slang-shaders/include/img/curvature.h

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2020-04-29 13:37:24 +10:00
#ifndef CURV
#define CURV
// A collection of 2D curvature/warp functions
// torridgristle
vec2 tg_warp(vec2 texCoord){
vec2 Distortion = vec2(warpX, warpY) * 15.;
vec2 curvedCoords = texCoord * 2.0 - 1.0;
float curvedCoordsDistance = sqrt(curvedCoords.x*curvedCoords.x+curvedCoords.y*curvedCoords.y);
curvedCoords = curvedCoords / curvedCoordsDistance;
curvedCoords = curvedCoords * (1.0-pow(vec2(1.0-(curvedCoordsDistance/1.4142135623730950488016887242097)),(1.0/(1.0+Distortion*0.2))));
curvedCoords = curvedCoords / (1.0-pow(vec2(0.29289321881345247559915563789515),(1.0/(vec2(1.0)+Distortion*0.2))));
curvedCoords = curvedCoords * 0.5 + 0.5;
return curvedCoords;
}
// lottes
// Distortion of scanlines, and end of screen alpha.
vec2 tl_warp(vec2 pos)
{
pos = pos*2.0-1.0;
pos *= vec2(1.0 + (pos.y*pos.y)*warpX, 1.0 + (pos.x*pos.x)*warpY);
return pos*0.5 + 0.5;
}
// cgwg's geom
// license: GPLv2
const float d = 1.5;
const vec2 sinangle = vec2(1.0);
const vec2 cosangle = vec2(1.0);
const vec2 aspect = vec2(1.0, 0.75);
float R = max(warpX, warpY);
#define FIX(c) max(abs(c), 1e-5);
float intersect(vec2 xy)
{
float A = dot(xy,xy) + d*d;
float B = 2.0*(R*(dot(xy,sinangle) - d*cosangle.x*cosangle.y) - d*d);
float C = d*d + 2.0*R*d*cosangle.x*cosangle.y;
return (-B-sqrt(B*B - 4.0*A*C))/(2.0*A);
}
vec2 fwtrans(vec2 uv)
{
float r = FIX(sqrt(dot(uv,uv)));
uv *= sin(r/R)/r;
float x = 1.0-cos(r/R);
float D = d/R + x*cosangle.x*cosangle.y+dot(uv,sinangle);
return d*(uv*cosangle-x*sinangle)/D;
}
vec3 maxscale()
{
vec2 c = bkwtrans(-R * sinangle / (1.0 + R/d*cosangle.x*cosangle.y));
vec2 a = vec2(0.5,0.5)*aspect;
vec2 lo = vec2(fwtrans(vec2(-a.x, c.y)).x,
fwtrans(vec2( c.x, -a.y)).y)/aspect;
vec2 hi = vec2(fwtrans(vec2(+a.x, c.y)).x,
fwtrans(vec2( c.x, +a.y)).y)/aspect;
return vec3((hi+lo)*aspect*0.5,max(hi.x-lo.x,hi.y-lo.y));
}
vec2 bkwtrans(vec2 xy)
{
float c = intersect(xy);
vec2 point = (vec2(c, c)*xy - vec2(-R, -R)*sinangle) / vec2(R, R);
vec2 poc = point/cosangle;
vec2 tang = sinangle/cosangle;
float A = dot(tang, tang) + 1.0;
float B = -2.0*dot(poc, tang);
float C = dot(poc, poc) - 1.0;
float a = (-B + sqrt(B*B - 4.0*A*C)) / (2.0*A);
vec2 uv = (point - a*sinangle) / cosangle;
float r = FIX(R*acos(a));
return uv*r/sin(r/R);
}
vec2 cgwg_warp(vec2 coord)
{
vec3 stretch = max_scale();
coord = (coord - vec2(0.5, 0.5))*aspect*stretch.z + stretch.xy;
return (bkwtrans(coord) /
vec2(1.0, 1.0)/aspect + vec2(0.5, 0.5));
}
float corner(vec2 coord)
{
coord = (coord - vec2(0.5)) + vec2(0.5, 0.5);
coord = min(coord, vec2(1.0) - coord) * aspect;
vec2 cdist = vec2(cornersize);
coord = (cdist - min(coord, cdist));
float dist = sqrt(dot(coord, coord));
return clamp((cdist.x - dist)*cornersmooth, 0.0, 1.0);
}
#endif