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ehsan2004

OpenGL Some questions about bump mapping

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ehsan2004    178
It seems that bump mapping techniques just deal with diffuse color and one light. 1)So if we want to use bump mapping in our game, it means that we need to disable OpenGL lighting? 2)Which technique creates better result: Parallax or normal map? 3) Do we need to still use old manners such as dot3 extension or cube map ) to implement normal map using OpenGL fixed function? If hardware supports shader, Why not implementing this feature using shader? 4) could we mimic the behavior of more than one light while using bump map? 5) Why the codes on the internet just use the diffuse part of the lighting equation? Is it really difficult to add specular while using bump map for example? 6) Any good article or sample that solves all the problems ?

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othello    100
Hi. I'll try and answer this the best I can. Please let me know if I've said something incorrect.

1. Yes. You want to do lighting in your shader programs; OpenGL lighting is per-vertex, which causes ugly artifacts.
2. Parallax and normal maps describe different effects. I would recommend using both, because you use the parallax map to displace the normal (and diffuse, specular, etc) map texture coordinates. Also, as a side note, unless you are willing to spend a lot of computing power on parallax mapping, you will probably have artifacts in your image if you implement it.
3. You should definitely use shaders.
4. In general there are two methods for rendering multiple lights. You can either draw multiple passes, one for each light, and alpha blend them together, or you can use deferred shading techniques: http://www710.univ-lyon1.fr/~jciehl/Public/educ/GAMA/2007/Deferred_Shading_Tutorial_SBGAMES2005.pdf
5. It's really easy to add specular. Just use the normal generated by the normal map.
6. Here are some good articles:
http://www.lighthouse3d.com/opengl/glsl/index.php?lights
http://en.wikipedia.org/wiki/Phong_shading
http://www710.univ-lyon1.fr/~jciehl/Public/educ/GAMA/2007/Deferred_Shading_Tutorial_SBGAMES2005.pdf
http://www.ozone3d.net/tutorials/bump_mapping.php

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V-man    813
1) There is no such thing as OpenGL lighting in GL 3.0. GL lighting is part of the fixed pipeline and it has been eliminated. You do your own lighting with shaders now.
2) Parallax is nicer. It is a small change that cost 2 extra GPU cycles in the fragment shader.
3) Not sure what you mean. Cubemaps aren't dead.
The dot3 is part of texture combiners and tex comb is old.
4) You can do multiple lights with a single shader or use multi-pass technique.
5) I'm sure you will be an expert soon and write better and more complete shaders.
6) nope

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JackTheRapper    150
Diffuse lighting is fairly straight forward to do once the bump map is in place. Highlights are view-dependent so require a bit of extra legwork (e.g. the inverse modelview for the halfway vector to perform in tangent space).

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