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 0.2f
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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 |
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19 | struct fragment
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20 | {
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21 | // normalized screen position
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22 | float4 pos: WPOS;
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23 | float4 texCoord: TEXCOORD0;
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24 | float3 view: COLOR0;
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25 | };
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26 |
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27 |
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28 | struct pixel
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29 | {
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30 | float4 illum_col: COLOR0;
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31 | };
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32 |
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33 |
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34 | float2 reflect(float2 pt, float2 n)
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35 | {
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36 | // distance to plane
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37 | float d = dot(n, pt);
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38 | // reflect around plane
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39 | float2 rpt = pt - d * 2.0f * n;
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40 | return rpt;
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41 | }
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42 |
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43 |
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44 |
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45 | /** The ssao shader returning the an intensity value between 0 and 1
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46 | */
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47 | float ssao(fragment IN,
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48 | uniform sampler2D positions,
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49 | uniform sampler2D noiseTexture,
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50 | uniform float2 samples[NUM_SAMPLES],
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51 | uniform float3 currentNormal,
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52 | uniform float3 currentViewDir,
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53 | uniform float noiseMultiplier,
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54 | uniform float4 centerPosition
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55 | )
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56 | {
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57 | // the w coordinate from the persp. projection
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58 | float w = centerPosition.w;
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59 |
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60 | // Check in a circular area around the current position.
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61 | // Shoot vectors to the positions there, and check the angle to these positions.
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62 | // Summing up these angles gives an estimation of the occlusion at the current position.
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63 |
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64 | float total_ao = 0.0;
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65 |
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66 | for (int i = 0; i < NUM_SAMPLES; ++ i)
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67 | {
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68 | float2 offset = samples[i];
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69 |
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70 | ////////////////////
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71 | // add random noise: r stores costheta, g stores sintheta
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72 |
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73 | //float2 mynoise = tex2D(noiseTexture, IN.texCoord.xy * noiseMultiplier).xy * 2.0f - 1.0f;
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74 | float2 mynoise = tex2D(noiseTexture, IN.texCoord.xy * noiseMultiplier).xy;
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75 |
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76 | float2 offsetTransformed = reflect(offset, mynoise);
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77 |
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78 | // weight with projected coordinate to reach similar kernel size for near and far
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79 | float2 texcoord = IN.texCoord.xy + offsetTransformed * AREA_SIZE * w;
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80 |
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81 | // sample downsampled texture in order to speed up texture accesses
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82 | float3 sample_position = tex2Dlod(positions, float4(texcoord, 0, 1)).xyz;
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83 | //float3 sample_position = tex2D(positions, texcoord).xyz;
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84 |
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85 | float3 vector_to_sample = sample_position - centerPosition.xyz;
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86 | const float length_to_sample = length(vector_to_sample);
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87 |
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88 | float3 direction_to_sample = vector_to_sample / length_to_sample;
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89 |
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90 | // Angle between current normal and direction to sample controls AO intensity.
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91 | const float cos_angle = max(dot(direction_to_sample, currentNormal), 0.0f);
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92 |
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93 | // distance between current position and sample position controls AO intensity.
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94 | const float distance_intensity =
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95 | (SAMPLE_INTENSITY * DISTANCE_SCALE) / (DISTANCE_SCALE + length_to_sample * length_to_sample);
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96 |
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97 | // if surface normal perpenticular to view dir, some samples probably count less
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98 | // => compensate for this
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99 | const float view_correction = 1.0f + VIEW_CORRECTION_SCALE * (1.0f - dot(currentViewDir, currentNormal));
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100 |
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101 | total_ao += cos_angle * distance_intensity * view_correction;
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102 | }
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103 |
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104 | return max(0.0f, 1.0f - total_ao);
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105 | }
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106 |
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107 |
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108 | /** The mrt shader for screen space ambient occlusion
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109 | */
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110 | pixel main(fragment IN,
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111 | uniform sampler2D colors,
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112 | uniform sampler2D positions,
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113 | uniform sampler2D normals,
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114 | uniform sampler2D noiseTexture,
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115 | uniform float2 samples[NUM_SAMPLES],
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116 | uniform float noiseMultiplier,
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117 | uniform sampler2D oldTex,
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118 | const uniform float4x4 oldModelViewProj,
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119 | uniform float maxDepth,
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120 | uniform float expFactor
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121 | )
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122 | {
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123 | pixel OUT;
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124 |
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125 | float4 norm = tex2D(normals, IN.texCoord.xy);
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126 |
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127 | // the ambient term
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128 | const float amb = norm.w;
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129 |
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130 | // expand normal
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131 | float3 normal = normalize(norm.xyz);
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132 | /// the current view direction
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133 | float3 viewDir = normalize(IN.view * 2.0f - float3(1.0f));
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134 |
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135 | // the current world position
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136 | const float4 centerPosition = tex2D(positions, IN.texCoord.xy);
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137 |
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138 | // the current color
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139 | const float4 currentCol = tex2D(colors, IN.texCoord.xy);
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140 | const float currentDepth = currentCol.w;
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141 |
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142 | const float ao = ssao(IN, positions, noiseTexture, samples, normal, viewDir, noiseMultiplier, centerPosition);
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143 |
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144 |
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145 | /////////////////
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146 | //-- compute temporally smoothing
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147 |
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148 | float4 realPos = centerPosition * maxDepth;
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149 | realPos.w = 1.0f;
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150 |
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151 | // reproject
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152 | float4 oldPos = mul(oldModelViewProj, realPos);
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153 |
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154 | const float newDepth = oldPos.z / oldPos.w;
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155 |
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156 | float2 tex = (oldPos.xy / oldPos.w) * 0.5f + 0.5f;
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157 | float4 oldCol = tex2D(oldTex, tex);
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158 |
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159 | const float oldDepth = oldCol.w;
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160 | const float depthDif = 1.0f - newDepth / oldDepth;
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161 |
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162 |
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163 | if ((tex.x >= 0.0f) && (tex.x < 1.0f) &&
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164 | (tex.y >= 0.0f) && (tex.y < 1.0f) &&
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165 | (abs(depthDif) < 1e-3f))
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166 | {
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167 | OUT.illum_col.x = ao * expFactor + oldCol.x * (1.0f - expFactor);
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168 | }
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169 | else
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170 | {
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171 | OUT.illum_col.x = ao;
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172 | }
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173 |
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174 | OUT.illum_col.w = currentDepth;
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175 |
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176 | return OUT;
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177 | }
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178 |
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179 |
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180 |
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181 | pixel combine(fragment IN,
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182 | uniform sampler2D colors,
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183 | uniform sampler2D ssaoTex)
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184 | {
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185 | pixel OUT;
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186 |
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187 | float4 col = tex2D(colors, IN.texCoord.xy);
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188 | float4 ao = tex2D(ssaoTex, IN.texCoord.xy);
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189 |
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190 | OUT.illum_col = col * ao.x;
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191 |
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192 | return OUT;
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193 | } |
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