Poser 8 Revealed: Adding Scene Lighting - Part 2
ENABLE SHADOWS AND AMBIENT OCCLUSION
Within the Properties palette for lights are two options for enabling shadows and ambient occlusion. Shadows can add a lot to the realism of the scene and learning the various shadowing options will give you better control over how shadows appear in the scene. Ambient occlusion is a render property that can simulate the dark corners of objects that are surrounded by walls and other objects.
Shadows are computed when the scene is rendered and two methods exist for creating shadows[md]ray trace and depth map. Raytrace shadows have a sharp edge and are much more realistic because they are created by following each light ray as it bounces about the scene, but the drawback is that they can take a considerable amount of time to render. Depth-map shadows are blurrier, but they can be rendered very quickly.
Raytrace shadows will be rendered only if the Ray Tracing option is enabled in the Render Settings dialog box.
You can set the amount of blur that a shadow has using the Shadow Blur Radius setting. The Shadow Min Bias setting prevents the scene objects from casting shadows on themselves. Another way to think about the Bias setting is that it defines the accuracy of the shadows where low values (usually less than 1) have better results. However, extremely low Bias values can create lighting anomalies to object shadows. Lower Bias values also require longer render times. Figure 7-10 shows two rendered images side by side in the Render panel with Shadow Map shadows with different Blur Radius settings. Notice how the left half of the figure has a blurry shadow and the right half is clean.
If you select to use Raytrace shadows, don’t set the Bias value to 0.
If multiple lights are included in a scene, only enable shadows for one light in the scene.
Reusing Shadow Maps
If you select the Depth Map Shadows option, the Shadow Map is computed the first time you render the scene, but the shadow map is automatically saved and reused on subsequent renders to save time. To have Poser reuse the computed shadow map, enable the Render, Reuse Shadow Maps menu option.
To force Poser to render the shadow maps again, select Render, Clear Shadow Maps. Shadow maps should be re-rendered whenever the scene objects move or if the lights move or change parameters.
When a light object is selected, the Parameters palette includes a Map Size value, which sets the size in pixels of the computed shadow map. Larger shadow maps take up more memory, but have a finer resolution.