$ambientocclusion

Various WrinkleMaps maps found in Valve games for eyes and face.

Ambient occlusion is a shading method which helps add realism to local reflection models by taking into account attenuation of light due to occlusion ^[Clarify]. Unlike local methods like Phong shading, ambient occlusion is a global method, meaning the illumination at each point is a function of other geometry in the scene. However, it is a very crude approximation to full global illumination. The soft appearance achieved by ambient occlusion alone is similar to the way an object appears on an overcast day. It is globally supported on the EyeRefract shader. The IFM module, when loaded, makes the $ambientocclusion parameter function on other shaders such as VertexLitGeneric as a means of controlling the intensity of SSAO.

Todo: How does using a dedicated ambient occlusion texture differ from just baking it into the base texture (and possibly also the phong/specular mask)?

Bug:When used on transparent materials (either $translucent or $alphatest, or all materials on a model where a transparent material has been used without compiling with either $Opaque or $MostlyOpaque in the QC file), $ambientocclusion also causes the material to render the effect for any objects behind the material. (Tested in Source Filmmaker)  [todo tested in ?]

Using Ambient Occlusion

Example VMT Syntax

The following example is taken from Left 4 Dead from the model material located in L4D root/materials/models/survivors/teenangst/teenangst_eyeball_l.vmt

EyeRefract
{
	$Iris "models/survivors/green_iris2" 
	$AmbientOcclTexture "models/survivors/survivor_eye_ao" 
	$Envmap "Engine/eye-reflection-cubemap-" 
	$CorneaTexture "Engine/eye-cornea" 
	$EyeballRadius "0.6" 
	$AmbientOcclColor "[.4 .4 .4]" Default 0.33, 0.33, 0.33
	$Dilation ".5" 
	$ParallaxStrength "0.25" 
	$CorneaBumpStrength ".5" 
	$halflambert 1
	$nodecal 1
	$ambientocclusion 1
	
	$RaytraceSphere 1 
	$SphereTexkillCombo 0 
}

VMT Parameters

$AmbientOcclusion <float>

Controls strength of Ambient Occlusion. (1 = fully enabled, 0 = fully disabled)

Note:Used to control the strength of the SSAO for models in Source Filmmaker.

$AmbientOcclColor "[.n .n .n]"

Replacing n with a number of the color (RGB format)

$AmbientOcclTexture "path/to/vtf"

Filename of the ambient occlusion texture to use

Todo: How does $ambientocclusiontexture fit in with all of this?

See also

• Phong Materials
• $phong
• $basetexture
• $envmapmask (specular mask)
• $envmap (environment map)
• $selfillum