PaintBlob

An ice surface using the PaintBlob shader

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PaintBlob is a pixel shader available in all Source games since Portal 2. Originally intended for Gel blobs, it can also be used to create realistic hollow ice surfaces, by piercing light through it using normal mapping, and calculating light reflection from its inner layer(backface) onto the outer layer (front face). The final output color of the surface is computed by combining various lighting terms. Also supports fresnel translucency when viewing the surface through itself, creating the illusion of a hollow ice material. Furthermore, a bounding box min and max value can be set to define how "hollow" or "thick" the material surface should be.

Note:$nocull is not needed for this shader to function properly, however, can be used to visualize the $interior effects on the backface.

Todo: Report anomalies and bugs

Bug:Non-functional in   [todo tested in?]

Ice Interior Shading Algorithm

Sphere on the left has $interiorlayer 0. Sphere on the right has $interiorlayer 1

The code implements an ice interior shading algorithm to simulate the appearance of ice as a translucent material. The algorithm takes inputs such as the world normal, eye direction, and screen position and uses them to create the illusion of light passing through the surface. The final result is a composite of the blurred enviroment map, the interior color and ambient lighting.

Todo: Add images displaying screen position based fresnel refraction, can't seem to get this to work anymore.

Supported Parameters

Textures & Masks

$basetexture

Diffuse texture.

$normalmap

Normal map.

$envmap

Specular reflection.

$lightwarptexture

1D ramp texture for tinting scalar diffuse term.

$backsurface <boolean>

Specify that this is the back surface of the ice.

Bug:Results in a pixel shader crash if true.  [todo tested in?]

$specmasktexture <texture>

Mask texture for specular reflection.

$fresnelwarptexture <texture>

1D ramp texture for controlling fresnel falloff

$opacitytexture <texture>

Typically, a grayscale texture that defines the opaque and translucent parts of the texture.

Tip:Extremely useful in creating realistic scratches on an ice surface.

Outer Layer Parameters

$diffusescale <float>

Scales the output color.

Tip:Can be used to brighten the textures.

$phongexponent and $phonexponent2 <float>

Specular exponent values.

$phongboost and $phongboost2 <float>

Specular boost values.

$rimlightexponent <float>

Rim light exponent.

$rimlightboost <float>

Rim light boost.

$basecolortint <vector3>

Base texture tint.

Todo: Figure out why this doesn't work.

Interior Volume Parameters

$interior <boolean>

Enable interior layer.

$interiorfogstrength <float>

Fog strength (scales with thickness of the interior volume).

$interiorbackgroundboost <float>

Boosts the brightness of bright background pixels.

$interiorambientscale <float>

Scales the ambient light in the interior volume.

$interiorbacklightscale <float>

Scales backlighting in the interior volume.

$interiorrefractstrength <float>

Strength of bumped refract of the background seen through the interior.

Additional Parameters

$uvscale <float>

UV projection scale. Default: 0.02.

$bumpstrength <float>

Bump map strength.

$fresnelbumpstrength <float>

Bump map strength for the fresnel term.

$translucentfresnelminmaxexp <vector3>

Fresnel range parameters for the opacity texture.

$uvprojoffset <vector3>

Center for UV projection.

$bbmin and $bbmax <vector3>

Todo: Functional?

$contactshadows <boolean>

Darkens the shading of the ice region in areas where it is in contact with a surface.

$bumpframe

Bump frame.

$alphatest

Tip:Has no effect on the alpha, but effects shadow casting

$translucent

Tip:Has no effect on the alpha, but effects shadow casting

$surfaceprop

$nocull