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examples/gkurve: border rendering, non-linear field

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Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
This commit is contained in:
Stephen Gutekanst 2022-05-20 12:26:43 -07:00
parent 58709070dd
commit eae2a090c6
3 changed files with 34 additions and 15 deletions
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32
examples/gkurve/frag.wgsl
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@ -6,7 +6,7 @@ struct FragUniform {
@stage(fragment) fn main(
@location(0) uv: vec2<f32>,
@location(1) bary: vec3<f32>,
@interpolate(linear) @location(1) bary: vec3<f32>,
@interpolate(flat) @location(2) triangle_index: u32,
) -> @location(0) vec4<f32> {
// Example 1: Visualize barycentric coordinates:
@ -15,7 +15,7 @@ struct FragUniform {
// return vec4<f32>(0.0, bary.y, 0.0, 1.0); // bottom-right of triangle
// return vec4<f32>(0.0, bary.z, 0.0, 1.0); // top of triangle
// Example 2: Render gkurves
// Example 2: Render gkurve primitives
var inversion = -1.0;
if(ubos[triangle_index].type_ == 1u) {
// Solid triangle
@ -24,13 +24,31 @@ struct FragUniform {
// Concave (inverted quadratic bezier curve)
inversion = -1.0;
} else {
// Convex (inverted quadratic bezier curve)
// Convex (quadratic bezier curve)
inversion = 1.0;
}
var dist = (-(pow(bary.z, 4.0) - bary.y * bary.x)) * inversion;
if (dist < 0.0) {
discard;
}
// Gradients
let px = dpdx(bary.xy);
let py = dpdy(bary.xy);
// Chain rule
let fx = (2.0 * bary.x) * px.x - px.y;
let fy = (2.0 * bary.x) * py.x - py.y;
// Signed distance
var dist = (bary.x * bary.x - bary.y) / sqrt(fx * fx + fy * fy);
// var dist = bary.z*bary.z - bary.y;
dist *= inversion;
dist /= 128.0;
dist /= 1.75;
// Border rendering.
if (dist > 0.0 && dist <= 0.1) { return vec4<f32>(1.0, 0.0, 0.0, 1.0); }
if (dist > 0.2 && dist <= 0.3) { return vec4<f32>(0.0, 0.0, 1.0, 1.0); }
// Fill color
if (dist < 0.0) { discard; }
return vec4<f32>(0.0, 1.0, 0.0, 1.0);
}