Cleats really hold and push their pockets (t42 feedback)

Nothing carries the load on a slope but the ribs: each belt step every
rib moves one face cell and pushes the grains in its way, the layer on
the belt is only dragged by friction that gravity beats on 45 degrees,
and heaped grains roll back. Ribs never pass through grains or into
machines; a run that can't push stalls. The foot of an uphill run
scoops the feed into pockets. Ribs drawn as rubber bars in both looks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/render/slope-belt-shader.js

@@ -51,8 +51,18 @@ const SM_SLOPE_DRAW = `
     float sd = max(ends * 1.41421356, max(-depth, depth - ${CLEAT_HEIGHT.toFixed(1)}));
     float phase = float(wallFlags & 7);
     float wave = 0.5 + 0.5 * sin((foot + w.x - local.x - phase) * 3.14159265);
-    vec3 rubber = mix(vec3(0.16,0.18,0.21), vec3(0.21,0.23,0.27), wave);
+    vec3 rubber = mix(vec3(0.20,0.22,0.25), vec3(0.25,0.27,0.31), wave);
     C = mix(C, rubber, 1.0 - smoothstep(-px, px, sd));
+    // the ribs, where the simulation has them: rubber bars standing straight out of the belt,
+    // one every ${CLEAT_SPACING} face cells, moved along by the belt's phase
+    float dirS = (wallFlags & 32) != 0 ? 1.0 : -1.0;
+    float rc = (w.x - local.x) + foot - (grade < 0.0 ? 1.0 : 0.0) - dirS * phase;
+    float off = (mod(rc + ${(CLEAT_SPACING / 2).toFixed(1)}, ${CLEAT_SPACING.toFixed(1)}) - ${(CLEAT_SPACING / 2).toFixed(1)}) * 1.41421356;
+    float ribTop = ${((2 * CLEAT_REACH + 1) * Math.SQRT1_2).toFixed(3)};
+    float rd = length(vec2(off, depth - clamp(depth, 0.0, ribTop))) - 0.5;
+    vec3 rib = mix(vec3(0.50,0.52,0.56), vec3(0.70,0.72,0.76), smoothstep(ribTop - 1.2, ribTop, depth));
+    rib *= mix(0.78, 1.0, smoothstep(-0.5, 0.2, off * -dirS * grade));
+    C = mix(C, rib, 1.0 - smoothstep(-px, px, rd));
   }
 
   // Slopes use the flat belt's band, rollers and mesh in coordinates along the run.

src/render/slope-belts.js

@@ -160,7 +160,7 @@ function slopeDetailAt(i, x, y, smooth = false) {
   slopeWallOwner = -1;
   if (!slopeBeltHalo[(y >> 2) * BW + (x >> 2)] && !cleatMask[i]) return 0;
   if (occ[i] || mach[i] || part[i]) return 0;
-  if (cleatMask[i] && PH[mat[i]] !== PH_SOLID) return 1;
+  if (cleatMask[i] && PH[mat[i]] !== PH_SOLID) { slopeWallAt(x, y, smooth); return 1; }
   if (mat[i] !== EMPTY && PH[mat[i]] !== PH_GAS) return 0;
   return slopeWallAt(x, y, smooth) >= 0 ? 2 : 0;
 }

src/render/world.js

@@ -292,9 +292,11 @@ function drawWorld() {
       const slopeDetail = slopeDetailAt(i, x, y, sm);
       if (slopeDetail) {
         const wave = slopeDetail === 2 && ((x + beltGrade(blockP[slopeWallOwner]) * y - slopePhase[slopeWallOwner]) & 3) < 2;
-        r = slopeDetail === 1 ? 100 : wave ? 51 : 43;
-        g = slopeDetail === 1 ? 104 : wave ? 55 : 47;
-        b = slopeDetail === 1 ? 112 : wave ? 63 : 55;
+        // ribs: light rubber with a pale cap; the far wall behind them: muted, corrugated rubber
+        const cap = slopeDetail === 1 && slopeWallOwner >= 0 && !cleatMask[i - W + beltGrade(blockP[slopeWallOwner])];
+        r = slopeDetail === 1 ? (cap ? 178 : 146) : wave ? 64 : 56;
+        g = slopeDetail === 1 ? (cap ? 182 : 150) : wave ? 68 : 60;
+        b = slopeDetail === 1 ? (cap ? 190 : 158) : wave ? 76 : 68;
       }
       // incandescence
       if (T > 450 && m !== EMPTY && incand) {
@@ -346,11 +348,11 @@ function drawWorld() {
             ((y - ((sb / BW) | 0) * BS + 8) << 16) | ((x - (sb % BW) * BS + 8) << 8);
           if (slopeArt) { r = fm ? COLR[fm] : 0; g = fm ? COLG[fm] : 0; b = fm ? COLB[fm] : 0; }
         }
-        if (slopeDetail === 1) cl = 4;
-        else if (slopeDetail === 2) {
+        if (slopeDetail && slopeWallOwner >= 0) {
+          // ribs and the far wall are both drawn by the wall shader, ribs from the same phase as the simulation
           const wb = slopeWallOwner;
           cl = beltGrade(blockP[wb]) < 0 ? 31 : 32;
-          tpx[row + bx] = ((128 | slopePhase[wb] | ((slopeBeltJoins[wb] & 12) << 1)) << 24) | cl |
+          tpx[row + bx] = ((128 | slopePhase[wb] | ((slopeBeltJoins[wb] & 12) << 1) | (blockV[wb] & 1 ? 32 : 0)) << 24) | cl |
             ((y - ((wb / BW) | 0) * BS + 8) << 16) | ((x - wb % BW * BS + 8) << 8);
         }
         top = cl << 24;