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glowing ray effect (Read 1008 times)
julapy
glowing ray effect
May 11th, 2008, 5:08am  
hi guys,

im making a glowing ray effect, so far the way ive approached this was to create a number of cylinders which fan out from the center of a sphere.

http://www.julapy.com/processing/rays.mp4

the left side of the sphere blends correctly while the right doesn't seem to blend at all.  tried using a quad instead of a cylinder and got the same result.
also tried disabling depth test, gl.glDisable( GL.GL_DEPTH_TEST ), but no change.

does anyone have an idea of how to fix this?

also, if anyone has any other ways of creating this effect, be great to hear ur approach.
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ascorbin
Re: glowing ray effect
Reply #1 - May 11th, 2008, 10:59am  
Hi julapy

You surely have seen this:

http://codeanticode.wordpress.com/2008/05/04/gltexture-renamed-to-glgraphics/

There you can combine the Offscreen example with the BloomEffect example and everything you draw is nicely bloomed

Test your Blendmodes:
http://processing.org/discourse/yabb_beta/YaBB.cgi?board=OpenGL;action=display;num=1207671111

greetings ascorbin
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JohnG
Re: glowing ray effect
Reply #2 - May 11th, 2008, 11:17am  
Your problem is your draw order.

There is one easy way to work around it, as well as disabling the depth test, disable writing depth information with gl.glDepthMask(0); (or possibly 1.. can't remember which is "on" and which is "off") for your cylinders.
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julapy
Re: glowing ray effect
Reply #3 - May 11th, 2008, 4:10pm  
thx guys, disabling the depth mask did the trick.
gl.glDepthMask( false );

JohnG, i had a quick google and ur absolutely right, when drawing transparent or opaque objects its best to draw them back to front. im guessing this would involve some kind of z-sorting. wonder if opengl can do this before rendering to screen...

ascorbin, yeh been following that thread and GLSL is very high on the todo list... just have to get the fundamentals down first.

thx again guys.
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