User Manual

Table Of Contents
Ambient Occlusion [SSAO]
The AmbientOcclusion node
Ambient Occlusion Node Introduction
Ambient Occlusion (AO) is the lighting caused when a scene is surrounded by a uniform diffuse
spherical light source. Think of the scene as being surrounded by a humongous sphere that
uniformly emits light from its surface. AO captures the low frequency lighting. It does not
capture sharp shadows or Diffuse or Specular lighting. So, AO is usually combined with Diffuse
and Specular lighting to create a full lighting solution.
The Ambient Occlusion node generates global lighting effects in 3D-rendered scenes as a post
effect. It quickly approximates computationally expensive ray-traced global illumination. Being a
post effect, it exposes similar aliasing issues like the Shader, Texture, and Volume Fog nodes.
Hence, artifacts may appear in certain situations.
Usage
The AO node rarely works out of the box, and requires some tweaking. The setup process
involves adjusting the Kernel Radius and Number Of Samples to get the desired affect.
The Kernel Radius depends on the natural “scale” of the scene. Initially, there might appear to
be no AO at all. In most cases, the Kernel Radius is too small or too big, and working values
must be found.
Inputs
There are three inputs on the AO node. The standard effect mask is used to limit the AO effect.
The Input and Camera connections are required. If either of these is not supplied, the node
does not render an image on output.
Input: This orange input accepts a 2D RGBA image, Z-Depth, and Normals.
Camera: The green camera input can take either a 3D Scene or a 3D Camera that
rendered the 2D image.
Effect Mask: The optional blue effect mask input accepts a mask shape created
by polylines, basic primitive shapes, paint strokes, or bitmaps from other tools.
Connecting a mask to this input limits the Ambient Occlusion to only those pixels
within the mask. An effects mask is applied to the tool after the tool is processed.
Basic Node Setup
The Ambient Occlusion node is typically placed after a Renderer 3D node. The Renderer 3D
node must have Z-Depth and Normals enabled in its output channels. The Camera3D that is
rendered by the Renderer3D node is then connected to the camera input on the AO node.
Chapter – 87 Deep Pixel Nodes 1922