View Full Version : Bump Map Question - Can you limit positive/negative values

07 July 2010, 06:58 PM
Trying to isolate the negative value of a bump map, since i don't want any positive bump value coming through. I have a map which has a great deal of detail, but is giving me detail I dont want on the raised side of the bump map, but giving me some nice detail in the concave areas. I figured there has to be a node or way of canceling out the positive value of a bump map...

any ideas?

07 July 2010, 07:51 PM
It is my understanding that most packages provide a "clip" node that will attenuate any numeric value that falls outside of a certain numeric range.

Depending on your package, the map-values might be expressed in such a way that you can treat the data as a "color," in the sense that the value of each point in the map is a 4-tuple such as "(R,G,B,A)" even though the values do not actually correspond to "color." (The computer doesn't really know or care.) Therefore, you might find that you have considerably more expressiveness than simply to "clip" the data that's coming through. You might find a way to exert considerably more finesse than that... reshaping it using a set of curves, lots of things maybe ...

For instance, you might approach the problem by figuring out a good way to convert the bump-values into a mask, in which all of the "negative" values have (say) a 1.0 in the mask, and all "positive" values have (say) 0.0. Such a mask, applied to the bump data, would be one way to exclude all of the vectors that you do not want to consider...

Node-based systems give you a lot of ways to address a particular problem. Be creative. (Nodes are one of the most "creative" tools you have in your entire toolbox... "TMTOWTDI" = There's More Than One Way To Do It.)

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07 July 2010, 07:51 PM
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