose local Z-Axis will be used for the normal test.

  • By Value: tests whether the nearest normal is aligned to a specified normal, within the specified threshold.

  • X/Y/Z: the per-axis values of the specified normal.

  • Thresh: the threshold used to determine normal alignment.

Nearest Velocity

The test condition will be satisfied based on properties of the nearest surface velocity magnitude on the nearest surface.

  • Less than: the test condition will be satisfied if the nearest velocity magnitude is less than a certain value.

  • Greater than: the test condition will be satisfied if the nearest velocity magnitude is greater than a certain value.

  • Value: the magnitude test value.

Variation: the per-particle amount of variation to apply.

Uniqueness

  • Seed: the seed value for all varied parameters.