Easy lambertian shading

lambertian.frag

#version 100

precision mediump float;

varying vec3 normal;
varying vec2 texCoord;

uniform sampler2D texture;

const vec3 light = vec3(0.21821789023, 0.43643578047, 0.87287156094);

void main()
{
	float costheta = dot(normal, light);
	vec3 col = max(costheta, 0.0) * texture2D(texture, texCoord).rgb;
	gl_FragColor = vec4(col, 1.0);
}