Upload log-u8 density grids directly to GPU in reduced-motion mode

js/src/45_lod.ts

@@ -118,10 +118,14 @@ export function lodWriteGridTexture(
       }
     }
   }
+  lodUploadGridBytes(gl, tex, data, w, h, !!rgba, filter);
+}
+
+function lodUploadGridBytes(gl, tex, data, w, h, isRgba, filter) {
   gl.bindTexture(gl.TEXTURE_2D, tex);
   const align = gl.getParameter(gl.UNPACK_ALIGNMENT);
   gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1);
-  if (rgba) {
+  if (isRgba) {
     gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA8, w, h, 0, gl.RGBA, gl.UNSIGNED_BYTE, data);
   } else {
     gl.texImage2D(gl.TEXTURE_2D, 0, gl.R8, w, h, 0, gl.RED, gl.UNSIGNED_BYTE, data);
@@ -136,6 +140,12 @@ export function lodWriteGridTexture(
   gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
 }
 
+export function lodUploadWireGrid(gl, u8Wire, w, h, filter) {
+  const tex = gl.createTexture();
+  lodUploadGridBytes(gl, tex, u8Wire, w, h, false, filter);
+  return tex;
+}
+
 // Treat the color scale like exposure: brighten slowly on drill-in so a
 // smaller aggregate tile does not suddenly go hot, but recover faster when
 // the incoming tile needs more headroom to avoid clipping.
@@ -1220,14 +1230,19 @@ export function lodApplyDensityUpdate(view, g, upd, buffers) {
       }
     }
   }
-  const grid = d.enc === "log-u8"
-    ? lodDecodeLogU8(buffers[d.buf], d.max)
-    : lodCopyGrid(view._asF32(buffers[d.buf]));
-  // Mean point color plane (LOD doc §2), copied because exposure easing
-  // re-reads it on every norm step, after the wire buffer may be gone.
+  // Mean point color plane (LOD doc §2), copied because legend-hover dimming
+  // and home-restore re-uploads re-read it after the wire buffer may be gone.
   const rgba = d.rgba !== undefined ? new Uint8Array(view._asU8(buffers[d.rgba])) : null;
   const normStart = lodNormMax(g, d.max);
-  const normMax = view._prefersReducedMotion() ? d.max : normStart;
+  const reducedMotion = view._prefersReducedMotion();
+  const normMax = reducedMotion ? d.max : normStart;
+  const directWire = d.enc === "log-u8" && !rgba && reducedMotion;
+  const wire = directWire ? new Uint8Array(view._asU8(buffers[d.buf])) : null;
+  const grid = directWire
+    ? null
+    : d.enc === "log-u8"
+      ? lodDecodeLogU8(buffers[d.buf], d.max)
+      : lodCopyGrid(view._asF32(buffers[d.buf]));
   g.densityNormMax = normMax;
   g.prevDensity = g.density;
   g._densityFadeStart = view._now();
@@ -1241,12 +1256,15 @@ export function lodApplyDensityUpdate(view, g, upd, buffers) {
     // enough to points territory to be worth a round-trip at all.
     visible: upd.visible,
     grid,
+    wire,
     rgba,
     filter,
     _filterKey: replyFilterKey,
-    tex: view._uploadGrid(
-      grid, d.w, d.h, normMax, rgba, filter, view._fillOpacity(g.trace.style),
-    ),
+    tex: directWire
+      ? lodUploadWireGrid(view.gl, wire, d.w, d.h, filter)
+      : view._uploadGrid(
+        grid, d.w, d.h, normMax, rgba, filter, view._fillOpacity(g.trace.style),
+      ),
     lut: g.density.lut,
   };
   // Exact scans include a view-specific sample and replace the overlay.

js/src/54_kernel.ts

@@ -4,6 +4,7 @@ import { parseColor } from "./20_theme";
 import {
   lodAggregateStands, lodAggregateStepWindow, lodApplyDensityUpdate, lodApplyDrill,
   lodDrillServesView, lodDropDrill, lodFilterKey, lodPromoteCachedDrill, lodRememberDensity,
+  lodUploadWireGrid,
 } from "./45_lod";
 import { xyCreateRebinWorker } from "./46_worker";
 import { ChartView } from "./50_chartview";
@@ -280,10 +281,12 @@ Object.assign(ChartView.prototype, {
         const hd = g._homeDensity;
         this._applySampleRebinGrid(g, {
           ...hd,
-          tex: this._uploadGrid(
-            hd.grid, hd.w, hd.h, hd.normMax || hd.max || 1, hd.rgba, hd.filter,
-            this._fillOpacity(g.trace.style),
-          ),
+          tex: hd.grid
+            ? this._uploadGrid(
+              hd.grid, hd.w, hd.h, hd.normMax || hd.max || 1, hd.rgba, hd.filter,
+              this._fillOpacity(g.trace.style),
+            )
+            : lodUploadWireGrid(this.gl, hd.wire, hd.w, hd.h, hd.filter),
         }, false);
       }
       return;

scripts/render_smoke_nonumpy.py

@@ -790,6 +790,35 @@ def main() -> None:
         if(c>0&&Math.abs(qg[i]-c)/c>0.08)qok=0;}}
     }}
     const qwire=(qok && Math.abs(gd.density.max-qmax)<1e-9)?1:0;
+    // --- Direct-wire density (reduced motion): a count-only log-u8 reply
+    // uploads the wire bytes verbatim (grid null, normMax pinned to max) and
+    // retains a copy on density.wire so re-uploads survive without a decoded
+    // grid. Then the home-extent restore in _requestSampleRebin — the path
+    // that dereferenced the null grid — must re-upload from the wire copy.
+    const rmPrev=v._prefersReducedMotion.bind(v);
+    v._prefersReducedMotion=()=>true;
+    const rmax=9, renc=new Uint8Array(64);
+    for(let i=0;i<64;i++){{const c=(i%4===0)?9:(i%7===0?1:0);
+      renc[i]=c>0?Math.max(1,Math.min(255,Math.round(255*Math.log1p(c)/Math.log1p(rmax)))):0;}}
+    v._onKernelMsg({{type:"density_update",traces:[{{id:gd.trace.id,mode:"density",visible:12345,
+      density:{{buf:0,w:8,h:8,max:rmax,enc:"log-u8",x_range:[0,100],y_range:[0,100]}}}}]}},[renc.buffer.slice(0)]);
+    let dwire=(gd.density.grid===null && gd.density.wire instanceof Uint8Array &&
+      gd.density.wire.length===64 && gd.density.normMax===rmax &&
+      v.gl.isTexture(gd.density.tex))?1:0;
+    if(dwire){{for(let i=0;i<64;i++) if(gd.density.wire[i]!==renc[i]) dwire=0;}}
+    let drestore=0;
+    try{{
+      gd._homeDensity=gd.density;
+      v._onKernelMsg({{type:"density_update",traces:[{{id:gd.trace.id,mode:"density",visible:2345,
+        density:{{buf:0,w:8,h:8,max:rmax,enc:"log-u8",x_range:[40,60],y_range:[40,60]}}}}]}},[renc.buffer.slice(0)]);
+      const zoomed=gd.density!==gd._homeDensity;
+      if(!v.view0) v.view0={{...v.view}};
+      v._requestSampleRebin(gd, v.view0, 0);
+      drestore=(zoomed && gd.density.grid===null && gd.density.wire instanceof Uint8Array &&
+        gd.density.xRange[1]===100 && v.gl.isTexture(gd.density.tex))?1:0;
+    }}catch(e){{ drestore=0; }}
+    gd._homeDensity=null;
+    v._prefersReducedMotion=rmPrev;
     // --- Rapid zoom in/out torture (drill thrash): the marks/density alphas
     // must be CONTINUOUS across window-boundary crossings, dying-drill
     // revives, and kernel replies landing mid-transition. Runs on a virtual
@@ -1169,7 +1198,7 @@ def main() -> None:
     gMc.readPixels(Math.round(WM*0.8),Math.round(HM*0.5),1,1,gMc.RGBA,gMc.UNSIGNED_BYTE,rpx);
     const meancolor=(lpx[0]>60 && lpx[0]>lpx[2]*3 && rpx[2]>60 && rpx[2]>rpx[0]*3)?1:0;
     vMc.destroy();holderMc.remove();
-    const base=`XY_OK lit=${{lit}} total=${{w*h}} labels=${{labels}} pick=${{hits}} row=${{hasXY}} selAll=${{selAll}} selSome=${{selSome}} active=${{active}} btns=${{btns}} modebarHidden=${{modebarHiddenAtRest}} modebarTopLeft=${{modebarTopLeft}} modebarHover=${{modebarHoverReveal}} modebarNoCollapse=${{modebarNoCollapse}} modebarMenu=${{modebarMenu}} modebarDrag=${{modebarDrag}} modebarSelect=${{modebarSelect}} lassoEdit=${{lassoEdit}} modebarExport=${{modebarExport}} panToggle=${{panToggle}} zin=${{zin}} smooth=${{smooth}} labelThrottle=${{labelThrottle}} hoverSkip=${{hoverSkip}} zanch=${{zanch}} retarget=${{retarget}} nosnap=${{nosnap}} prefetch=${{prefetch}} maxwait=${{maxwait}} box=${{boxOk}} xonly=${{xonly}} zmode=${{zmode}} densityLit=${{densityLit}} drill=${{drilled}} pending=${{pending}} dblend=${{dblend}} dseq=${{dseq}} hov=${{hov}} sstale=${{sstale}} sfresh=${{sfresh}} srestore=${{srestore}} plut=${{plut}} reg=${{reg}} refresh=${{refresh}} dpick=${{dpick}} hold=${{hold}} zoomout=${{zoomout}} broad=${{broadfallback}} dying=${{dying}} dback=${{dback}} dnorm=${{dnorm}} dnormDone=${{dnormDone}} stale=${{stale}} thrash=${{thrash}} qwire=${{qwire}} stream=${{stream}} tj=${{Math.round(maxJump*100)}} td=${{Math.round(reviveDip*100)}} malformed=${{malformed}} pixdet=${{pixdet}} splitbuf=${{splitbuf}} barBase=${{barBase}} histBase=${{histBase}} edgepad=${{edgepad}} mgrad=${{mgrad}} axisontop=${{axisontop}} mtipbase=${{mtipbase}} mcorner=${{mcorner}} mstroke=${{mstroke}} bgrad=${{bgrad}} bcorner=${{bcorner}} msmooth=${{msmooth}} bgocc=${{bgocc}} meancolor=${{meancolor}} dretire=${{dretire}}`;
+    const base=`XY_OK lit=${{lit}} total=${{w*h}} labels=${{labels}} pick=${{hits}} row=${{hasXY}} selAll=${{selAll}} selSome=${{selSome}} active=${{active}} btns=${{btns}} modebarHidden=${{modebarHiddenAtRest}} modebarTopLeft=${{modebarTopLeft}} modebarHover=${{modebarHoverReveal}} modebarNoCollapse=${{modebarNoCollapse}} modebarMenu=${{modebarMenu}} modebarDrag=${{modebarDrag}} modebarSelect=${{modebarSelect}} lassoEdit=${{lassoEdit}} modebarExport=${{modebarExport}} panToggle=${{panToggle}} zin=${{zin}} smooth=${{smooth}} labelThrottle=${{labelThrottle}} hoverSkip=${{hoverSkip}} zanch=${{zanch}} retarget=${{retarget}} nosnap=${{nosnap}} prefetch=${{prefetch}} maxwait=${{maxwait}} box=${{boxOk}} xonly=${{xonly}} zmode=${{zmode}} densityLit=${{densityLit}} drill=${{drilled}} pending=${{pending}} dblend=${{dblend}} dseq=${{dseq}} hov=${{hov}} sstale=${{sstale}} sfresh=${{sfresh}} srestore=${{srestore}} plut=${{plut}} reg=${{reg}} refresh=${{refresh}} dpick=${{dpick}} hold=${{hold}} zoomout=${{zoomout}} broad=${{broadfallback}} dying=${{dying}} dback=${{dback}} dnorm=${{dnorm}} dnormDone=${{dnormDone}} stale=${{stale}} thrash=${{thrash}} qwire=${{qwire}} dwire=${{dwire}} drestore=${{drestore}} stream=${{stream}} tj=${{Math.round(maxJump*100)}} td=${{Math.round(reviveDip*100)}} malformed=${{malformed}} pixdet=${{pixdet}} splitbuf=${{splitbuf}} barBase=${{barBase}} histBase=${{histBase}} edgepad=${{edgepad}} mgrad=${{mgrad}} axisontop=${{axisontop}} mtipbase=${{mtipbase}} mcorner=${{mcorner}} mstroke=${{mstroke}} bgrad=${{bgrad}} bcorner=${{bcorner}} msmooth=${{msmooth}} bgocc=${{bgocc}} meancolor=${{meancolor}} dretire=${{dretire}}`;
     const baseWithStyle=`${{base}} vstyle=${{vstyle}}`;
     // Responsive: 100%-by-100% chart in a 400x300 container tracks its parent;
     // growing the container must fire the ResizeObserver and re-render bigger.
@@ -1398,6 +1427,8 @@ def main() -> None:
     stale = int(re.search(r"stale=(\d+)", title).group(1))
     thrash = int(re.search(r"thrash=(\d+)", title).group(1))
     qwire = int(re.search(r"qwire=(\d+)", title).group(1))
+    dwire = int(re.search(r"dwire=(\d+)", title).group(1))
+    drestore = int(re.search(r"drestore=(\d+)", title).group(1))
     stream = int(re.search(r"stream=(\d+)", title).group(1))
     malformed = int(re.search(r"malformed=(\d+)", title).group(1))
     pixdet = int(re.search(r"pixdet=(\d+)", title).group(1))
@@ -1564,6 +1595,16 @@ def main() -> None:
         )
     if qwire != 1:
         raise SystemExit("log-u8 density decode failed (quantized wire)")
+    if dwire != 1:
+        raise SystemExit(
+            "direct-wire density failed (reduced motion must upload the "
+            "log-u8 wire bytes verbatim and retain them on density.wire)"
+        )
+    if drestore != 1:
+        raise SystemExit(
+            "direct-wire home restore failed (null-grid density must "
+            "re-upload from the retained wire bytes, not throw)"
+        )
     if meancolor != 1:
         raise SystemExit(
             "mean-color density failed (surface must wear the per-cell mean "

spec/design/lod-architecture.md

@@ -376,6 +376,13 @@ invariants so future kinds don't regress them:
 - **T4 — normalization is eased, never stepped** (exposure-style normMax) —
   count-only surfaces; a mean-color texture's physical alpha is
   max-independent, so it has no normalization to ease.
+  When there is nothing to ease, the wire bytes ARE the texture: a
+  count-only `log-u8` reply under `prefers-reduced-motion` pins normMax at
+  the reply's own `max`, so decoding to floats and re-encoding against that
+  same max is the identity. Those replies upload `buf` straight to R8
+  (`lodUploadWireGrid`) and keep `grid` null, retaining the wire bytes so the
+  `_homeDensity` restore (T7) can re-upload after the buffer is gone. Every
+  other reply still decodes through `_uploadGrid`.
 - **T5 — stale replies die:** seq on view updates, drill_seq on subsets,
   pending-view hold for prefetched drills.
 - **T6 — invalid requests do not mutate:** malformed viewport/screen requests