A depth map is a pass that stores deep information at every point in a scene. Some productions use depth maps rendered in a special depth map format. Other productions use simulated depth maps that are rendered as standard image files like all other passes, but with a depth fade effect over objects with constant white shading.
Passes can be rendered sequentially by rendering different modified versions of a 3D scene, or some software solutions can be set up automatically or render more than one pass type at the time.
Possible application areas.
Here you will find 10 different application examples, which is why scenes in different passes are divided in professional work.
Changes can be made with little or no rendering. Often only one element needs to be re-rendered instead of a whole environment. Other settings, such as setting the darkness of a shadow or the color of a light, can be done without rendering again by simple adjusting the compositing.
Still images can sometimes be used for some elements, especially when the camera is not moving. For example, a still image of a room could be composed behind each frame of a single rendered animated character.
Recycling is often possible when a separate element is reused in different positions or times within a shoot.
The reflections can be softly blurred in compositing so that an anti-aliasing or a high-quality reproduction of the Reflection Pass is not necessary.
Particles can be used to create different effects in compositing. For example, if you want a natural refraction or thermal wave effect from your particles, you can render them as a separate effect pass and use the rendered particles as a mask for a glass distortion filter or as distortion of the background plate behind it.
Bump mapping can be applied selectively to Reflections, Beauty Pass, or Highlight Pass instead of having the same bump map on each element of the shader.