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Ray-caster: generalize depth sorting

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Switch from a hard-coded sorting network for four fragments to an
insertion sort, which should work for any number of fragments.
This commit is contained in:
Aaron Fenyes 2024-08-25 00:47:36 -07:00
parent 8798683d25
commit c18cac642b
1 changed files with 31 additions and 23 deletions
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54
app-proto/inversive-display/src/inversive.frag
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@ -137,29 +137,37 @@ void main() {
// cast rays through the spheres
vec2 depth_pairs [sphere_cnt];
taggedFrag frags [2*sphere_cnt];
for (int i = 0; i < sphere_cnt; i++) {
int frag_cnt = 0;
for (int i = 0; i < sphere_cnt; ++i) {
vec2 hit_depths = sphere_cast(sphere_list[i], dir);
frags[2*i] = sphere_shading(sphere_list[i], hit_depths[0] * dir, color_list[i], i);
frags[2*i+1] = sphere_shading(sphere_list[i], hit_depths[1] * dir, color_list[i], i);
if (!isnan(hit_depths[0])) {
frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[0] * dir, color_list[i], i);
++frag_cnt;
}
if (!isnan(hit_depths[1])) {
frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[1] * dir, color_list[i], i);
++frag_cnt;
}
}
// shade and depth-sort the impact points
taggedFrag front_hits[2] = sort(frags[0], frags[2]);
taggedFrag back_hits[2] = sort(frags[1], frags[3]);
taggedFrag middle_frags[2] = sort(front_hits[1], back_hits[0]);
// finish depth sorting
taggedFrag frags_by_depth[4];
frags_by_depth[0] = front_hits[0];
frags_by_depth[1] = middle_frags[0];
frags_by_depth[2] = middle_frags[1];
frags_by_depth[3] = back_hits[1];
// sort the fragments by depth, using an insertion sort
for (int take = 1; take < frag_cnt; ++take) {
taggedFrag pulled = frags[take];
for (int put = take; put >= 0; --put) {
if (put < 1 || frags[put-1].pt.z >= pulled.pt.z) {
frags[put] = pulled;
break;
} else {
frags[put] = frags[put-1];
}
}
}
// highlight intersections and cusps
for (int i = 3; i >= 1; --i) {
for (int i = frag_cnt-1; i >= 1; --i) {
// intersections
taggedFrag frag0 = frags_by_depth[i];
taggedFrag frag1 = frags_by_depth[i-1];
taggedFrag frag0 = frags[i];
taggedFrag frag1 = frags[i-1];
float ixn_sin = length(cross(frag0.normal, frag1.normal));
vec3 disp = frag0.pt - frag1.pt;
float ixn_dist = max(
@ -167,21 +175,21 @@ void main() {
abs(dot(frag0.normal, disp))
) / ixn_sin;
float ixn_highlight = 0.5 * 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);
frags[i].color = mix(frags[i].color, vec4(1.), ixn_highlight);
frags[i-1].color = mix(frags[i-1].color, vec4(1.), ixn_highlight);
// cusps
float cusp_cos = abs(dot(dir, frag0.normal));
float cusp_threshold = 2.*sqrt(ixn_threshold * sphere_list[frag0.id].lt.s);
float cusp_highlight = 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);
frags[i].color = mix(frags[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].pt.z < 0.) {
vec4 frag_color = frags_by_depth[i].color;
for (int i = frag_cnt-1; i >= layer_threshold; --i) {
if (frags[i].pt.z < 0.) {
vec4 frag_color = frags[i].color;
color = mix(color, frag_color.rgb, frag_color.a);
}
}