gistfile1.txt

/* lighting vertex shader (not quite phong)
 * http://www.lighthouse3d.com/opengl/glsl/index.php/index.php?ogldir1
 * James Stanley 2011
 */

#version 120

void main() {
    vec3 normal, lightDir;
    vec4 diffuse, ambient;
    float NdotL;

    /* first transform the normal into eye space and normalize the result */
    normal = gl_Normal;

    /* transform light position */
    vec4 lightpos = gl_LightSource[0].position;

    /* TODO: get another shader to deal with the real lighting which is
     * directional.
     */
    lightDir = normalize(vec3(gl_Vertex - lightpos));

    /* compute the cos of the angle between the normal and lights direction. 
    The light is directional so the direction is constant for every vertex.
    Since these two are normalized the cosine is the dot product. We also 
    need to clamp the result to the [0,1] range. */
    NdotL = max(dot(normal, lightDir), 0.0);

    /* compute the ambient term */
    ambient = gl_FrontMaterial.ambient * gl_LightSource[0].ambient;

    /* Compute the diffuse term */
    diffuse = gl_FrontMaterial.diffuse * gl_LightSource[0].diffuse;

    gl_FrontColor = ambient + NdotL * diffuse;

    gl_TexCoord[0] = gl_MultiTexCoord0;

    gl_Position = ftransform();
}