GL Tools / Texture projection Matrices

franz's picture

Hi, i would like to arbitrarily project a texture on a surface, according to the camera view, so that the texture stays aligned to the camera (or any fixed point). Sounds a bit complicated to explain, so i've included a picture that shows the desired effect. This is based on an interesting link: http://www.opengl.org/resources/code/samples/mjktips/projtex/index.html

however, i'm too lost to produce interesting results.

I guess this should have something to do with the GL Load Matrix patch, but it is really under-documented. I've also tryied, unsuccessfully, to fiddle with a GLSL shader, where you can declare and multiply projection matrices....

Maybe someone here will just see what i mean, and show me the way (or the link ... ?) Thanks in advance for any hint.

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projtex2.gif
projtex2.gif19.92 KB

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yanomano's picture
Texture projection

Hi franz, it seems you are talking about "camera mapping" or "projection mapping" : This is also called sometimes "stained glass shadows" ex : in After Effects you put a textured layer between a light and the geometry and the layer project his shadow that is colored by the color of each pixel of the texture. (So finally you have a projected image)

This is a french tuto for a GLSL shader not a problem for you i think ;)

Texture mapping Ozone3D

Also very interested to do this but was not able to have this shader work...

dwskau's picture
Re: GL Tools / Texture projection Matrices

It's funny that this is coming up because I was just wishing I could do this earlier this week. I also had no idea where to start... The reason I was trying to do this is to be able to create a "shadow" of an object on a ground plane. I don't care about the object casting shadows on itself, only on a ground plane and this would allow me to do that.

gtoledo3's picture
Re: GL Tools / Texture projection Matrices

Hmm, this is one of those really inspiring chains of thought. This WOULD be quite interesting... it's one of those things that it almost seems like I have been on the tip of before but never thought too much about it to actually purposely implement.... (going to noodle around now...)