float4 delta = pos2-pos1; float r = SQRT(delta.x*delta.x + delta.y*delta.y + delta.z*delta.z); COMPUTE_FORCE
dEdR = (r > 0.0f) ? (dEdR / r) : 0.0f; delta.xyz *= dEdR; float4 force1 = delta; float4 force2 = -delta;