зеркало из https://github.com/mozilla/gecko-dev.git
94 строки
3.5 KiB
GLSL
94 строки
3.5 KiB
GLSL
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifdef WR_FRAGMENT_SHADER
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// One iteration of Newton's method on the 2D equation of an ellipse:
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//
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// E(x, y) = x^2/a^2 + y^2/b^2 - 1
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//
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// The Jacobian of this equation is:
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//
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// J(E(x, y)) = [ 2*x/a^2 2*y/b^2 ]
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//
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// We approximate the distance with:
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//
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// E(x, y) / ||J(E(x, y))||
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//
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// See G. Taubin, "Distance Approximations for Rasterizing Implicit
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// Curves", section 3.
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float distance_to_ellipse(vec2 p, vec2 radii, float aa_range) {
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float dist;
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if (any(lessThanEqual(radii, vec2(0.0)))) {
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dist = length(p);
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} else {
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vec2 invRadiiSq = 1.0 / (radii * radii);
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float g = dot(p * p * invRadiiSq, vec2(1.0)) - 1.0;
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vec2 dG = 2.0 * p * invRadiiSq;
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dist = g * inversesqrt(dot(dG, dG));
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}
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return clamp(dist, -aa_range, aa_range);
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}
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float clip_against_ellipse_if_needed(
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vec2 pos,
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float current_distance,
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vec4 ellipse_center_radius,
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vec2 sign_modifier,
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float aa_range
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) {
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if (!all(lessThan(sign_modifier * pos, sign_modifier * ellipse_center_radius.xy))) {
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return current_distance;
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}
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float distance = distance_to_ellipse(pos - ellipse_center_radius.xy,
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ellipse_center_radius.zw,
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aa_range);
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return max(distance, current_distance);
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}
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float rounded_rect(vec2 pos,
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vec4 clip_center_radius_tl,
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vec4 clip_center_radius_tr,
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vec4 clip_center_radius_br,
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vec4 clip_center_radius_bl,
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float aa_range) {
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// Start with a negative value (means "inside") for all fragments that are not
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// in a corner. If the fragment is in a corner, one of the clip_against_ellipse_if_needed
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// calls below will update it.
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float current_distance = -aa_range;
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// Clip against each ellipse.
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current_distance = clip_against_ellipse_if_needed(pos,
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current_distance,
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clip_center_radius_tl,
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vec2(1.0),
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aa_range);
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current_distance = clip_against_ellipse_if_needed(pos,
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current_distance,
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clip_center_radius_tr,
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vec2(-1.0, 1.0),
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aa_range);
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current_distance = clip_against_ellipse_if_needed(pos,
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current_distance,
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clip_center_radius_br,
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vec2(-1.0),
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aa_range);
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current_distance = clip_against_ellipse_if_needed(pos,
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current_distance,
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clip_center_radius_bl,
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vec2(1.0, -1.0),
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aa_range);
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// Apply AA
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// See comment in ps_border_corner about the choice of constants.
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return distance_aa(aa_range, current_distance);
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}
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#endif
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