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airseb

about how to program "radial blur"

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Hi ! i have read this :http: //nehe.gamedev.net/data/lessons/lesson.asp?lesson=36 i''m not sure of having understood this tutorial : it displays an object, render it to a texture and then reduce the size of the texture by keeping the luminance of the object and it redisplay the object ? that''s all ? have i forgotten something ? but what is the light which come from the object, except the one of glLightfv (that we can see by downloading the code) ? lightings are they obligatory ? thanks.

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Truth is that there is no light that is the radial blur. All he did was draw translucent versions of the spiraled object scaled quite a few times. That creates the effect. The same sort of effect can be seen in my demo: http://members.rogers.com/ramrajb/Downloads/Portrait.ZIP

If you have the fog coordinate extension look into the sun. All it is, is just scaled particles that begin small and expand to infinite scale.

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thanks, now i would like to know how by reducing the texture, it produces light ?
can you help me ?

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This might make it clearer:



The image starts small, with high alpha so it looks bright at the center. As we make the image larger, we reduce the alpha. Do this quite a few times and we have the same image but with a blur that seems to radiate out from the center - its all repetitions on the same image scaled outward. We associate it with light because it looks like there is a light source behind it.

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It doesn’t produce light. When you overlap blended the overlapped colors "add". Like explained above the more overlapped the brighter and more white of a image is created.

In the radial blur it renders the image to a texture and then while blending it resizes and puts the texture across the screen. So you have 25 images overlapping. Where the image overlaps the most will be the brightest. The smallest version of the texture will typically overlap the majority of the applied resized texture. The larger and larger the texture is applied the less it will overlap and it will therefore create a fade to the background color.

I hope I didn’t confuse you more.

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thanks guys !
but now i would like to know how the radial blur effect can be above the object ? it''s thanks to glViewport ? if yes, how ?
thanks !

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I believe that in the tutorial it is - this is because you are drawing the textured quads infront of the scene. In my candle and island they arnt. In those instances they are particles so i can make them behave any way i want to. This lets my keep it 2d on the candle and not infront of the object or lets me make the blur fan out like lines accross my island scene.

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