How can we explain texture effect on the point light 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 



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



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.