Extracted lightmap cache functionality from meshInstance to RefCountedCache (playcanvas#3154)

mvaligursky · Martin Valigursky · web-flow · commit 57d7ad8bc5d1 · 2021-05-10T08:37:03.000-07:00
Co-authored-by: Martin Valigursky &lt;mvaligursky@snapchat.com&gt;
diff --git a/src/core/ref-counted-cache.js b/src/core/ref-counted-cache.js
@@ -0,0 +1,36 @@
+// Class implementing reference counting cache for objects
+class RefCountedCache {
+    constructor() {
+        // The cache. The key is the object being stored in the cache.
+        // The value is ref count of the object. When that reaches zero,
+        // destroy function on the object gets called and object is removed
+        // from the cache.
+        this.cache = new Map();
+    }
+
+    // add object reference to the cache
+    incRef(object) {
+        const refCount = (this.cache.get(object) || 0) + 1;
+        this.cache.set(object, refCount);
+    }
+
+    // remove object reference from the cache
+    decRef(object) {
+        if (object) {
+            let refCount = this.cache.get(object);
+            if (refCount) {
+                refCount--;
+                if (refCount === 0) {
+                    // destroy object and remove it from cache
+                    this.cache.delete(object);
+                    object.destroy();
+                } else {
+                    // update new ref count in the cache
+                    this.cache.set(object, refCount);
+                }
+            }
+        }
+    }
+}
+
+export { RefCountedCache };
diff --git a/src/scene/mesh-instance.js b/src/scene/mesh-instance.js
@@ -1,3 +1,4 @@
+import { RefCountedCache } from '../core/ref-counted-cache.js';
 import { BoundingBox } from '../shape/bounding-box.js';
 import { BoundingSphere } from '../shape/bounding-sphere.js';
 
@@ -168,33 +169,17 @@ class MeshInstance {
     static lightmapParamNames = ["texture_lightMap", "texture_dirLightMap"];
 
     // cache of lightmaps internally created by baking using Lightmapper
-    // the key is the lightmap (texture), the value is reference count .. when it reaches 0, the lightmap gets destroyed.
     // this allows us to automatically release realtime baked lightmaps when mesh instances using them are destroyed
-    static _lightmapCache = new Map();
+    static _lightmapCache = new RefCountedCache();
 
     // add texture reference to lightmap cache
     static incRefLightmap(texture) {
-        let refCount = MeshInstance._lightmapCache.get(texture) || 0;
-        refCount++;
-        MeshInstance._lightmapCache.set(texture, refCount);
+        this._lightmapCache.incRef(texture);
     }
 
     // remove texture reference from lightmap cache
     static decRefLightmap(texture) {
-        if (texture) {
-            let refCount = MeshInstance._lightmapCache.get(texture);
-            if (refCount) {
-                refCount--;
-                if (refCount === 0) {
-                    // destroy texture and remove it from cache
-                    MeshInstance._lightmapCache.delete(texture);
-                    texture.destroy();
-                } else {
-                    // update new ref count in the cache
-                    MeshInstance._lightmapCache.set(texture, refCount);
-                }
-            }
-        }
+        this._lightmapCache.decRef(texture);
     }
 
     get renderStyle() {
