OpenSubdiv/examples/evalTest/shader.glsl

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//--------------------------------------------------------------
// Vertex Shader
//--------------------------------------------------------------
#ifdef VERTEX_SHADER

layout (location=0) in vec3 position;
layout (location=1) in vec3 normal;

uniform mat4 objectToClipMatrix;
uniform mat4 objectToEyeMatrix;

out vec3 vPosition;
out vec3 vNormalEye;

void main()
{
    // vertex position in object space
    vPosition = position;

    // vertex position in clip space
    gl_Position = objectToClipMatrix * vec4(position, 1);

    // surface normal in eye space
    vNormalEye = (objectToEyeMatrix * vec4(normal, 0)).xyz;
}

#endif

//--------------------------------------------------------------
// Fragment Shader
//--------------------------------------------------------------
#ifdef FRAGMENT_SHADER

layout (location=0) out vec4 FragColor;
in vec3 vNormalEye;
in vec3 vPosition;

#define NUM_LIGHTS 2

struct LightSource {
    vec4 position;
    vec4 ambient;
    vec4 diffuse;
    vec4 specular;
};

uniform LightSource lightSource[NUM_LIGHTS];

vec4
lighting(vec3 Peye, vec3 Neye)
{
    vec4 color = vec4(0);
    vec4 material = vec4(0.4, 0.4, 0.8, 1);

    for (int i = 0; i < NUM_LIGHTS; ++i) {

        vec4 Plight = lightSource[i].position;

        vec3 l = (Plight.w == 0.0)
                    ? normalize(Plight.xyz) : normalize(Plight.xyz - Peye);

        vec3 n = normalize(Neye);
        vec3 h = normalize(l + vec3(0,0,1));    // directional viewer

        float d = max(0.0, dot(n, l));
        float s = pow(max(0.0, dot(n, h)), 500.0f);

        color += lightSource[i].ambient * material
            + d * lightSource[i].diffuse * material
            + s * lightSource[i].specular;
    }

    color.a = 1;
    return color;
}

void
main()
{
    vec3 N = (gl_FrontFacing ? vNormalEye : -vNormalEye);
    FragColor = lighting(vPosition, N);
    FragColor = vec4(1,0,0,1);  
}

#endif