Autodesk 12812-051462-9011 User Guide 3 - Page 1054

Caustics group IMPORTANT For caustics to render, you must also make sure to set up these other conditions in your scene: ■ At least one object must be set to generate caustics. This is off by default. ■ At least one object must be set to receive caustics. This is on by default. ■ At least one light must be set to generate caustics. This is off by default. The settings for generating and receiving caustics are located on the Object Properties dialog > mental ray Panel on page 322. Enable When on, the mental ray renderer calculates caustics effects. Default=off. Multiplier/color swatch Use these to control the intensity and color of the indirect light accumulated by caustics. The defaults, 1.0 and white, produce physically correct rendering. This is useful for adjusting the contribution of the caustics effect, thus improving the quality of an image. Maximum Num. Photons per Sample Sets how many photons are used to compute the intensity of the caustic. Increasing this value makes caustics less noisy but also more blurry. Decreasing this value makes caustics more noisy but less blurry. The larger the Samples value, the greater the rendering time. Default=100. TIP To preview a caustic, set Samples to 20, then increase the value for a final rendering. Maximum Sampling Radius When on, the spinner value sets the size of photons. When off, each photon is calculated to be 1/100 of the radius of the full scene. Maximum Sampling Radius default=off; value default=1.0. In many cases, the default photon size (Radius=off) of 1/100 the scene size gives useful results. In other cases, the default photon size might be too large or too small. When photon reflections overlap, the mental ray renderer uses sampling to smooth them together. Increasing the number of samples increases the amount of smoothing and can create more natural-looking caustics. When photons have a small radius and don't overlap, the Samples setting has no effect. Low Radius values with a large number of photons result in dotty caustics. mental ray Renderer | 6309