pAvoid

pAvoid normally sits between pEmitter and pRender. The wire before pRender carries particle data rather than RGBA pixels: pAvoid modifies the motion of existing particles, then sends a particle stream to the next particle tool.

Distance and Strength are the core pair. Distance defines how far from the Region a particle begins trying to change course. Strength defines how strongly it tries to move relative to that Region. Tune Distance first, then Strength, so an abrupt force is not being used to compensate for a late response.

Positive Strength produces avoidance. Negative values are explicitly supported and reverse the behavior, causing particles to move toward the Region. This lets pAvoid act as a simple attraction field without changing the particle-chain topology.

pAvoid creates a desire to steer away rather than a hard physical wall. If incoming particle velocity and momentum overpower the combined Distance and Strength response, particles can cross the Region. When collision must be enforced, compare pBounce or other collision logic instead of simply pushing Strength to extremes.

The Conditions tab decides which particles are eligible; it does not define the Region. Probability is evaluated for each particle on each frame. A value of 0.6 therefore does not permanently select one fixed 60 percent subset for the particle lifetime; the same particle can be affected on one frame and not on the next.

Start/End Age limit the behavior to a normalized portion of particle lifespan. This makes phased behavior possible: particles can fly freely when young, react to pAvoid through the middle of their life, and stop reacting again near death.

Set Mode addresses particle Sets. Ignore Sets disregards the checkboxes, Affect Specified Sets limits the tool to checked Sets, and Ignore Specified Sets excludes the checked Sets. Those Sets must be assigned upstream by particle-creation or set-changing tools; pAvoid's Set checkboxes do not create new particle groups.

Region selects the geometry used by the behavior: All, Bezier, Bitmap, Cube, Line, Mesh, Rectangle or Sphere. This is not a generic image Effect Mask. Line uses two endpoints, Rectangle is a plane with no volumetric Z depth, Sphere and Cube are 3D regions, and Bezier provides a user-shaped contour.

pAvoid does not have a permanent blue Region/Mask socket. By default the node exposes only its orange particle input. Selecting Bitmap creates a dynamic Region input for a 2D image/selectable channel; selecting Mesh creates the dynamic Region input for 3D mesh data. The socket can appear green or magenta depending on which region mode establishes it.

Bitmap and Mesh therefore differ fundamentally from built-in Line, Rectangle or Sphere regions. Built-in geometry is created from pAvoid's own Region controls and needs no extra cable, while Bitmap/Mesh receives Region data from another Flow branch.

Line is especially useful for learning pAvoid. Start and End expose X/Y/Z positions and can be connected to Paths or Trackers when required. It makes the response boundary easy to see conceptually while Distance defines a wider zone in which steering starts.

In production, pAvoid is useful for gently steering particles around graphics or geometry, creating exclusion zones, separating a flow around a boundary, or creating attraction with negative Strength. Always judge the final result in playback because incoming speed, Probability and other particle forces all evolve over time.