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OpenGL Blending and Fog in OpenGL

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I just added fog to my 3d world so you couldn''t see the edge of the map far away. But I also have water, which is blended so it is translucent. But this seems to cause a problem with the fog. Instead of the water slowly blending in with the fog at a distance and and slowly becoming not-visable, it becomes very bright and I can see the edge of it. Instead of going grey like the fog, it gets white. Anyone know how to fix this so it blends into the fog the same way as a normal, not-blended polygon?

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I don''t do OpenGL either, but....

Check that fog is still enabled when drawing the transparent part of the water. You might be drawing the floor of the water area with fog, but drawing the surface of the water after fog has been disabled.

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I don''t understand all of you. why use Direct3D, why use OpenGL? Why Why!!!!
Just create an abstract rendering class with render states. Makes it easier to port to different rasterizers / OSes

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How are you doing the fog calculations - are you just using GL''s fog? If you are, then make sure you are setting the fog up with the appropriate calls, glEnable() it, then render everything in your scene. When your done, call glDisable() on it.

Try looking at the Quake(1) engine source code, and see if that gives you any help/ideas.


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Well, the fog works perfectly with the land. At a distance the fog becomes more visable and the land becomes less visable. But with water, that doesn''t happen. it gets brighter. I tried to glEnable/Disable at different parts to fix it, but that never worked. Any clues?

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In the begining of your drawGL routine enable the fog, draw whatever you want, then disable the fog, enable the blend, draw the water, disable the blend...
It should work


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I'm actually trying to figure out the same thing (getting fog to work well with transparent water). Bruno's approach works well when the fog is far off in the distance because it gets rid of that annoying bright white. However, if you want to have a very fogy scene (you can only see 10ft in front of you), then the water sticks out like a sore thumb sense no fog calculations are used on the water.

Any idea how to resolve this other complication?

Edited by - Brett Crain on January 22, 2001 3:11:21 AM

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send me a short working program (+ a description of what u wanna do) + ill tack a looksy. fog in gl is computed per vertex


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I am too having a problem with that. However, instead of trying to play around with those crappy rendering settings or whatsoever.
I''m not going for a different approach on this one. 3D Studio MAX can use this kinda cool system to create fog. First you make define a number of vertices (e.g 8 vertices to form a box) and then try to make the fog appear inside the box only.
Just a wild idea... I have my doubts on whether it works, but if it does, it would be WAY COOL.

- A.J. Oja. -
Lead Programmer/Project Leader
DiMTEX Software

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