Hello everybody, i am experiencing a strange problem, i atta ch my simple vertex and pixel shader hoping that some shader expert will shed some light on it , excuse me but i am pretty new to shaders.

vertex shader:

#version 330

precision highp float;

uniform mat4 ViewMatrix;
uniform mat3 NormalMatrix;
uniform mat4 ModelViewMatrix;
uniform mat4 ModelViewProjectionMatrix;

in vec4 VertexPosition;
in vec3 VertexNormal;
out vec3 Normal;

void main()
{
// All vertex shaders should write the transformed homogeneous clip space
// vertex position into the gl_Position variables.

gl_Position = ModelViewProjectionMatrix * VertexPosition;

// normal

Normal = VertexNormal;

}

pixel shader :

#version 330

precision highp float;

out vec4 FragColor;

uniform vec4 WireFrameColor;

void main()
{

FragColor = WireFrameColor ;

}


The strange fact is that if in the vertex shader, i comment out the 'normal' , i don't get rendered anything.
Where am i wrong ?
Does anybody know a place to learn modern opengl shaders ?
Thanks

I don't get any error from glloginfo function, just a black screen, during the setup process i enable everything , position, color, uv , normals, then, as i have understood correctly, i can selectively using the attributes i need according to each shader.
Could it be that i pack everything in the same vertex data and the driver gets' confused' about what to render ?
I don't think so becasue i do this:

glVertexAttribPointer(VertexAttribPosition, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex3d), BUFFER_OFFSET(0));
glVertexAttribPointer(NormalAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex3d), BUFFER_OFFSET(sizeof(float) * 4));
glVertexAttribPointer(TexCoordAttribPosition , 2, GL_FLOAT, GL_FALSE, sizeof(Vertex3d), BUFFER_OFFSET(sizeof(float) * 7));
glVertexAttribPointer(ColorCoordAttribPosition, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex3d), BUFFER_OFFSET(sizeof(float) * 9));

glEnableVertexAttribArray(VertexAttribPosition);
glEnableVertexAttribArray(NormalAttribPosition);
glEnableVertexAttribArray(TexCoordAttribPosition);
glEnableVertexAttribArray(ColorCoordAttribPosition);

the spacing in the vertex data is correct.