lasm@xxxxxxxxxxxxxx writes: > What he is suggesting is to invert the color value, so white > becomes black, and black areas become white, so that the bumpmap > will take a different height field to achieve the "inverse" effect.. > I have tried it before but do not quite like the result.. > > IMHO, the PS Lighting effects did it more "politically correct". > If you press the "inverse bumpmap" there, the effect is different > from the "Invert" Bump Map in Gimp.. Just try it out yourself and > see if you agree... don't ask me to explain, I can't .. ;-) The Bumpmap plug-in works by taking the intensity values to be height values and computing the surface normal at each point. Then it does simple Gouraud-like shading on the destination image. Inverting the bumpmap source is exactly the same as using the "invert" button on the plug-in's dialog box; the intensity values are inverted and the surface normals will point in the opposite direction. I.e. it is essentially a cheap embossing effect. Photoshop's Lighting Effects produces much better results because it actually does Phong shading of the image, and it general it has better lighting models that you can choose. You can do this in the GIMP with Tom Bech's plug-in of the same name. Federico
