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nuclear@13
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1 uniform sampler2D tex;
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2 uniform float aspect, scale;
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3 uniform float lens_center_offset;
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4 uniform vec4 dist_factors;
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5
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6 vec2 distort_texcoords(in vec2 tc, out float dbgrad);
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7 float barrel_scale(float x, in vec4 k);
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8
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9 void main()
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10 {
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11 float dbgrad;
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12 vec2 tc = distort_texcoords(gl_TexCoord[0].xy, dbgrad);
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13
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14 gl_FragColor.rgb = texture2D(tex, tc).rgb;
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15 gl_FragColor.rgb += mix(vec3(1.0, 1.0, 0.0), vec3(0.0), smoothstep(0.01, 0.05, dbgrad));
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16 gl_FragColor.a = 1.0;
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17 }
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18
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19 vec2 distort_texcoords(in vec2 tc, out float dbgrad)
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20 {
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21 // map tc [0, 1] -> [-1, 1]
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22 vec2 pt = tc * 2.0 - 1.0;
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23
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24 pt.x += lens_center_offset * 2.0;
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25 pt.y /= aspect; // correct for aspect ratio
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26
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27 float rad = barrel_scale(dot(pt, pt), dist_factors);
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28 pt *= rad; // scale the point by the computer distortion radius
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29
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30 dbgrad = length(pt) * rad;
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31
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32 pt.y *= aspect;
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33 pt.x -= lens_center_offset * 2.0;
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34
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35 // map back to range [0, 1]
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36 return pt * 0.5 + 0.5;
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37 }
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38
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39 float barrel_scale(float rad, in vec4 k)
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40 {
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41 float radsq = rad * rad;
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42 float radquad = radsq * radsq;
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43 return k.x + k.y * radsq + k.z * radquad + k.w * radquad * radsq;
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44 }
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