mesh.py

# Draw the North, East, South, West labels
label = CoreLabel( text = "North", font_size = '20sp', bold = True, color = ( 1, 1, 1, 1 ) )
label.refresh( )
texture = label.texture

Mesh( vertices = ( 0,             0,                  0, 0, 1, 1, 1, 0, 1,
                   2,             0,                  0, 0, 1, 1, 1, 1, 1,
                   2,             2,                  0, 0, 1, 1, 1, 1, 0,
                   0,             2,                  0, 0, 1, 1, 1, 0, 0 ),
      indices = [ 0, 1, 2, 0, 2, 3 ],
      fmt = self.vertex_format,
      texture = texture,
      mode = "triangles" )

simple.glsl

/* simple.glsl

simple diffuse lighting based on laberts cosine law; see e.g.:
    http://en.wikipedia.org/wiki/Lambertian_reflectance
    http://en.wikipedia.org/wiki/Lambert%27s_cosine_law
*/
---VERTEX SHADER-------------------------------------------------------
#ifdef GL_ES
    precision highp float;
#endif

attribute vec3  v_pos;
attribute vec3  v_normal;
attribute vec4  v_color;
attribute vec2  v_tc0;

uniform mat4 modelview_mat;
uniform mat4 projection_mat;
uniform float Tr;

varying vec4 normal_vec;
varying vec4 vertex_pos;
varying vec4 color_vec;
varying vec2 tc0_vec;

void main (void) {
     //compute vertex position in eye_sapce and normalize normal vector
    vec4 pos = modelview_mat * vec4(v_pos,1.0);
    vertex_pos = pos;
    normal_vec = vec4(v_normal,0.0);
    color_vec  = v_color;
    tc0_vec    = v_tc0;
    gl_Position = projection_mat * pos;
}


---FRAGMENT SHADER-----------------------------------------------------
#ifdef GL_ES
    precision highp float;
#endif

varying vec4 normal_vec;
varying vec4 vertex_pos;
varying vec4 color_vec;
varying vec2 tc0_vec;

uniform sampler2D texture0;

uniform mat4 normal_mat;
uniform vec3 Kd;
uniform vec3 Ka;
uniform vec3 Ks;
uniform float Tr;
uniform float Ns;
uniform float intensity;

void main (void){
    //correct normal, and compute light vector (assume light at the eye)
    vec4 v_normal = normalize( normal_mat * normal_vec );
    vec4 v_light = normalize( vec4(0,0,0,1) - vertex_pos );
    //reflectance based on lamberts law of cosine
    
    vec3 Ia = intensity*Kd;
    vec3 Id = intensity*Ka * max(dot(v_light, v_normal), 0.0);
    vec3 Is = intensity*Ks * pow(max(dot(v_light, v_normal), 0.0), Ns); 
    //gl_FragColor = vec4(Ia + Id + Is, Tr);

    vec4 t = texture2D( texture0, tc0_vec );
    gl_FragColor = t * color_vec;
}