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/* 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;
uniform mat4 modelview_mat;
uniform mat4 projection_mat;
varying vec4 normal_vec;
varying vec4 vertex_pos;
void main (void) {
//compute vertex position in eye_space and normalize normal vector
vec4 pos = modelview_mat * vec4(v_pos,1.0);
vertex_pos = pos;
normal_vec = vec4(v_normal,0.0);
gl_Position = projection_mat * pos;
}
---FRAGMENT SHADER-----------------------------------------------------
#ifdef GL_ES
precision highp float;
#endif
varying vec4 normal_vec;
varying vec4 vertex_pos;
uniform mat4 normal_mat;
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
float theta = clamp(dot(v_normal, v_light), 0.0, 1.0);
gl_FragColor = vec4(theta, theta, theta, 1.0);
}
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