Practical Algorithms for 3D Computer Graphics, 2nd Edition

7.3. The GL sha d in g language 283

// Vertex Shader - for traditional image mapping

#version 330 core

layout(location = 0) in vec3 Vertex;

layout(location = 1) in vec3 Normal;

layout(location = 2) in vec2 Texture;

uniform mat4 MVP;

uniform mat4 MV;

uniform mat4 NM;

uniform vec3 LightPos;

out float Diffuse; // diffuse light intensity

out vec2 TexCoord; // texture coordinate (u,v)

void main(){

gl_Position = MVP * vec4(Vertex,1); // buit in variable

vec3 PP = MV * vec4(Vertex,1); // vertex position world coodinates

vec3 PN = normalize(NM * Normal);// normal vector

// light direction vector

vec3 LV = normalize(LightPos-PV);

Diffuse = max(dot(LV, PN), 0.0); // diffuse ...