Graphics Programs Reference
In-Depth Information
The cause of color bleeding
Color bleed, as discussed in the context of architectural visualization renders, is not
the product of colored lights in a scene as per our previous exercise. Rather, it is a
phenomenon caused by the interaction of physically accurate lights, V-Ray's Global
Illumination systems, and also physically accurate materials in the scene.
In the real world, color bleed (also known as indirect diffuse illumination) is an effect
that occurs as light is bounced from one surface to another. As the light leaves one
surface, it takes a little bit of the object's diffuse coloration along with it. This is then
mixed with or added to the color of the next surface the light interacts with, and it goes
on with the travelling light essentially creating a color reflection or bounce effect.
Color bleed - exercise one
To see color bleed in action, take a piece of white, non-reflective cloth or paper and
place a strongly-colored object on it. Better still, coat a shallow box with the white
material, and place the strongly-colored object inside it. Even under average daylight
conditions, the transmission of color from the object to the white material will be in-
stantly noticeable. This is color bleed in action.
The strange thing is that color bleeding goes on all around us without our paying too
much attention to it at all. This is because the brain does a superb job of auto white-
balancing or filtering out the bounced colors, letting us see the colors that we think we
should be seeing. This is especially the case with objects that we perceive as sup-
posedly being white.
The problem with this phenomenon going largely unnoticed is that it can lead clients
who look at renders containing physically correct color bounce to ask why the colora-
tion in their beautifully crafted environment looks all wrong.
Fortunately for us, reducing or even removing the effects of color bleed in a scene is
really not that difficult a thing to do if we make good use of the tools that V-Ray gives
us. In fact, there are actually quite a few ways that we could go about reducing col-
or bleed. Some are handled from inside our scene materials, others make use of the
features available in the controls for V-Rays GI engines.
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