michael/pathfinder
michael
/
pathfinder
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

WIP Newton's method for stencil AAA

This commit is contained in:
Patrick Walton 2018-12-01 11:48:22 -08:00
parent c1407c3970
commit 79e69c6916
1 changed files with 15 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
shaders/gles2/stencil-aaa.fs.glsl
View File

@ -21,20 +21,26 @@ void main() {
vec2 from = vFrom, ctrl = vCtrl, to = vTo; vec2 from = vFrom, ctrl = vCtrl, to = vTo;
// Determine winding, and sort into a consistent order so we only need to find one root below. // Determine winding, and sort into a consistent order so we only need to find one root below.
bool winding = from.x < to.x; vec2 v0 = ctrl - from, v1 = to - ctrl;
vec2 left = winding ? from : to, right = winding ? to : from;
vec2 v0 = ctrl - left, v1 = right - ctrl;
// Shoot a vertical ray toward the curve. // Shoot a vertical ray toward the curve.
vec2 window = clamp(vec2(from.x, to.x), -0.5, 0.5); vec2 window = clamp(vec2(from.x, to.x), -0.5, 0.5);
float offset = mix(window.x, window.y, 0.5) - left.x; //float offset = mix(window.x, window.y, 0.5) - left.x;
float t = offset / (v0.x + sqrt(v1.x * offset - v0.x * (offset - v0.x))); //float t = offset / (v0.x + sqrt(v1.x * offset - v0.x * (offset - v0.x)));
float t = 0.5;
float x = mix(mix(from.x, ctrl.x, t), mix(ctrl.x, to.x, t), t);
float dX = 2.0 * mix(v0.x, v1.x, t);
t -= x / dX;
x = mix(mix(from.x, ctrl.x, t), mix(ctrl.x, to.x, t), t);
dX = 2.0 * mix(v0.x, v1.x, t);
t -= x / dX;
// Compute position and derivative to form a line approximation. // Compute position and derivative to form a line approximation.
float y = mix(mix(left.y, ctrl.y, t), mix(ctrl.y, right.y, t), t); float y = mix(mix(from.y, ctrl.y, t), mix(ctrl.y, to.y, t), t);
float d = mix(v0.y, v1.y, t) / mix(v0.x, v1.x, t); //float dYDX = mix(v0.y, v1.y, t) / mix(v0.x, v1.x, t);
float dYDX = dFdx(y);
// Look up area under that line, and scale horizontally to the window size. // Look up area under that line, and scale horizontally to the window size.
float dX = window.x - window.y; dX = (gl_FrontFacing ? 1.0 : -1.0) * (window.x - window.y);
gl_FragColor = vec4(texture2D(uAreaLUT, vec2(y + 8.0, abs(d * dX)) / 16.0).r * dX); gl_FragColor = vec4(texture2D(uAreaLUT, vec2(y + 8.0, abs(dYDX * dX)) / 16.0).r * dX);
} }