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1 uniform sampler3D volume;
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2 uniform sampler2D ray_tex;
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3
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4 struct Ray {
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5 vec3 origin, dir;
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6 };
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7
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8 struct ISect {
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9 bool hit;
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10 float t;
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11 vec3 pos;
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12 vec3 normal;
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13 };
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14
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15 vec3 ray_march(Ray ray);
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16 vec3 shade(Ray ray, ISect isect);
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17 Ray get_primary_ray();
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18
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19 void main()
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20 {
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21 Ray ray = get_primary_ray();
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22
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23 gl_FragColor = vec4(ray_march(ray), 1.0);
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24 }
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25
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26 /*vec3 sky(Ray ray)
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27 {
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28 vec3 col1 = vec3(0.75, 0.78, 0.8);
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29 vec3 col2 = vec3(0.56, 0.7, 1.0);
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30
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31 float t = max(ray.dir.y, -0.5);
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32 return mix(col1, col2, t);
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33 }*/
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34
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35 vec3 ray_march(Ray ray)
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36 {
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37 const float ray_step = 0.05;
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38 float energy = 1.0;
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39 vec3 pos = ray.origin;
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40
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41 // assuming view space
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42 while(pos.z < 1.0) {
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43 energy -= texture3D(volume, pos).x;
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44 pos += ray.dir * ray_step;
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45 }
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46
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47 return vec3(energy, energy, energy);
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48 }
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49
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50 vec3 shade(Ray ray, ISect isect)
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51 {
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52 vec3 ldir = normalize(vec3(10.0, 10.0, -10.0) - isect.pos);
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53 vec3 vdir = -ray.dir;
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54 vec3 hdir = normalize(ldir + vdir);
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55
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56 float ndotl = dot(ldir, isect.normal);
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57 float ndoth = dot(hdir, isect.normal);
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58
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59 vec3 dcol = vec3(1.0, 1.0, 1.0) * max(ndotl, 0.0);
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60 vec3 scol = vec3(0.6, 0.6, 0.6) * pow(max(ndoth, 0.0), 50.0);
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61
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62 return vec3(0.01, 0.01, 0.01) + dcol + scol;
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63 }
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64
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65 Ray get_primary_ray()
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66 {
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67 Ray ray;
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68 vec2 tc = gl_TexCoord[0].xy;
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69 ray.dir = gl_NormalMatrix * normalize(texture2D(ray_tex, tc).xyz);
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70 ray.origin = (gl_ModelViewMatrix * vec4(0.0, 0.0, 0.0, 1.0)).xyz;
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71 return ray;
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72 }
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