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, out float dbgrad);

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

8

9 void main()

10 {

11 float dbgrad;

12 vec2 tc = distort_texcoords(gl_TexCoord[0].xy, dbgrad);

13

14 gl_FragColor.rgb = texture2D(tex, tc).rgb;

15 gl_FragColor.rgb += mix(vec3(1.0, 1.0, 0.0), vec3(0.0), smoothstep(0.01, 0.05, dbgrad));

16 gl_FragColor.a = 1.0;

17 }

18

19 vec2 distort_texcoords(in vec2 tc, out float dbgrad)

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 dbgrad = length(pt) * rad;

31

32 pt.y *= aspect;

33 pt.x -= lens_center_offset * 2.0;

34

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

36 return pt * 0.5 + 0.5;

37 }

38

39 float barrel_scale(float rad, in vec4 k)

40 {

41 float radsq = rad * rad;

42 float radquad = radsq * radsq;

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

44 }