radiance: margin inside the glass rim; haloed corona sparks and glints (oversized soft-falloff points)

src/scripts/orb.js

@@ -98,7 +98,8 @@ float lifeAlpha(float x) {
 float layerR(uint idx) {
   float k = h01(idx * 8u + 5u);
   float u = h01(idx * 8u + 4u);
-  return k < 0.5 ? mix(0.94, 1.0, u) : mix(0.4, 0.94, u);
+  // both stay clear of the glass at r = 1, leaving a margin around the rim
+  return k < 0.5 ? mix(0.86, 0.925, u) : mix(0.4, 0.85, u);
 }
 // A drifting ridge field: density peaks along thin curved sheets, which cut the sphere as ribbons.
 float density(vec3 dir, float t) {
@@ -372,7 +373,7 @@ void main() {
   }
   float r = length(pos);
   vec3 n = pos / max(r, 1e-4);
-  float surf = step(0.9, rt);
+  float surf = step(0.855, rt);
 
   // the cursor: the 2D fluid under the particle's screen position, pushed into 3D
   vec3 bp = bodyToView(pos);
@@ -403,7 +404,7 @@ void main() {
   n = pos / max(r, 1e-4);
   vel -= n * max(dot(vel, n), 0.0) * smoothstep(rt - 0.05, rt + 0.01, r);
   r = mix(r, rt, 1.0 - exp(-uDt * 1.6));
-  pos = n * min(r, 0.985);
+  pos = n * min(r, 0.93);
 
   stir = max(stir * exp(-uDt * 1.2), clamp(fm * front * 1.5, 0.0, 1.5));
   oPos = vec4(pos, stir);
@@ -425,6 +426,7 @@ uniform float uR;       // css px
 uniform float uDpr;
 out vec4 vColor;
 out float vGlow;
+out float vCore;
 
 void main() {
   uint idx = uint(gl_VertexID);
@@ -458,17 +460,17 @@ void main() {
     size = mix(1.5 + r.y * 1.5 + n * 1.3, 2.8 + r.w * 2.4, spark);
     float tw = 0.5 + 0.5 * sin(t * (1.2 + r.x * 2.5) + r.w * 40.0);
     col.a *= mix(1.0, mix(0.4, 1.0, tw), spark);
-    vGlow = spark;
+    vGlow = spark * 0.5;
     // the far side reads dimmer through the glass, and so do particles hanging deep in the volume
     // (it also thins the crowd that edge-on particles would form along the limb)
     col.a *= mix(0.2, 1.0, smoothstep(-0.2, 0.6, bp.z));
-    col.a *= mix(0.65, 1.0, step(0.9, rt));
+    col.a *= mix(0.65, 1.0, step(0.855, rt));
     col.a *= lifeAlpha(lt);
     // stirred particles heat up: brighter, hotter, a little bigger
     col.rgb = mix(col.rgb, vec3(1.0, 0.8, 0.55), clamp(stir * 0.3, 0.0, 0.4));
     col.a = min(1.0, col.a * (1.0 + stir * 0.5));
-    size *= 1.0 + stir * 0.8;
+    size *= 1.0 + stir * 0.5;
-    vGlow = max(vGlow, clamp(stir * 0.8, 0.0, 1.0));
+    vGlow = max(vGlow, clamp(stir * 0.2, 0.0, 0.25));
   } else {
     P p = corona(idx);
     vec2 disp = s0.xy;
@@ -491,7 +493,10 @@ void main() {
 
   vec2 px = uCenter + vec2(vp.x, -vp.y) * uR;
   gl_Position = vec4(px.x / uView.x * 2.0 - 1.0, 1.0 - px.y / uView.y * 2.0, 0.0, 1.0);
-  gl_PointSize = size * sc * uDpr * persp;
+  // glowing points are drawn larger so the halo has room around the core
+  float glowScale = 1.0 + vGlow * 2.4;
+  gl_PointSize = size * sc * uDpr * persp * glowScale;
+  vCore = 1.0 / glowScale;
   vColor = col;
 }
 `;
@@ -499,12 +504,12 @@ void main() {
 const FRAG_PARTICLES = `${HEAD}
 in vec4 vColor;
 in float vGlow;
+in float vCore;     // the core's share of the point's width; the rest is room for the halo
 out vec4 o;
 void main() {
-  vec2 c = gl_PointCoord - 0.5;
+  float rr = length(gl_PointCoord - 0.5) * 2.0;   // 0 at the centre, 1 at the edge of the point
-  float r = length(c);
+  float core = 1.0 - smoothstep(0.36 * vCore, vCore, rr);
-  float core = smoothstep(0.5, 0.18, r);
+  float halo = vGlow * pow(max(1.0 - rr, 0.0), 2.2) * 0.55;
-  float halo = vGlow * smoothstep(0.5, 0.0, r) * 0.55;
   float a = vColor.a * clamp(core + halo, 0.0, 1.0);
   if (a < 0.01) discard;
   o = vec4(vColor.rgb * a, a);