Hello,
I am a beginner in GLSL and a lot of the tutorials are now outdated which are making my life hell. I am attempting to add a simple Lambert light to my textured cube I have in a VBO. Inside this VBO I store the texture coords, vertices, indices, and normals. Everything shows up well enough on the screen, but now I want to put these normals to use with lighting. The old way seemed to use these methods in GLSL (normal = gl_NormalMatrix * gl_Normal;) however, these functions are now deprecated as I understand. Currently the cube I am rendering is too dark in some areas while rotating the cube. Does anyone think they understand the problem going on here is? I can post more code from my OpenGL app if required, here are the pics and the GLSL code.

Pictures of Cube Rotating

Vertex Shader.
#version 330

uniform mat4 viewMatrix, projectionMatrix, modelMatrix;

in vec4 in_Position;
in vec3 in_Normal;
in vec2 in_UV;

out vec2 vfTexcood;
out vec3 vfLightDirection;
out vec3 vfNormal;

void main()
{
gl_Position = (projectionMatrix * viewMatrix * modelMatrix) * in_Position;
vfTexcood = in_UV;
vec3 fvLightPosition = vec3(-100.0f, 100.0f, -100.0f);

vec4 objectPosition = modelMatrix * in_Position;
vfLightDirection = ( modelMatrix * vec4(fvLightPosition, 1)).xyz - objectPosition.xyz;

vfNormal = in_Normal;
}

Fragment Shader


#version 330

uniform sampler2D textureMap;
uniform sampler2D bumpMap;

in vec2 vfTexcood;
in vec3 vfLightDirection;
in vec3 vfNormal;

out vec4 out_Color;


void main()
{
float facingRatio = dot(normalize(vfNormal), normalize(vfLightDirection));

vec4 myColor = vec4(0.5f, 0.4f, 0.7f, 1.0f);

out_Color = texture2D( textureMap, vfTexcood) * facingRatio * myColor;
}


You multiply the light by the modelview matrix (so the normal is relative to the viewer) but you dont do that with the normal (it is in world space).

I understand, but how do you do this in GLSL? I have tried this..


vfNormal = in_Normal * mat3(modelMatrix);

but, I think the problem is that I am casting it down to mat3 and is messing it up. Do my normals need to be vec4 datatypes?

Also, what is the gl_NormalMatrix and gl_Normal anyway? I think it would help if I understood what data are in these.

Heres an explanation of normal matrix:

http://www.lighthouse3d.com/tutorials/glsl-tutorial/the-normal-matrix/

If I remember correctly the normal matrix is the same as the model matrix, except if you do non-uniform scaling, then it has to do some correction or the normal will be incorrect. But you can review the link to be sure.

I think for vfNormal it should be "mat3(modelMatrix) * in_Normal", not the reverse like you have it.

vfNormal = mat3(modelMatrix)*in_Normal;

just like your other calls. The vector is always on the right side.


gl_NormalMatrix and gl_Normal anyway? ------gl_Normal is just the input. So it is the raw data untransformed that you sent with your VBO. gl_NormalMatrix is basically the same as the modelview matrix.

Thank you all for your help and guidance. I have got it working! Now for my next step : a phong bumpmap shader.