17. Specular light example

Vertex shader:

#version 130

in vec4 s_vPosition;
in vec4 s_vNormal;

uniform mat4 mM;    // model matrix
uniform mat4 mV;    // camera view matrix
uniform mat4 mP;    // perspective matrix

uniform mat4 mRotations; // all model rotations matrix

uniform vec4 vLight; // direction of light

out vec3 fN; // output of the normal
out vec3 fL; // output of light vector
out vec3 fE; // vector between the camera and a vertex

void main () {
    
    // Rotate the normal and pass on as vec3
    fN = (mRotations*s_vNormal).xyz;
    fL = vLight.xyz;
    // vertex is relative to the camera:
    fE = (mV*mM*s_vPosition).xyz;
    
    // From local, to world, to camera, to NDCs
    gl_Position = mP*mV*mM*s_vPosition;
}

Fragment shader:

#version 130

in vec3 fN;
in vec3 fL;
in vec3 fE; // interpolated from the vertex shader

out vec4 fColor;

void main () {
    // ALWAYS normalize the vectors after interpolation:
    vec3 N = normalize(fN);
    vec3 L = normalize(fL);
    // Reverse E: becomes vector from pixel to camera:
    vec3 E = normalize(-fE);
    vec3 H = normalize( L + E ); // Create the half vector    

    float diffuse_intensity = max(dot(N, L), 0.0);
    vec4 diffuse_color = vec4( 0.5, 0.2, 0.0, 1.0 ); // dark orange
    diffuse_color = diffuse_color * diffuse_intensity;

    float shininess = 30.0;
    float specular_intensity = pow(max(dot(N, H), 0.0), shininess);
    vec4 specular_color = vec4( 0.9, 0.1, 0.1, 1.0 ); // red
    specular_color = specular_intensity * specular_color;
    //fColor = diffuse_color; // only diffuse light
    //fColor = specular_color; // only specular light

    // dark orange with bright specular red:
    fColor = diffuse_color + specular_color;
}