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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 // cast rays through the spheres
vec2 depth_pairs [sphere_cnt]; vec2 depth_pairs [sphere_cnt];
taggedFrag frags [2*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); 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); if (!isnan(hit_depths[0])) {
frags[2*i+1] = sphere_shading(sphere_list[i], hit_depths[1] * dir, color_list[i], i); 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 // sort the fragments by depth, using an insertion sort
taggedFrag front_hits[2] = sort(frags[0], frags[2]); for (int take = 1; take < frag_cnt; ++take) {
taggedFrag back_hits[2] = sort(frags[1], frags[3]); taggedFrag pulled = frags[take];
taggedFrag middle_frags[2] = sort(front_hits[1], back_hits[0]); for (int put = take; put >= 0; --put) {
if (put < 1 || frags[put-1].pt.z >= pulled.pt.z) {
// finish depth sorting frags[put] = pulled;
taggedFrag frags_by_depth[4]; break;
frags_by_depth[0] = front_hits[0]; } else {
frags_by_depth[1] = middle_frags[0]; frags[put] = frags[put-1];
frags_by_depth[2] = middle_frags[1]; }
frags_by_depth[3] = back_hits[1]; }
}
// highlight intersections and cusps // highlight intersections and cusps
for (int i = 3; i >= 1; --i) { for (int i = frag_cnt-1; i >= 1; --i) {
// intersections // intersections
taggedFrag frag0 = frags_by_depth[i]; taggedFrag frag0 = frags[i];
taggedFrag frag1 = frags_by_depth[i-1]; taggedFrag frag1 = frags[i-1];
float ixn_sin = length(cross(frag0.normal, frag1.normal)); float ixn_sin = length(cross(frag0.normal, frag1.normal));
vec3 disp = frag0.pt - frag1.pt; vec3 disp = frag0.pt - frag1.pt;
float ixn_dist = max( float ixn_dist = max(
@ -167,21 +175,21 @@ void main() {
abs(dot(frag0.normal, disp)) abs(dot(frag0.normal, disp))
) / ixn_sin; ) / ixn_sin;
float ixn_highlight = 0.5 * highlight * (1. - smoothstep(2./3.*ixn_threshold, 1.5*ixn_threshold, ixn_dist)); 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[i].color = mix(frags[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-1].color = mix(frags[i-1].color, vec4(1.), ixn_highlight);
// cusps // cusps
float cusp_cos = abs(dot(dir, frag0.normal)); float cusp_cos = abs(dot(dir, frag0.normal));
float cusp_threshold = 2.*sqrt(ixn_threshold * sphere_list[frag0.id].lt.s); 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)); 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 // composite the sphere fragments
vec3 color = vec3(0.); vec3 color = vec3(0.);
for (int i = 3; i >= layer_threshold; --i) { for (int i = frag_cnt-1; i >= layer_threshold; --i) {
if (frags_by_depth[i].pt.z < 0.) { if (frags[i].pt.z < 0.) {
vec4 frag_color = frags_by_depth[i].color; vec4 frag_color = frags[i].color;
color = mix(color, frag_color.rgb, frag_color.a); color = mix(color, frag_color.rgb, frag_color.a);
} }
} }