That's all correct madcoo !
Here are some details, I hope they will help for clarification, as opposed to confusion
Bump maps, exponent maps, displacement maps are called "scalar" maps. Blend maps also, off the top of my head.
Why scalar ? Because their data is not used for a direct visual effect, like they would for albedo or specular reflectivity for instance.
They are just providing a multiplier (changing over the surface) to control a given shading parameter. As you know, for an uniform effect over the surface, no need to create an uniform map, a single float value is enough (that's common for materials blendind).
So, "scalar" because they often just give the scale, or variation, of the parameter. The "b" value of the texture is giving the maximum allowed value of the effect; b-c
is the real amplitude of the map as a whole.
You can indeed understand that darker pixels will code for a smaller value of the parameter.
Practical example (displacement):
We want to evaluate the height of a displaced surface directly above a given pixel of a texture. That pixel is, say, 48% grey. The map "b" value is 0.016 (meters), it's "c" value is 0.004.
The displaced height above that pixel will be:
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(0.48 x 0.016) + 0.004 = 0.01168 meters
You can see that the texture (= file) is giving only one of the three terms of the equation. The whole thing is the map
ping for a control, namely displacement.
This is how Indigo handles texture files in most cases, if not all. Hopefully you can now predict the effects of complex parameters, like the above.
Or, that will come