Animating the smooth-minimum blend radius with the motion signal adapts blending to the character's pose

A fixed smooth-minimum blend radius produces a nice shoulder connection when the arm is up but hides the arm inside the body when it swings down. The solution: make the blend radius a function of the arm’s position. When the arm is up (one_minus_arm_factor ≈ 0), add nothing to the base radius. When the arm is down (one_minus_arm_factor ≈ 1), add a larger value to reduce the blend radius — keeping the arm visually separate from the body. The blend parameter thus tracks the animation signal itself, giving the shader awareness of its own pose state. This is a general technique: any SDF parameter that conflicts at extreme poses can be driven by the animation scalar that causes those poses.

Examples

float sArm = 0.01 + 0.3*pow(1.0-armFactor, 3.0); col = smin(body, arm, sArm);

Assessment

Without the animated blend radius, describe the artifact when the arm is at its lowest position. Sketch how the blend radius would need to change across a full jump cycle.