Question

I have been reading a pdf file on OpenGL lighting.

It says for the Gouraud Shading:

• Gouraud shading
– Set vertex normals
– Calculate colors at vertices
– Interpolate colors across polygon
• Must calculate vertex normals!
• Must normalize vertex normals to unit length!

So that’s what I did.
Here is my Vertex and Fragment Shader file

V_Shader:

#version 330

layout(location = 0) in vec3 in_Position; //declare position
layout(location = 1) in vec3 in_Color;

// mvpmatrix is the result of multiplying the model, view, and projection matrices */
uniform mat4 MVP_matrix;
vec3 ambient;

out vec3 ex_Color;

void main(void) {

   // Multiply the MVP_ matrix by the vertex to obtain our final vertex position (mvp was created in *.cpp)
   gl_Position = MVP_matrix * vec4(in_Position, 1.0);
   ambient = vec3(0.0f,0.0f,1.0f);
   ex_Color = ambient * normalize(in_Position) ; //anti ex_Color=in_Color;
}

F_shader:

#version 330

in vec3 ex_Color;
out vec4 gl_FragColor;

void main(void) {
   gl_FragColor = vec4(ex_Color,1.0);
}

The interpolation is taken care by the fragment shader right?

so here is my sphere (it is low polygon btw):

Is this the standard way of implementing Gouraud Shading?
(my sphere has a center of (0,0,0))
Thanks for your patience

Answer 1

ex_Color = ambient * normalize(in_Position) ; //anti ex_Color=in_Color;

Allow me to quote myself, “It certainly doesn’t qualify as ‘lighting’.” That didn’t stop being true between the first time you asked this question and now.

This is not lighting. This is just normalizing the model-space position and multiplying it by the ambient color. Even if we assume that the model-space position is centered at zero and represents a point on the sphere, multiplying a light by a normal is meaningless. It is not lighting.

If you want to learn how lighting works, read this. Or this.