Hi! I''ve heard that using alpha maps is a good way to texture terrains. With alpha maps you can combine two base textures (e.g. grass and rock). Now my question: How do I use alpha maps in opengl? How can I tell OGL that I want to use an alpha map. Do you have to use the stencil buffer for rendering alpha maps? Thanks in advance LaBasX2

I do not know what you mean with alpha maps but it seems like you just want to use the alpha value to cut out shapes like stones?

Look in the red book for information and samples using alpha testing.

I think he means using an alpha map as a height field...
In any case I don''t know how either.

If I understand what you''re looking for, checkout Tex_Env_Combine. It might be what you''re looking or at least point you in the right direction. Hope this helps.

Take Care,
Nyko

Hi!

I think ''alpha map'' is a common term in the area of terrain rendering.
Modern terrain engines like Halo and Black&White are using layers to create a high-res texturemap. These layers are blended using alpha maps.

I think Tex_Env_Combine is what I''m looking for. Thanks for the hint, Nyko!

I wrote some time ago a terrain rendering program which uses alpha maps to blend the different land textures. The blending is done in software, when the program starts (why doing it in real time, when you can pre-calculate it? For details, see my page: http://arrowsoft.ifrance.com