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Simpler compute_subdivisions

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Grant Sanderson
2024-08-01 06:32:04 -05:00
parent c6a6503544
commit a3469c236e
1 changed files with 14 additions and 26 deletions
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40
manimlib/shaders/quadratic_bezier_stroke/geom.glsl
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@ -1,12 +1,13 @@
#version 330
layout (triangles) in;
layout (triangle_strip, max_vertices = 32) out; // Related to MAX_STEPS below
layout (triangle_strip, max_vertices = 64) out; // Related to MAX_STEPS below
uniform float anti_alias_width;
uniform float flat_stroke;
uniform float pixel_size;
uniform float joint_type;
uniform float frame_scale;
in vec3 verts[3];
@ -18,6 +19,7 @@ out vec4 color;
out float uv_stroke_width;
out float uv_anti_alias_width;
out float signed_dist_to_curve;
out float flag;
// Codes for joint types
const int NO_JOINT = 0;
@ -28,8 +30,10 @@ const int MITER_JOINT = 3;
// When the cosine of the angle between
// two vectors is larger than this, we
// consider them aligned
const float COS_THRESHOLD = 0.999;
const int MAX_STEPS = 16;
const float COS_THRESHOLD = 0.99;
// Used to determine how many lines to break the curve into
const float POLYLINE_FACTOR = 20;
const int MAX_STEPS = 32;
vec3 unit_normal = vec3(0.0, 0.0, 1.0);
@ -57,34 +61,17 @@ vec3 point_on_curve(float t){
vec3 tangent_on_curve(float t){
return 2 * (verts[1] + -verts[0]) + 2 * (verts[0] - 2 * verts[1] + verts[2]) * t;
}
void map_to_basic(out float x0, out float x2, out float scale_factor){
/* Find the coordinates and scale factor such that the bezier curve
defined by verts[] is congruent to a section of the parabola y = x^2
between x0 and x2, with scale_factor
*/
return 2 * (verts[1] - verts[0]) + 2 * (verts[0] - 2 * verts[1] + verts[2]) * t;
}
void compute_subdivision(out int n_steps, out float subdivision[MAX_STEPS]){
/*
Based on https://raphlinus.github.io/graphics/curves/2019/12/23/flatten-quadbez.html
*/
float x0;
float x2;
float scale_factor;
map_to_basic(x0, x2, scale_factor);
if (normalized_joint_product(v_joint_product[1]).w > COS_THRESHOLD){
// Linear
n_steps = 2;
}else{
n_steps = MAX_STEPS; // TODO
}
// Crude estimate for the number of polyline segments to use, based
// on the area spanned by the control points
float area = 0.5 * length(v_joint_product[1].xzy);
int count = 2 + int(round(POLYLINE_FACTOR * sqrt(area) / frame_scale));
n_steps = min(count, MAX_STEPS);
for(int i = 0; i < MAX_STEPS; i++){
if (i >= n_steps) break;
subdivision[i] = float(i) / (n_steps - 1);
@ -176,6 +163,7 @@ void emit_point_with_width(
}
void main() {
flag = 0.0;
// Curves are marked as ended when the handle after
// the first anchor is set equal to that anchor
if (verts[0] == verts[1]) return;