VfxPrimitiveCameraSegmentBeam

Inheritance 3 ancestors

• VfxPrimitiveBase
  • VfxLegacyPrimitiveBase
    • VfxPrimitiveBeamBase
      • VfxPrimitiveCameraSegmentBeamcurrent

Class Documentation

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A beam drawn as a strip bent through its particles. It spans the same two endpoints as VfxPrimitiveBeam - the system's position and the effect instance's target, each plus its offset from mBeam - but each particle becomes one rib of the strip instead of a whole quad, and consecutive ribs are joined.

Rib placement. The number of ribs is mBeam.mSegments, multiplied by an engine quality factor and truncated. A particle's place along the beam comes from its birth order, counted from the emitter's start:

t   = birthIndex / (ribs - 1)
rib = lerp(source, target, t) + the particle's offset from its emitter

The particle's own motion pushes its rib off the straight line, so velocity, drag, force fields and WorldAcceleration bend the beam. Particles that do not move draw a straight strip.

Particle count. The emitter never holds more particles than there are ribs, and only the first ribs particles it spawns are drawn. A later particle is not drawn even when it replaces one that died, so a rib whose particle dies is gone for the rest of the beam's life. With mSegments at 0 or 1 nothing is drawn.

Width. The strip always faces the camera: one width direction for the whole beam, perpendicular to the beam and to the view from the source. Each rib's width is its particle's scale.x. mBeam.mMode has no effect on this primitive.

Color. Every rib carries its own particle's color and color-lookup coordinate, so color over lifetime varies along the beam.

Notes

• Alpha erosion does not progress on this primitive: the erosion drive every rib writes is always 0.
• The color-lookup coordinate fills the slot a TextureMult layer would read its UVs from, so with a mult texture set, the mult layer samples at the color-lookup coordinate.