Displaying Photons in the Render Region

Once you have set up the light and defined the casters and receivers, it is time to see some results in the render region. Because they take longer to render, they are turned off by default. To view the global illumination and/or caustic effects in the render region, follow these steps:

1. Create a render region in a viewport (press Q and draw). Make sure you include the area where caustic or global illumination effects are displayed.

2. Do one of the following:

   • To show photon effects in all render regions, choose Render Regions All Options from the Render toolbar to open the View Render Options property editor.

     or

   • To show photon effects in a specific region, click the triangle at the upper left of the regions (or right-click on the region's border) and choose Options.

     or

   • To show photon effects in the last viewport you clicked in (highlighted with a white border), choose Render Regions Active Viewport Options.

3. On the GI and Caustics tab of the mental ray Render Options property editor, activate Enable for Caustics and/or Global Illumination. The selected effect is now visible in the render region.

   NoteThe first time a scene's photons are rendered in the render region takes a little longer than subsequent renders. This is because the Photon Map is being calculated for the first time.

   From this tab, you can also set the Caustic Accuracy, Global Illumination Accuracy, and various Photon Depths for your render. For information on photon rendering options, see Preparing Global Illumination and Caustics for Rendering.

4. To modify the display of caustics in the region, you can generate a map of the caustic effect by selecting the Rebuild Photon Map option. For more information, see Rebuilding the Photon Map.