Re: [pygame] GLSL Texturing example ? (and ctypes...?)

[Alex Holkner <aholkner@xxxxxxxxxxxxxx>]

JoN wrote:

> Sorry I should have clarified.
>
> I got that demo working fine, but then tried to modify it to do texturing and
> didn't get very far.
> What I am having problems with is the operations to set the active texture.
> I've been using some NeHe demo code to bind 2D textures just fine and have been
> happily texturing quads using python opengl.
>
> However, I am new to ctypes, which does really look like the way to go.
>  
Here's a modification to the first GLSL (coloured teapot, GL 1.5/2.0) 
example.

To load the texture data (nothing GLSLy or ctypesy here): (make sure 
your texture dimensions are powers of 2)

   import pygame.image
   image = pygame.image.load('kitten.png')
   glEnable(GL_TEXTURE_2D)
   texture = glGenTextures(1)
   glBindTexture(GL_TEXTURE_2D, texture)
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
                image.get_width(), image.get_height(),
                0, GL_RGBA, GL_UNSIGNED_BYTE,
                pygame.image.tostring(image,'RGBA', True))
   glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
   glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)

Get two more functions out of libGL using ctypes:

   glGetUniformLocation = gl.glGetUniformLocation
   glUniform1i = gl.glUniform1i

Add a uniform sampler2D to the fragment shader, and make it modulate the 
colour with the texture:
   // Fragment program
   varying vec3 pos;
   uniform sampler2D texture;
   void main() {
       gl_FragColor.rgb = pos.xyz * tex2D(texture, gl_TexCoord[0].xy).rgb;
   }

The vertex program needs to pass the texture coordinates through: 
(should multiply by the texture matrix here, but we don't care about that)
   // Vertex program
   varying vec3 pos;
   void main() {
       pos = gl_Vertex.xyz;
       gl_TexCoord[0] = gl_MultiTexCoord0;
       gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
   }

Get the location of the uniform sampler2D in Python (if it's -1, you've 
done something wrong).
   texture_param = glGetUniformLocation(program, "texture");

Set the sampler to use the first texture unit (0):
   glUseProgram(program)
   glUniform1i(texture_param, 0);
   glutSolidTeapot(1.0)

One kittened teapot.

Alex.