I'm using Blender 2.77 and I have currently arrived at the native Blender Renderer engine, and I fully want to understand how it works and how I can use, adapt, modify it for my own Blender projects.

I've already read many free e-books, articles and watched many videos about it, but I want to be able to truly understand AND visualize its inner workings.

Unfortunately the official Blender Render manual does not offer much in-depth/under-the-hood insight on how stuff really works.

QUESTION: - What ARE the World: Horizon, Zenith and Ambient colors? Are they real light sources (which gets internally ray-traced) or simply visual overlays which gets mixed onto the camera image?

  • $\begingroup$ Too many questions for a single post. Please use the edit link at the bottom of your question (i.stack.imgur.com/lXFuK.png) and make it so there is only one concise and focused question. For all of the other questions make more posts. One question per post is how this site works. To understand how to make better use of this site please take the tour and read through the help center section. Particularly How do I ask a good question? and What types of questions should I avoid asking? $\endgroup$
    – user1853
    Feb 14, 2018 at 5:48
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    $\begingroup$ Thanks for your very rapid feedback Cegaton! Do I understand you correctly that I need to break up this <big> question into 8 little single topic questions? $\endgroup$ Feb 14, 2018 at 5:56

1 Answer 1


Ambient Color: The Ambient color is a constant color added to the reflection model. Light sources are summed together and used in the calculation of the diffuse and specular part (See Phong reflection model for details)

phong reflection = diffuse + specular + ambient

Horizon Color: The color to use when the raytracer does not find any intersection for the primary ray (direct ray from the camera). It does not influence the shading at all. You can see this as a sort of background underneath your render.

Zenith: When using sky_blend the background will blend from the Horizon Color to the Zenith. This is done by the output pixel coordinate so the result will be the same for all camera angles and positions.

So the Horizon Color and Zenith, that generates the background, can be seen as an underlay.


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