$blendmodulatetexture is a material shader parameter available in all Source games since Source 2006 for
WorldVertexTransition. It changes the transition between the textures from a smooth, linear gradient to one "stamped" with a pattern.
You should use
$blendmodulatetexture wherever possible, as the improvement in visual quality is immense!
- Incompatible with $normalmapalphaenvmapmask (use $envmapmask instead).
- In Source 2006/2007 and Team Fortress 2, incompatible with $basetexturetransform and $detail.
- In Source 2006, incompatible with $envmaptint and $envmapmask.
- In Alien Swarm, modulation textures are not aligned correctly. Use
$blendmasktransform "center .5 .5 scale 1 -1 rotate 90 translate 0 0"to fix them up.
In some cases, textures will blend as if $blendmodulatetexture were not used:
- Does not display when viewed through water. To do: Only in earlier games?
- Does not display when illuminated with player's flashlight in Half-Life 2. This is fixed in Mapbase.
- Does not display in the Hammer Editor in most games. Known exceptions include Counter-Strike: Global Offensive, Portal 2, Garry's Mod, and Mapbase.
- The modulation texture for the blending. See below for more details.
- Transforms the modulation texture before use in the material.
- The default position is
"center .5 .5 scale 1 1 rotate 0 translate 0 0".
centerdefines the point of rotation. Only useful if
rotateis being used.
scalefits the texture into the material the given number of times. '
2 1' is a 50% scale in the X axis.
rotaterotates the texture counter-clockwise in degrees. Accepts any number, including negatives.
translateshifts the texture by the given numbers. '
.5' will shift it half-way.
- Note: All values must be included!
- Bug: Scaling the texture may cause odd issues where the Texture Lock tool in Hammer will not actually lock the texture in place.
- Bug: Rotating textures applied on brushes will rotate around the map origin (confirm: Orangebox engine only?). A fix for this is to change the center position in the VMT to the brush's origin.
- To do: Appears to invert the blending effect
Blend Modulation Textures
Only two colour channels are read from the texture:
- Biases in favor of
$basetexture; high-value areas will be the most resistant to modulation. 128 is normal.
- The idea is to paint noise and patterns into this channel, so that the edge between the two textures becomes irregular. Valve's snow texture (see right) has lots of ragged edges in the green channel, and even some bootprints. There are also lines painted along the edges of the albedo's bricks that give them a tendency to have snow along their edges.
- Sharpens. 0 makes the transition binary, 255 effectively disables modulation.
- The red channel of Valve's snow modulation texture is a constant 99, which produces a fairly sharp falloff. Using different values in different places has the potential to produce a more complex effect.
There is not always a need for the texture to be high resolution - high frequency blends can be produced from low-res textures.