Today we’ll look into Blender Internal materials settings that can cause render times go up.
With materials, same as with lights, the more we try for realism, the more complex and slow computations become. In Blender Internal, raytraced reflections make objects come to life but kill the render speed.
In real life, most materials are not 100% diffuse or reflective but have some degree of roughness that disperse the light and give a soft, blurry reflection. In Blender this can be achieved in some way by bump mapping but the glossy setting in the reflection panel takes this one step further, allowing for really nice realistic surfaces.
This effect is achieved by a method that uses sampling, so less samples means a grainy, noisy look, more samples a smoother, nicer look – at the expense of long render times. Starting with less samples (the default of 18 looks acceptable) and increasing as needed before the final render is a good idea.
The other materials property we’ll take a look at is transparency. In Blender Internal we can try using Z-transparency when real glass properties are not needed, like in alpha mapped planes or flat glass surfaces. Z-transparency does not offer optimization settings.
Raytraced transparency is more realistic, simulating effects like refraction and blurred transparency, but renders slower. The overlaying of several transparent objects in a complex scene can also cause problems with render times. Try changing the Depth setting to reduce the number of transparency layers to be computed. All transparent objects outside the Depth range will be rendered as opaque.
The glossy setting in the transparency panel works the same as the one in reflections, increasing samples for a smoother appearance will also increase render times.
Know any other tips? Let us know in the comments.
