Defining a Light as a Photon Emitter

To define a photon light source

1. Select the light you want to use as the global illumination or caustic source. Photons can be emitted from point lights, spotlights, or area lights.

2. Choose Modify Shader from the Render toolbar to display the selected light's property editor.

3. On the Photon tab, display all of the light's photon properties.

4. Deselect Light Falloff while setting up the light source. You can select it again later.

5. Define the light as a Global Illumination source or a Caustic source (or both) by selecting the appropriate option.

6. Define a custom Color for the global illumination or caustic light by using the color sliders or the Color Editor (click the color box beside the light color sliders).

   For more information on defining colors, see Defining Color Properties [Commands and Tools].

7. Set the caustic energy Intensity for the light. Intensity is the option that creates the caustic effect. You can tune the brightness of caustics to make them either more or less visible by setting a value from 10 000 to 1 000 000.

   Note

   It is important to understand the difference between color and intensity:

   • Color is the power of the direct illumination.

   • Intensity is the power of the caustic.

   You set the color of the actual light in the light property editor, but the caustic light color does not affect the color emitted by the light itself.

8. Define the number of Emitted Photons for your caustic or global illumination effect using this slider. Keep in mind that the higher this value is, the longer it takes to render.

   This value specifies the number of photons in the Photon Map (see Using Photon Maps), so it's a good indication of the quality of the generated caustics. It is also a direct indication of the memory usage, which is proportional to the number of photons in the Photon Map.

   • For quick low-quality caustics, values of 1000-10 000 are adequate.

     Lower values, in the case of global illumination, cause fuzzy puddles of light — this means there are too few photons hitting the surfaces in the scenes. In the case of caustic effects, the caustic looks blurry or indistinct.

   • Medium-quality typically needs 100 000.

   • Highly accurate effects may require up to 1 000 000.

9. The photon effect is not be visible just yet. You must define receivers and casters and then enable photons in the render region. See the next section, Setting Photon Casting, Receiving and Visibility, for the next step.