The world-ray scale λ that moves the projected sample by the fraction kappa of
the screen shift, given the clip w at the ray's start (w0) and end (w1).
Floored at REFRACTION_MIN_RAY_SCALE; a ray that ends behind the camera
(w1 ≤ 0, where the projection is meaningless) gets the floor too.
The world-ray scale
λthat moves the projected sample by the fractionkappaof the screen shift, given the clipwat the ray's start (w0) and end (w1). Floored at REFRACTION_MIN_RAY_SCALE; a ray that ends behind the camera (w1 ≤ 0, where the projection is meaningless) gets the floor too.