From e3df765f16fe3ac349674b953ac9ef2cada772d9 Mon Sep 17 00:00:00 2001
From: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Date: Sat, 24 Aug 2024 01:38:06 -0700
Subject: [PATCH] Ray-caster: highlight intersections and cusps
---
app-proto/inversive-display/src/main.rs | 71 ++++++++++++++++++++-----
1 file changed, 58 insertions(+), 13 deletions(-)
diff --git a/app-proto/inversive-display/src/main.rs b/app-proto/inversive-display/src/main.rs
index c19e8ab..e3e7135 100644
--- a/app-proto/inversive-display/src/main.rs
+++ b/app-proto/inversive-display/src/main.rs
@@ -72,6 +72,8 @@ fn main() {
sycamore::render(|| {
let ctrl_x = create_signal(0.0);
let ctrl_y = create_signal(0.0);
+ let radius_x = create_signal(1.0);
+ let radius_y = create_signal(1.0);
let opacity = create_signal(0.5);
let layer_threshold = create_signal(0.0);
let display = create_node_ref();
@@ -116,12 +118,14 @@ fn main() {
// controls
uniform vec2 ctrl;
+ uniform vec2 radius;
uniform float opacity;
uniform int layer_threshold;
// light and camera
const float focal_slope = 0.3;
const vec3 light_dir = normalize(vec3(2., 2., 1.));
+ const float ixn_threshold = 0.005;
// --- sRGB ---
@@ -170,13 +174,15 @@ fn main() {
// --- shading ---
struct taggedFrag {
+ int id;
vec4 color;
- float depth;
+ vec3 pt;
+ vec3 normal;
};
taggedFrag[2] sort(taggedFrag a, taggedFrag b) {
taggedFrag[2] result;
- if (a.depth < b.depth) {
+ if (a.pt.z > b.pt.z) {
result[0] = a;
result[1] = b;
} else {
@@ -186,7 +192,7 @@ fn main() {
return result;
}
- taggedFrag sphere_shading(vecInv v, vec3 pt, vec3 base_color) {
+ taggedFrag sphere_shading(vecInv v, vec3 pt, vec3 base_color, int id) {
// the expression for normal needs to be checked. it's
// supposed to give the negative gradient of the lorentz
// product between the impact point vector and the sphere
@@ -197,7 +203,7 @@ fn main() {
float incidence = dot(normal, light_dir);
float illum = mix(0.4, 1.0, max(incidence, 0.0));
- return taggedFrag(vec4(illum * base_color, opacity), -pt.z);
+ return taggedFrag(id, vec4(illum * base_color, opacity), pt, normal);
}
// --- ray-casting ---
@@ -228,23 +234,24 @@ fn main() {
vec3 dir = vec3(focal_slope * scr, -1.);
// initialize two spheres
- vecInv v0 = sphere(vec3(0.5, 0.5, -5. + ctrl.x), 1.);
- vecInv v1 = sphere(vec3(-0.5, -0.5, -5. + ctrl.y), 1.);
+ vecInv v [2];
+ v[0] = sphere(vec3(0.5, 0.5, -5. + ctrl.x), radius.x);
+ v[1] = sphere(vec3(-0.5, -0.5, -5. + ctrl.y), radius.y);
vec3 color0 = vec3(1., 0.214, 0.);
vec3 color1 = vec3(0., 0.214, 1.);
// cast rays through the spheres
- vec2 u0 = sphere_cast(v0, dir);
- vec2 u1 = sphere_cast(v1, dir);
+ vec2 u0 = sphere_cast(v[0], dir);
+ vec2 u1 = sphere_cast(v[1], dir);
// shade and depth-sort the impact points
taggedFrag front_hits[2] = sort(
- sphere_shading(v0, u0[0] * dir, color0),
- sphere_shading(v1, u1[0] * dir, color1)
+ sphere_shading(v[0], u0[0] * dir, color0, 0),
+ sphere_shading(v[1], u1[0] * dir, color1, 1)
);
taggedFrag back_hits[2] = sort(
- sphere_shading(v0, u0[1] * dir, color0),
- sphere_shading(v1, u1[1] * dir, color1)
+ sphere_shading(v[0], u0[1] * dir, color0, 0),
+ sphere_shading(v[1], u1[1] * dir, color1, 1)
);
taggedFrag middle_frags[2] = sort(front_hits[1], back_hits[0]);
@@ -255,10 +262,32 @@ fn main() {
frags_by_depth[2] = middle_frags[1];
frags_by_depth[3] = back_hits[1];
+ // highlight intersections and cusps
+ for (int i = 3; i >= 1; --i) {
+ // intersections
+ taggedFrag frag0 = frags_by_depth[i];
+ taggedFrag frag1 = frags_by_depth[i-1];
+ float ixn_sin = length(cross(frag0.normal, frag1.normal));
+ vec3 disp = frag0.pt - frag1.pt;
+ float ixn_dist = max(
+ abs(dot(frag1.normal, disp)),
+ abs(dot(frag0.normal, disp))
+ ) / ixn_sin;
+ float ixn_highlight = 1. - smoothstep(2./3.*ixn_threshold, 1.5*ixn_threshold, ixn_dist);
+ frags_by_depth[i].color = mix(frags_by_depth[i].color, vec4(1.), ixn_highlight);
+ frags_by_depth[i-1].color = mix(frags_by_depth[i-1].color, vec4(1.), ixn_highlight);
+
+ // cusps
+ float cusp_cos = abs(dot(dir, frag0.normal));
+ float cusp_threshold = 2.*sqrt(ixn_threshold * v[frag0.id].lt.s);
+ float cusp_highlight = 1. - smoothstep(2./3.*cusp_threshold, 1.5*cusp_threshold, cusp_cos);
+ frags_by_depth[i].color = mix(frags_by_depth[i].color, vec4(1.), cusp_highlight);
+ }
+
// composite the sphere fragments
vec3 color = vec3(0.);
for (int i = 3; i >= layer_threshold; --i) {
- if (frags_by_depth[i].depth > 0.) {
+ if (frags_by_depth[i].pt.z < 0.) {
vec4 frag_color = frags_by_depth[i].color;
color = mix(color, frag_color.rgb, frag_color.a);
}
@@ -288,6 +317,7 @@ fn main() {
let resolution_loc = ctx.get_uniform_location(&program, "resolution");
let shortdim_loc = ctx.get_uniform_location(&program, "shortdim");
let ctrl_loc = ctx.get_uniform_location(&program, "ctrl");
+ let radius_loc = ctx.get_uniform_location(&program, "radius");
let opacity_loc = ctx.get_uniform_location(&program, "opacity");
let layer_threshold_loc = ctx.get_uniform_location(&program, "layer_threshold");
@@ -319,6 +349,7 @@ fn main() {
// pass the control parameters
ctx.uniform2f(ctrl_loc.as_ref(), ctrl_x.get() as f32, ctrl_y.get() as f32);
+ ctx.uniform2f(radius_loc.as_ref(), radius_x.get() as f32, radius_y.get() as f32);
ctx.uniform1f(opacity_loc.as_ref(), opacity.get() as f32);
ctx.uniform1i(layer_threshold_loc.as_ref(), layer_threshold.get() as i32);
@@ -346,6 +377,20 @@ fn main() {
step=0.001,
bind:valueAsNumber=ctrl_y
)
+ input(
+ type="range",
+ min=0.5,
+ max=1.5,
+ step=0.001,
+ bind:valueAsNumber=radius_x
+ )
+ input(
+ type="range",
+ min=0.5,
+ max=1.5,
+ step=0.001,
+ bind:valueAsNumber=radius_y
+ )
input(
type="range",
max=1.0,