Autodesk 12812-051462-9011 User Guide 3 - Page 982

There's the problem: you actually have six surfaces that need to be traced by the light rays for both reflections and refractions. The way to always calculate the number of rays needed for a scene is to take the ray-traced objects in your scene and draw an imaginary line through them, originating at the point of view. Then, count the number of surfaces the line intersects. For the wineglass and wine, you need at least six reflections and refractions that correspond to the following surfaces: ■ Near outer glass surface ("near" relative to your Camera viewpoint) ■ Near inner glass surface ■ Near wine surface ■ Far wine surface ■ Far inner glass surface ■ Far outer glass surface Therefore, increase the value of Max. Depth to 12. Caustics and Global Illumination Before rendering with caustics, there are several things you need to set up in your scene: ■ For caustics to work properly, the generating object must use a material that contains some degree of shininess, reflectivity, or refraction. Assign a Raytrace or other map as either a Reflection map or Refraction map before you render caustics. ■ Most often, you'll be using very shiny, highly reflective materials (such as chrome and other metals), or transparent or translucent materials (such as glass goblets or water), to generate caustics in your scene. If you're using a glassy material, make sure it's double-sided to create the proper results. ■ Make sure you have object properties on page 322 set to Receive Caustics or Generate Caustics (or both). To set up these properties, right-click an object and choose Properties. For example, if you're rendering a wineglass on a tabletop, you probably want the wineglass both to generate and receive caustics (so that caustics are scattered within the glass itself), and the tabletop only to receive caustics (unless it's chrome, say, instead of wood). ■ If the rendering of your scene is washed out by light, double-check the Multiplier settings: one in the Basic group of the Final Gather rollout on mental ray Renderer | 6237