I am attempting to get some simple diffuse lighting to work in GLSL. I have a cube that is being passed in as an array of points and I'm calculating the face normals inside my geometry shader (because I intend to deform the mesh at run-time so I'll need the new face normals.)
My problem is that the diffuse value is changing as I move the camera around the world. so the shading on a face of my cube changes as the camera moves. I have not been able to figure out what I am missing that is causing this. My shaders are as follows:
Vertex:
#version 330 core
layout(location = 0) in vec3 vertexPosition_modelspace;
uniform mat4 MVP;
void main(){
gl_Position = MVP * vec4(vertexPosition_modelspace,1);
}
Geometry:
#version 330
precision highp float;
layout (triangles) in;
layout (triangle_strip) out;
layout (max_vertices = 3) out;
out vec3 normal;
uniform mat4 MVP;
uniform mat4 MV;
void main(void)
{
for (int i = 0; i < gl_in.length(); i++) {
gl_Position = gl_in[i].gl_Position;
vec3 U = gl_in[1].gl_Position.xyz - gl_in[0].gl_Position.xyz;
vec3 V = gl_in[2].gl_Position.xyz - gl_in[0].gl_Position.xyz;
normal.x = (U.y * V.z) - (U.z * V.y);
normal.y = (U.z * V.x) - (U.x * V.z);
normal.z = (U.x * V.y) - (U.y * V.x);
normal = normalize(transpose(inverse(MV)) * vec4(normal,1)).xyz;
EmitVertex();
}
EndPrimitive();
}
Fragment:
#version 330 core
in vec3 normal;
out vec4 out_color;
const vec3 lightDir = vec3(-1,-1,1);
uniform mat4 MV;
void main()
{
vec3 nlightDir = normalize(vec4(lightDir,1)).xyz;
float diffuse = clamp(dot(nlightDir,normal),0,1);
out_color = vec4(diffuse*vec3(0,1,0),1.0);
}
Thanks