Build an Interactive Particle Trail

Emit discrete motes per unit of pointer travel, spread them across the entire segment, and recycle a fixed GPU pool. Reach for ambient-section-particles when particles are primarily autonomous atmosphere; reach for add-shader-cursor-trail when the output should be a continuous fluid or shader ribbon. Use this Skill when individual grains must react to the gesture.

Extracted from inner-green-3d.html, where a pointer had to lift pollen off a procedural moss root without a fast sweep leaving gaps or a resting cursor pumping a bright clump.

Resolve the interaction plane

Convert the pointer into normalized device coordinates, raycast from the camera, and intersect one stable plane near the visual surface. Reuse that hit for all interaction systems.

Reset the previous hit when the pointer leaves or the ray misses. Otherwise re-entry draws a long diagonal from the stale exit point.

For a curved visible surface, either intersect the real collider or place the response plane just in front of it. Do not raycast every decorative blade or particle.

Emit by distance

Spacing, not time, is the mechanism: