In the follwing article, we would like to introduce you to various rendering pass types and possible application examples like a 3D configurator in practice.
if you prefer video tutorials, we recommend that you watch the following video:
Pass-types.
A so-called beatury pass is the main color of a subject including diffuse lighting, color and color maps and usually does not contain reflections, lights and shadows that are normally separate passes.
Highlight passes isolate the highlights from their objects. You can reproduce the highlighting of light passages by turning off the ambient light and making the diffuse shading and color mapping of the object pure black. The result is a rendering of all highlights of a scene over a black background, without any other kind of shading.
A Reflection Pass includes reflections from other objects or the environment and can either replace or complement the Highlight Pass. To isolate reflections, you usually only need to turn off shading from a surface so that only reflections occur.
A shadow pass is a rendering that shows the positions of shadows in a scene. A shadow pass often appears as a white shadow area against a black background, a black shadow against a white background, or as a rendering with the shadow shape embedded in the alpha channel.
Shadow passes are shadows in which an object casts a shadow on another 3D object, for example. Separate shadow passes can be shadows where an object casts a shadow on itself, such as a shadow cast by a character`s nose on his face.
A Lighting Pass is an optional part of multi-pass rendering that gives the compositing process more flexibility and control. Instead of rendering a Beauty Pass all at once, you can render multiple Lighting Passes instead, with each Lighting Pass showing the effect of one light on a element. Other lights are hidden or deleted when the Lighting Pass is rendered.
Depending on the requirements of a project, effects are sometimes run through or rendered. An Effect Pass is a separate rendering of a visual effect or mask for a visual effect. An effect pass can be an optical effect, such as a light glow or a lens flicker. It could also be a particle effect such as a cloud of smoke or a cloud of exhaust nozzles.
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.
Glows can be created and manipulated by adding a fuzzy copy of their Specular Pass to the compositing.
You can create depth of field without additional render time by blurring separately rendered background layers or by using a depth pass as a mask for a blur filter. You can also create atmospheric perspectives with a color correction masked by the depth pass.