My scene is a home consists of 4 walls(4 cube). I placed a light source at the same distance from the corner that joint wall 1 and wall 3 (45 degree). If I applied texture on walls, I obtain this image where the light reflected not exactly symmetrically

enter image description here

but when i delete the texture of walls, I obtain this image where the light is reflected symmetrically. How can we explain this phenomenon ? enter image description here

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    $\begingroup$ I take it you are using some kind of glossy material. The reflection will depend largely on the viewing angle... $\endgroup$ – cegaton Apr 10 '15 at 19:54
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    $\begingroup$ What do you mean by the light is not reflected symmetrically? What I see is that the light is absorbed more where the colors of the texture are darker. $\endgroup$ – Denis Apr 10 '15 at 19:55
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    $\begingroup$ And as cegaton said, diffused light will be distributed evenly, and reflection on glossy surface will change depends on the view angle, like if you are looking in the mirror. $\endgroup$ – Denis Apr 10 '15 at 19:59
  • $\begingroup$ I think this might be because the texture is actually grey, even in the lighter parts, while the plain diffuse is a consistent white. $\endgroup$ – VRM Apr 11 '15 at 0:50
  • $\begingroup$ Please accept my answer if it answers your question. If not, please comment and explain why not. $\endgroup$ – VRM Apr 14 '15 at 18:16

This is caused by the color of the Diffuse surface. A whiter surface reflects more light, while a grayer surface reflects less. The only difference between the below planes is the color, the distance from the light source and the other material options are identical.

Grey vs. White

As you can see the difference is quite pronounced. The whiter plane (right side) reflects much more light. When you use a texture to drive color, you are mixing the two of these, resulting in a more broken up diffuse shading.


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