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Re: GLSL Coordinate Question



http://www.gamedev.net/community/forums/topic.asp?topic_id=479695 has a good post second from bottom about this sort of thing, and may be helpful.



On Feb 4, 2008, at 10:41 AM, Alex Drinkwater wrote:

This is probably more of a GLSL than specifically a
Quartz Composer question, but maybe someone can
help...

I'm new to Vertex Shaders, though I've been messing
around with Fragment shaders for a while. I think I'm
getting confused with coordinate systems and transform
matrices. My question is this:

If I have a shader that distorts the geometry of
several discrete plane meshes, is it possible to treat
them as if they share a common coordinate space?

For example, I've used an Iterator nested inside a
GLSL patch to create a number of separate GLSL Grid
instances arranged as an array of thin vertical
strips, spread over the x-axis, with gaps between
them.

I'd like to be able to bend each strip around so that
collectively, they form a sphere, made up of bands,
with gaps between them, somewhat like this screenshot
http://machinesdontcare.files.wordpress.com/2008/01/vertexnoiseedit310108_02.jpg
(but without the distortion, which I'll add later).

What I currently get, though, is a number of small
identical spheres, spread along the x-axis. I'm
assuming this is because each grid is treated as if it
has it's own coordinate system. Is there a way of
using global or world coordinates, so that their
geometries are transformed collectively, rather than
individually?

Sorry this is a really basic question, but as I said,
I'm new to Vertex Shaders.

Cheers,


alx http://machinesdontcare.wordpress.com


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References: 
 >GLSL Coordinate Question (From: Alex Drinkwater <email@hidden>)



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