The amount of diffuse light received from indirect sources only.
Indirect_diffuse: 0 (default) creates a more two-dimensional looking toon shading effect.
The amount of specularity received from indirect sources only. Values other than 1.0 will cause the materials to not preserve energy, and global illumination may not converge.
The toon shader is energy conserving by default. If this is disabled, the Toon shader simply adds base, specular, and transmission. Care should be taken when disabling this option as it will affect indirect illumination with the toon shader.