//
// Fragment shader for simplified uberlight model
//
// Author: Randi Rost
//         based on a RenderMan shader by Larry Gritz
//
// Copyright (c) 2003-2006: 3Dlabs, Inc.
//
// See 3Dlabs-License.txt for license information
//

uniform vec3  SurfaceColor;

// Light parameters
uniform vec3  LightColor;
uniform vec3  LightWeights;

// Surface parameters
uniform vec3  SurfaceWeights;
uniform float SurfaceRoughness;
uniform bool  AmbientClamping;

// Super ellipse shaping parameters
uniform bool  BarnShaping;
uniform float SeWidth;
uniform float SeHeight;
uniform float SeWidthEdge;
uniform float SeHeightEdge;
uniform float SeRoundness;

// Distance shaping parameters
uniform float DsNear;
uniform float DsFar;
uniform float DsNearEdge;
uniform float DsFarEdge;

varying vec3 LCpos;           // Vertex position in light coordinates  
varying vec3 LCnorm;          // Normal in light coordinates
varying vec3 LCcamera;        // Camera position in light coordinates


float superEllipseShape(vec3 pos) 
{
   if (!BarnShaping)
       return 1.0;
   else
   {
       // Project the point onto the z = 1.0 plane
      vec2 ppos   = pos.xy / pos.z;
      vec2 abspos = abs(ppos);
      
      float w = SeWidth;
      float W = SeWidth + SeWidthEdge;
      float h = SeHeight;
      float H = SeHeight + SeHeightEdge;
      
      float exp1 = 2.0 / SeRoundness;
      float exp2 = -SeRoundness / 2.0;
      
      float inner = w * h * pow(pow(h * abspos.x, exp1) +
                                pow(w * abspos.y, exp1), exp2);
      float outer = W * H * pow(pow(H * abspos.x, exp1) +
                                pow(W * abspos.y, exp1), exp2);
                                
      return 1.0 - smoothstep(inner, outer, 1.0);      
   }
}

float distanceShape(vec3 pos)
{
   float depth;
   
   depth = abs(pos.z);
   
   float dist = smoothstep(DsNear - DsNearEdge, DsNear, depth) *
                (1.0 - smoothstep(DsFar, DsFar + DsFarEdge, depth));
   return dist;
}

void main()
{
      vec3 tmpLightColor = LightColor;
        
      vec3 N = normalize(LCnorm);
      vec3 L = -normalize(LCpos);
      vec3 V = normalize(LCcamera-LCpos);
      vec3 H = normalize(L + V);
            
      vec3 tmpColor = tmpLightColor;
      
      float attenuation = 1.0;
      attenuation  *= superEllipseShape(LCpos);
      attenuation  *= distanceShape(LCpos);
      
      float ndotl   = dot(N, L);
      float ndoth   = dot(N, H);
      
      vec3 litResult;
      litResult[0]  = AmbientClamping ? max(ndotl, 0.0) : 1.0;
      litResult[1]  = max(ndotl, 0.0);
      litResult[2]  = litResult[1] * max(ndoth, 0.0) * SurfaceRoughness;
      litResult    *= SurfaceWeights * LightWeights;
      
      vec3 ambient  = tmpLightColor * SurfaceColor * litResult[0];
      vec3 diffuse  = tmpColor * SurfaceColor * litResult[1];
      vec3 specular = tmpColor * litResult[2];
      gl_FragColor  = vec4(attenuation * 
                          (ambient + diffuse + specular), 1.0);
}