Realistic Architectural Visualization with 3ds Max and mental ray Caustics: In the Indirect Illumination tab, Caustics and Global Illumination (GI) rollout, you can enable and control the reflective or refractive caustics effects in your scene. Caustics are discussed in detail in the appendices. Note: It is advised to avoid using caustics in external scenes, as this can take too long to compute. Material Override tool Caustics and Global Illumination (GI) rollout