Getting textures to always point at the screen?

OpenGL
1

Hi, is it possible to get a texture to point/face the screen at all times using a GLSL shader? Any advice on how I would go about doing this?

2

Sounds to me like you want to read up on billboarding.

Random link: http://www.lighthouse3d.com/opengl/billboarding/

3

If you want to texture small particles you may also want to take a look at point sprites.

4

thanks for the replies. I want to have the texture map use screen co-orindates. ie. the texture bill boards but not the the 3d object.

5

Then do this in the vertex shader



varying vec4 projectSpace;

void main(){

  // Calculate the output position and projection space lookup
  projectSpace = gl_ModelViewProjectionMatrix * gl_Vertex;  
  gl_Position = projectSpace;
  projectSpace.xy = (projectSpace.xy + vec2(projectSpace.w)) * 0.5;

And this in the fragment shader:


varying vec4 projectSpace;
uniform sampler2D TextureBitmap;

void main(){

  // Look texture in screen space
  vec4 tex = texture2DProj(TextureBitmap, projectSpace);

You can scale the texture coordinates in the vertex shader to suit your needs. (by default the texture will be stretched over the screen)

6

wow thanks for your help! awesome… will try it out :wink:

7

yeah that code worked really well thanks again

8

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