Specular power setting in alpha channel doesn't work currently very well.
Okay, that's what was happening. I was trying to use the alpha channel alone to change the specular power. Also, I may not have understood it well myself- it's making more sense now.
I think the "specularity" feature has been overlooked because few people know its potential. The "reflectivity" feature really completes it. Within the bounds of the diffuse texture, normal map, spec color, spec intensity, and reflection intensity, it's now possible to simulate a wide variety of paints or textures such as glossy or flat paint, metallic or solid color, duct tape, perfect mirror (Iridium satellite, anyone?), soot and dirt, wet or oily patches, etc.
I think it is a good idea to separate the specularity from the reflectivity so that each can be individually controlled.
I find it a difficult to create a textures where an alpha channel is containing some data so maybe we should consider an alternative ways to define the specular maps.
a) One channel texture (L8) that would modulate the reflected image but the color and power information would come from a meterial defination.
b) Dual channel texture (DXT1, U8V8). Red channel would modulate the reflection and green channel would modulate the specular power.
I like option b better. I think specular color and power information should come from textures, but if the textures are not present, then they could come from a material definition.
At the risk of adding too much complexity to something already complicated, would it be possible to change the reflectivity based on the camera vector relative to the normal vector, i.e. reflections around the edges of a sphere would be stronger than those on the sphere directly facing the camera?
Truly amazing work. I still have to pick up my jaw off the floor multiple times. Thank you for all the work you're doing, and for putting up with me.
---------- Post added at 04:29 AM ---------- Previous post was at 03:45 AM ----------
Use GIMP (
http://www.gimp.org/), the GIMP normalmap plugin (
http://code.google.com/p/gimp-normalmap/), and the GIMP DDS plugin (
http://code.google.com/p/gimp-dds/).
Install GIMP and both plugins by following the instructions.
In GIMP, open the diffuse texture containing the metal foil. In the "Filters" menu, open the "Map" menu, and click "Normalmap". Click the "3D Preview" button. In the window that opens, you can pan around the texture with the left mouse button, and zoom with the right. To make it easier to view the bumpy texture, turn on "Specular lighting", and set "Diffuse color" to black. Now, in the first Normal map window, start playing with settings. I like using the "4 sample" or "3x3" filters. Adjust the "scale" to get the desired depth. If the resulting texture looks inside out, you can use negative scales. Explore the other options, but it isn't necessary to change them, as the default works well. When you are satisfied, click "OK". You can now export the file as a .dds. Make sure the file is named like this: if the diffuse texture you used is called "HubbleFoil.dds", your new file should be named "HubbleFoil_norm.dds"
I'm afraid this isn't a very good tutorial, especially for someone reading who has never used GIMP before, which I don't know if you have or not. I may try to make a video tutorial.