Decided to learn a bit about the Light Paths nodes in Blender. Read up on it, and toyed around with a few scenes of mine

I decided to craft up a simple scene. A highly reflective plane upon which a cube sits.I decided to stick in a Light Paths node into the cube to mess around with the concept and get some practice in

The following is the material I'd made: enter image description here

The way I'd expect this to logically work is as follows: "If the incoming ray/ray that has just made contact with the object bounced off a glossy surface in the previous bounce, color the surface of the cube blue. Else, color it red"

enter image description here

As opposed to the surface being colored blue, its reflection ends up being colored blue? Why exactly did this happen? What exactly went on 'under the hood' to have caused it?

From my understanding, given Cycles is a path-tracer, the shader I'd made should only be calculated for the surface of the cube (and subsequently any reflection of it on other objects for indirect lighting and the like)

Except, only the latter has occured here. I'd expected portions of the cube where light hit it post bouncing off the plane to be blue, yet the cube in its entirety is red? What exactly am I getting wrong?


1 Answer 1


Ray tracing works in the the opposite direction of light. Instead of lights shining on the materials and some of that light hitting the camera it is the camera that shoots out rays looking for lights and things to interact with.

If we think of it this way it becomes clearer why the reflected cube is blue; it is being seen by a ray that is being reflected. If you want to read more the Light Paths chapter in the Blender Manual is pretty good.

It then also becomes possible to create a material that shows a blue cube with a red reflection that tints light that bounces of it green:

A blue cube in a box with a red reflection and green tinted bounce light


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .