1 uniform sampler2D tex;

2 uniform float aspect, scale;

3 uniform float lens_center_offset;

4 uniform vec4 dist_factors;

5

6 vec2 distort_texcoords(in vec2 tc);

7 float barrel_scale(float x, in vec4 k);

8

9 void main()

10 {

11 vec2 tc = distort_texcoords(gl_TexCoord[0].xy);

12

13 float vis = any(greaterThan(tc, vec2(1.0)) || lessThan(tc, vec2(0.0))) ? 0.0 : 1.0;

14

15 gl_FragColor.rgb = texture2D(tex, tc).rgb * vis;

16 gl_FragColor.a = 1.0;

17 }

18

19 vec2 distort_texcoords(in vec2 tc)

20 {

21 // map tc [0, 1] -> [-1, 1]

22 vec2 pt = tc * 2.0 - 1.0;

23

24 pt.x += lens_center_offset * 2.0;

25 pt.y /= aspect; // correct for aspect ratio

26

27 float rad = barrel_scale(dot(pt, pt), dist_factors);

28 pt *= rad; // scale the point by the computer distortion radius

29

30 pt /= scale;

31 pt.y *= aspect;

32 pt.x -= lens_center_offset * 2.0;

33

34 // map back to range [0, 1]

35 return pt * 0.5 + 0.5;

36 }

37

38 float barrel_scale(float rad, in vec4 k)

39 {

40 float radsq = rad * rad;

41 float radquad = radsq * radsq;

42 return k.x + k.y * radsq + k.z * radquad + k.w * radquad * radsq;

43 }