1 | [vert.glsl] |
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2 | |
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3 | #version 120 |
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4 | |
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5 | attribute vec2 in_Position; |
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6 | |
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7 | varying vec4 pass_Position; |
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8 | |
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9 | void main(void) |
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10 | { |
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11 | pass_Position = vec4(0.5 * in_Position + 0.5, 0.0, 1.0); |
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12 | gl_Position = vec4(in_Position, 0.5, 1.0); |
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13 | } |
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14 | |
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15 | [frag.glsl] |
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16 | |
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17 | #version 120 |
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18 | |
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19 | uniform sampler2D u_Texture; |
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20 | |
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21 | varying vec4 pass_Position; |
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22 | |
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23 | float segdist(vec2 p1, vec2 p2, vec2 a) |
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24 | { |
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25 | float d = max(1e-10, dot(p2 - p1, p2 - p1)); |
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26 | float t = clamp(dot(a - p1, p2 - p1) / d, 0.0, 1.0); |
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27 | return distance(a, mix(p1, p2, t)); |
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28 | } |
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29 | |
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30 | void main(void) |
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31 | { |
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32 | float width = 800.0; |
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33 | float height = 600.0; |
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34 | float texture_width = 256.0; |
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35 | float line_width = 1.2; |
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36 | float dot_size = 1.0; |
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37 | vec4 delta = vec4(1.0 / texture_width, 0.0, |
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38 | 2.0 / texture_width, 0.0); |
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39 | |
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40 | vec2 p = pass_Position.xy; |
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41 | vec2 tc = vec2(floor(p.x * texture_width) / texture_width, p.y); |
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42 | float t = p.x * texture_width - floor(p.x * texture_width); |
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43 | vec4 c; |
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44 | c[0] = texture2D(u_Texture, tc - delta.xy).x; |
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45 | c[1] = texture2D(u_Texture, tc).x; |
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46 | c[2] = texture2D(u_Texture, tc + delta.xy).x; |
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47 | c[3] = texture2D(u_Texture, tc + delta.zw).x; |
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48 | |
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49 | /* Find the 4 closest points in screen space */ |
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50 | vec2 p0 = vec2((tc.x - delta.x) * width, c[0] * height); |
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51 | vec2 p1 = vec2((tc.x ) * width, c[1] * height); |
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52 | vec2 p2 = vec2((tc.x + delta.x) * width, c[2] * height); |
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53 | vec2 p3 = vec2((tc.x + delta.z) * width, c[3] * height); |
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54 | vec2 a = vec2(p.x * width, p.y * height); |
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55 | |
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56 | /* Compute distance to segments */ |
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57 | float d = segdist(p0, p1, a); |
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58 | d = min(d, segdist(p1, p2, a)); |
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59 | d = min(d, segdist(p2, p3, a)); |
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60 | |
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61 | /* Compute distance to dots */ |
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62 | d = min(d, length(a - p0) - dot_size); |
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63 | d = min(d, length(a - p1) - dot_size); |
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64 | d = min(d, length(a - p2) - dot_size); |
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65 | d = min(d, length(a - p3) - dot_size); |
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66 | |
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67 | /* Add line width */ |
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68 | float lum = clamp(line_width - d, 0.0, 1.0); |
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69 | |
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70 | /* Compensate for sRGB */ |
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71 | lum = pow(1.0 - lum, 1.0 / 2.4); |
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72 | |
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73 | /* Choose some funny colours */ |
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74 | gl_FragColor = vec4(mix(p.x, 1.0, lum), lum, lum, 1.0); |
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75 | } |
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76 | |
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