source: trunk/tutorial/04_texture.lolfx @ 2190

Last change on this file since 2190 was 2190, checked in by sam, 7 years ago

tutorial: add fancy dots to line segment ends.

File size: 1.9 KB
Line 
1[vert.glsl]
2
3#version 120
4
5attribute vec2 in_Position;
6
7varying vec4 pass_Position;
8
9void main(void)
10{
11    pass_Position = vec4(0.5 * in_Position + 0.5, 0.0, 1.0);
12    gl_Position = vec4(in_Position, 0.5, 1.0);
13}
14
15[frag.glsl]
16
17#version 120
18
19uniform sampler2D u_Texture;
20
21varying vec4 pass_Position;
22
23float segdist(vec2 p1, vec2 p2, vec2 a)
24{
25    float d = max(1e-10, dot(p2 - p1, p2 - p1));
26    float t = clamp(dot(a - p1, p2 - p1) / d, 0.0, 1.0);
27    return distance(a, mix(p1, p2, t));
28}
29
30void main(void)
31{
32    float width = 800.0;
33    float height = 600.0;
34    float line_width = 1.8;
35    float dot_size = 2.0;
36    vec4 delta = vec4(1.0 / 128, 0.0,
37                      2.0 / 128, 0.0);
38
39    vec2 p = pass_Position.xy;
40    vec2 tc = vec2(floor(p.x * 128.0) / 128.0, p.y);
41    float t = p.x * 128.0 - floor(p.x * 128.0);
42    vec4 c;
43    c[0] = texture2D(u_Texture, tc - delta.xy).x;
44    c[1] = texture2D(u_Texture, tc).x;
45    c[2] = texture2D(u_Texture, tc + delta.xy).x;
46    c[3] = texture2D(u_Texture, tc + delta.zw).x;
47
48    vec2 p0 = vec2((tc.x - delta.x) * width, c[0] * height);
49    vec2 p1 = vec2((tc.x          ) * width, c[1] * height);
50    vec2 p2 = vec2((tc.x + delta.x) * width, c[2] * height);
51    vec2 p3 = vec2((tc.x + delta.z) * width, c[3] * height);
52    vec2 a = vec2(p.x * width, p.y * height);
53
54    /* Compute distance to segments */
55    float d =        segdist(p0, p1, a);
56          d = min(d, segdist(p1, p2, a));
57          d = min(d, segdist(p2, p3, a));
58
59    /* Compute distance to dots */
60    d = min(d, length(a - p0) - dot_size);
61    d = min(d, length(a - p1) - dot_size);
62    d = min(d, length(a - p2) - dot_size);
63    d = min(d, length(a - p3) - dot_size);
64
65    /* Add line width */
66    float lum = clamp(line_width - d, 0.0, 1.0);
67
68    /* Compensate for sRGB */
69    lum = pow(1.0 - lum, 1.0 / 2.4);
70
71    /* Choose some funny colours */
72    gl_FragColor = vec4(mix(p.x, 1.0, lum), lum, lum, 1.0);
73}
74
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