//
//   Copyright 2013 Pixar
//
//   Licensed under the Apache License, Version 2.0 (the "Apache License")
//   with the following modification; you may not use this file except in
//   compliance with the Apache License and the following modification to it:
//   Section 6. Trademarks. is deleted and replaced with:
//
//   6. Trademarks. This License does not grant permission to use the trade
//      names, trademarks, service marks, or product names of the Licensor
//      and its affiliates, except as required to comply with Section 4(c) of
//      the License and to reproduce the content of the NOTICE file.
//
//   You may obtain a copy of the Apache License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the Apache License with the above modification is
//   distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
//   KIND, either express or implied. See the Apache License for the specific
//   language governing permissions and limitations under the Apache License.
//

//#version 330

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

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

out vec3 vPosition;
out vec3 vNormal;
out vec4 vColor;

void main()
{
    vPosition = position;
    vNormal = normal;
    vColor = vec4(1, 1, 1, 1);
}

#endif

//--------------------------------------------------------------
// Geometry Shader
//--------------------------------------------------------------
#ifdef GEOMETRY_SHADER

#ifdef PRIM_QUAD

layout(lines_adjacency) in;

#ifdef GEOMETRY_OUT_FILL
layout(triangle_strip, max_vertices = 4) out;
#endif

#ifdef GEOMETRY_OUT_LINE
layout(line_strip, max_vertices = 5) out;
#endif

in vec3 vPosition[4];
in vec3 vNormal[4];

#else // PRIM_TRI

layout(triangles) in;

#ifdef GEOMETRY_OUT_FILL
layout(triangle_strip, max_vertices = 3) out;
#endif

#ifdef GEOMETRY_OUT_LINE
layout(line_strip, max_vertices = 4) out;
#endif

in vec3 vPosition[3];
in vec3 vNormal[3];

#endif // PRIM_TRI/QUAD


uniform mat4 objectToClipMatrix;
uniform mat4 objectToEyeMatrix;

flat out vec3 gFacetNormal;
out vec3 Peye;
out vec3 Neye;
out vec4 Cout;

void emit(int index)
{
    Peye = vPosition[index];
    gl_Position = objectToClipMatrix * vec4(vPosition[index], 1);
    Neye = (objectToEyeMatrix * vec4(vNormal[index], 0)).xyz;
    EmitVertex();
}

void main()
{
    gl_PrimitiveID = gl_PrimitiveIDIn;
    
#ifdef PRIM_QUAD
#ifdef GEOMETRY_OUT_FILL
    vec3 A = vPosition[0] - vPosition[1];
    vec3 B = vPosition[3] - vPosition[1];
    vec3 C = vPosition[2] - vPosition[1];

    gFacetNormal = (objectToEyeMatrix*vec4(normalize(cross(B, A)), 0)).xyz;
    emit(0);
    emit(1);
    emit(3);
//    gFacetNormal = (objectToEyeMatrix*vec4(normalize(cross(C, B)), 0)).xyz;
    emit(2);
#else  // GEOMETRY_OUT_LINE
    emit(0);
    emit(1);
    emit(2);
    emit(3);
    emit(0);
#endif
#endif // PRIM_QUAD

#ifdef PRIM_TRI
    vec3 A = vPosition[1] - vPosition[0];
    vec3 B = vPosition[2] - vPosition[0];
    gFacetNormal = (objectToEyeMatrix*vec4(normalize(cross(B, A)), 0)).xyz;

    emit(0);
    emit(1);
    emit(2);
#ifdef GEOMETRY_OUT_LINE
    emit(0);
#endif //GEOMETRY_OUT_LINE
#endif // PRIM_TRI

    EndPrimitive();
}

#endif

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

layout (location=0) out vec4 FragColor;
flat in vec3 gFacetNormal;
in vec3 Neye;
in vec3 Peye;
in vec4 Cout;

#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;
}

#ifdef GEOMETRY_OUT_LINE
uniform vec4 fragColor;
void
main()
{
    FragColor = fragColor;
}

#else

void
main()
{
    vec3 N = (gl_FrontFacing ? gFacetNormal : -gFacetNormal);
    FragColor = lighting(Peye, N);
}
#endif // GEOMETRY_OUT_LINE

#endif