1 | ////////////////////
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2 | // Screen Spaced Ambient Occlusion shader
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3 | // based on shader of Alexander Kusternig
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4 |
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5 | #define NUM_SAMPLES 10
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6 | //#define NUM_SAMPLES 16
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7 |
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8 | // rule of thumb: approx 1 / NUM_SAMPLES
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9 | //#define SAMPLE_INTENSITY 0.15f
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10 | #define SAMPLE_INTENSITY 0.22f
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11 |
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12 | #define AREA_SIZE 7e-1f
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13 | //#define AREA_SIZE 3e-1f
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14 | #define VIEW_CORRECTION_SCALE 0.3f
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15 | //#define VIEW_CORRECTION_SCALE 0.5f
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16 | #define DISTANCE_SCALE 1e-6f
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17 |
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18 | #define ILLUM_INTENSITY 5e-1f;
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19 |
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20 |
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21 | struct fragment
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22 | {
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23 | // normalized screen position
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24 | float4 pos: WPOS;
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25 | float4 texCoord: TEXCOORD0;
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26 | float3 view: COLOR0;
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27 | };
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28 |
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29 |
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30 |
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31 | struct pixel2
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32 | {
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33 | float4 ssao_col: COLOR0;
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34 | float4 illum_col: COLOR1;
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35 | };
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36 |
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37 |
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38 | struct pixel
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39 | {
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40 | float4 illum_col: COLOR0;
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41 | };
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42 |
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43 |
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44 | float2 reflect(float2 pt, float2 n)
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45 | {
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46 | // distance to plane
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47 | float d = dot(n, pt);
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48 | // reflect around plane
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49 | float2 rpt = pt - d * 2.0f * n;
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50 | return rpt;
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51 | }
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52 |
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53 | /** Computes diffuse reflections + ambient occlusion
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54 | */
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55 | float4 globIllum(fragment IN,
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56 | uniform sampler2D colors,
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57 | uniform sampler2D positions,
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58 | uniform sampler2D noiseTexture,
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59 | uniform float2 samples[NUM_SAMPLES],
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60 | uniform float3 currentNormal,
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61 | uniform float3 currentViewDir,
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62 | uniform float noiseMultiplier,
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63 | uniform float4 centerPosition
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64 | )
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65 | {
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66 | // the w coordinate from the persp. projection
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67 | float w = centerPosition.w;
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68 |
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69 | // Check in a circular area around the current position.
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70 | // Shoot vectors to the positions there, and check the angle to these positions.
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71 | // Summing up these angles gives an estimation of the occlusion at the current position.
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72 |
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73 | // ao is in stored in the w component
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74 | float4 total_color = float4(0, 0, 0, 1);
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75 |
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76 |
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77 | ////////////
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78 | //-- the main sampling loop
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79 |
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80 | for (int i = 0; i < NUM_SAMPLES; i ++)
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81 | {
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82 | float2 offset = samples[i];
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83 |
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84 | //sample noisetex; r stores costheta, g stores sintheta
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85 | float2 mynoise = tex2D(noiseTexture, IN.texCoord.xy * noiseMultiplier).xy;
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86 |
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87 | // rotation
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88 | float2 offsetTransformed = reflect(offset, mynoise);
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89 |
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90 | // weight with projected coordinate to reach similar kernel size for near and far
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91 | float2 texcoord = IN.texCoord.xy + offsetTransformed * AREA_SIZE * w;
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92 |
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93 | // use lower lod level to improve cache coherence
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94 | float3 sample_position = tex2Dlod(positions, float4(texcoord, 0, 1)).xyz;
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95 | float3 sample_color = tex2Dlod(colors, float4(texcoord, 0, 2)).xyz;
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96 |
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97 | float3 vector_to_sample = sample_position - centerPosition.xyz;
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98 | const float length_to_sample = length(vector_to_sample);
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99 |
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100 | float3 direction_to_sample = vector_to_sample / length_to_sample;
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101 |
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102 | // Angle between current normal and direction to sample controls AO intensity.
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103 | float cos_angle = max(dot(direction_to_sample, currentNormal), 0);
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104 |
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105 | // distance between current position and sample position controls AO intensity.
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106 | const float distance_intensity =
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107 | (SAMPLE_INTENSITY * DISTANCE_SCALE) / (DISTANCE_SCALE + length_to_sample * length_to_sample);
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108 |
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109 | // if normal perpenticular to view dir, only half of the samples count
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110 | const float view_correction = 1.0f + VIEW_CORRECTION_SCALE * (1.0f - dot(currentViewDir, currentNormal));
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111 |
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112 | total_color.w -= cos_angle * distance_intensity * view_correction;
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113 |
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114 | total_color.xyz += cos_angle * distance_intensity * view_correction * sample_color * ILLUM_INTENSITY;
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115 | }
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116 |
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117 | return saturate(total_color);
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118 | }
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119 |
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120 |
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121 | /** The mrt shader for screen space ambient occlusion + indirect illumination
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122 | */
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123 | pixel2 main(fragment IN,
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124 | uniform sampler2D colors,
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125 | uniform sampler2D positions,
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126 | uniform sampler2D normals,
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127 | uniform sampler2D noiseTexture,
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128 | uniform float2 samples[NUM_SAMPLES],
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129 | uniform float noiseMultiplier,
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130 | uniform sampler2D oldSsaoTex,
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131 | uniform sampler2D oldIllumTex,
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132 | const uniform float4x4 oldModelViewProj,
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133 | uniform float maxDepth,
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134 | uniform float expFactor
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135 | )
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136 | {
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137 | pixel2 OUT;
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138 |
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139 | float4 norm = tex2D(normals, IN.texCoord.xy);
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140 |
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141 | // the ambient term
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142 | const float amb = norm.w;
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143 |
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144 | // expand normal
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145 | float3 normal = normalize(norm.xyz);
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146 | /// the current view direction
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147 | float3 viewDir = normalize(IN.view * 2.0f - float3(1.0f));
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148 |
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149 | // the current world position
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150 | const float4 centerPosition = tex2D(positions, IN.texCoord.xy);
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151 |
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152 | // the current color
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153 | const float4 currentCol = tex2Dlod(colors, float4(IN.texCoord.xy, 0, 0));
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154 | // the current depth is stored in the w component
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155 | const float currentDepth = currentCol.w;
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156 |
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157 | float4 new_color = globIllum(IN, colors, positions, noiseTexture,
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158 | samples, normal, viewDir, noiseMultiplier, centerPosition);
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159 |
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160 |
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161 | /////////////////
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162 | //-- compute temporally smoothing
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163 |
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164 | float4 realPos = centerPosition * maxDepth;
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165 | realPos.w = 1.0f;
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166 |
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167 | float4 oldPos = mul(oldModelViewProj, realPos);
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168 |
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169 | const float newDepth = oldPos.z / oldPos.w;
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170 |
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171 | float2 tex = (oldPos.xy / oldPos.w) * 0.5f + 0.5f;
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172 |
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173 | float4 oldSsao = tex2D(oldSsaoTex, tex);
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174 | float4 oldIllum = tex2D(oldIllumTex, tex);
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175 |
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176 | const float oldDepth = oldSsao.w;
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177 | const float depthDif = 1.0f - newDepth / oldDepth;
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178 |
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179 |
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180 | if ((tex.x >= 0.0f) && (tex.x < 1.0f) &&
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181 | (tex.y >= 0.0f) && (tex.y < 1.0f) &&
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182 | (abs(depthDif) < 1e-3f))
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183 | {
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184 | OUT.ssao_col.x = new_color.w * expFactor + oldSsao.x * (1.0f - expFactor);
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185 | OUT.illum_col = new_color * expFactor + oldIllum * (1.0f - expFactor);
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186 | }
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187 | else
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188 | {
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189 | OUT.ssao_col.x = new_color.w;
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190 | OUT.illum_col = new_color;
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191 | }
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192 |
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193 | OUT.ssao_col.w = currentDepth;
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194 |
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195 | return OUT;
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196 | }
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197 |
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198 |
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199 | pixel combine(fragment IN,
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200 | uniform sampler2D colors,
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201 | uniform sampler2D ssaoTex,
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202 | uniform sampler2D illumTex
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203 | )
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204 | {
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205 | pixel OUT;
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206 |
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207 | float4 col = tex2D(colors, IN.texCoord.xy);
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208 | float ao = tex2D(ssaoTex, IN.texCoord.xy).x;
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209 | float4 illum = tex2D(illumTex, IN.texCoord.xy);
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210 |
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211 | OUT.illum_col = (col + illum) * ao;
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212 |
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213 | return OUT;
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214 | }
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