How do I manage to draw helicopter rotor blades which fade because of the high speed ? I think the effect is called motion blur but I don''t know how to handle that in openGL. Thanks !

Motion blur is usually created with the accumulation buffer but no card has hw support for it so you can not do it in realtime. Some 3dfx card has a T-buffer that perhaps can be used.

Is it necessary for your purposes to render the individual blades? Often times I see this effect achieved by placing a flat disc on top of the helicopter, onto which an animated texture is placed which mimicks the whirling blades.

mmmh this is interesting since I don''t care to draw the single blades...
I''ll try to do that

I helped a friend overcome this issue a long time ago. Here''s what we did...

1. Hit http://www.3dcafe.com and view the free models, download a decent looking helicopter model, there are several. Mostly worry about the quality of the rotors.

2. Load the model into MAX / Maya / MilkShape / Rhino / TrueSpace / etc...

3. Delete all unwanted parts of the model but the primary and tail rotors blades. Make sure the materials are up to your standards or fix them.

4. Orient the view so you are directly above the primary blades, then animate 24 frames of simple rotation, 15 degrees each frame should be acceptable. Render this, check the animation.

5. Repeat for the tail rotor.

6. Apply these animated textures to your model, which indeed should be a simple flat cylinder.

I''ll try to locate out project files if I can. Good luck.

I did rotor blades in RedStorm''s Force 21. They were a simple quad with an alpha blended texture. No animation, but if the texture is good it''ll fool everyone. Of course you could rotate the quad too for added realism.

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excuse me if i''m dumb but ... a quad is quad, and the rotor revolution describe a circle so ... teach me please ...

The texture that is rendered on the quad should have an alpha channel for the parts of the texture outside the circle created by the blades. This is a very low cost solution to your problem. A thin cylinder with a texture is more polys than a quad and the texture would have to be similar anyway.

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that means that alpha channel is used to make trasparent the part of the texture outside the rotor blade area ?

Exactly, we used the .tga file format for the texture.

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Visit Particle Stream Studios - Home of Europa, Tachyon and winSkin