Fix reference counting for SplatAccumulator during updates

Author: mrxz

src/PackedSplats.ts

@@ -464,7 +464,7 @@ export class PackedSplats {
     let maxSplats = 0;
     const mapping = splatCounts.map((numSplats) => {
       const base = maxSplats;
-      // Generation happens in horizonal row chunks, so round up to full width
+      // Generation happens in horizontal row chunks, so round up to full width
       const rounded = Math.ceil(numSplats / SPLAT_TEX_WIDTH) * SPLAT_TEX_WIDTH;
       maxSplats += rounded;
       return { base, count: numSplats };

src/SparkRenderer.ts

@@ -314,6 +314,7 @@ export class SparkRenderer extends THREE.Mesh {
     this.splatEncoding = options.splatEncoding ?? { ...DEFAULT_SPLAT_ENCODING };
 
     this.active = new SplatAccumulator();
+    this.active.refCount = 1;
     this.accumulatorCount = 1;
     this.freeAccumulators = [];
     // Start with the minimum of 2 total accumulators
@@ -765,7 +766,7 @@ export class SparkRenderer extends THREE.Mesh {
       // minimum co-orientation (dot product of quaternions)
       const originChanged = !withinCoorientDist({
         matrix1: originToWorld,
-        matrix2: this.active.toWorld,
+        matrix2: accumulator.toWorld,
         maxDistance: 0.00001,
         minCoorient: 0.99999,
       });

src/SparkViewpoint.ts

@@ -479,9 +479,15 @@ export class SparkViewpoint {
         // Splat mapping has not changed, so reuse the existing sorted
         // geometry to show updates faster. We will still fire off
         // a re-sort if necessary. First release old accumulator.
+        accumulator.refCount += 1;
         this.spark.releaseAccumulator(this.display.accumulator);
         this.display.accumulator = accumulator;
+        this.display.viewToWorld.copy(this.viewToWorld);
         displayed = true;
+
+        if (this.spark.viewpoint === this) {
+          this.spark.prepareViewpoint(this);
+        }
       }
     }
 
@@ -509,15 +515,12 @@ export class SparkViewpoint {
     }
 
     if (accumulator) {
-      // Hold a reference to the accumulator so it isn't released
+      // Hold a reference to the accumulator for sorting
       accumulator.refCount += 1;
     }
 
-    if (
-      accumulator &&
-      this.pending?.accumulator &&
-      this.pending.accumulator !== this.display?.accumulator
-    ) {
+    if (this.pending?.accumulator) {
+      // Release the reference of the pending accumulator
       this.spark.releaseAccumulator(this.pending.accumulator);
     }
     this.pending = { accumulator, viewToWorld: this.viewToWorld, displayed };
@@ -533,9 +536,10 @@ export class SparkViewpoint {
       }
 
       const { viewToWorld, displayed } = this.pending;
-      let accumulator = this.pending.accumulator ?? this.display?.accumulator;
+      let accumulator = this.pending.accumulator;
       if (!accumulator) {
-        accumulator = this.spark.active;
+        // Hold a reference to the accumulator while sorting
+        accumulator = this.display?.accumulator ?? this.spark.active;
         accumulator.refCount += 1;
       }
       this.pending = null;
@@ -546,6 +550,10 @@ export class SparkViewpoint {
       this.sorting = { viewToWorld };
       await this.sortUpdate({ accumulator, viewToWorld, displayed });
       this.sorting = null;
+
+      // Release the reference to the accumulator
+      this.spark.releaseAccumulator(accumulator);
+
       // Continue in loop with any queued sort
     }
   }
@@ -668,13 +676,18 @@ export class SparkViewpoint {
     displayed?: boolean;
   }) {
     if (!this.display) {
+      // Hold a reference to the accumulator while part of display
+      accumulator.refCount += 1;
       this.display = {
         accumulator,
         viewToWorld,
         geometry: new SplatGeometry(ordering, activeSplats),
       };
     } else {
       if (!displayed && accumulator !== this.display.accumulator) {
+        // Hold a reference to the new accumulator being displayed
+        accumulator.refCount += 1;
+        // Release the reference to the previously displayed accumulator
         this.spark.releaseAccumulator(this.display.accumulator);
         this.display.accumulator = accumulator;
       }