Cache Source instead of Texture instances in material system (#5455)

Co-authored-by: Noeri Huisman <mrxz@users.noreply.github.com>

Author: mrxz

src/components/material.js

@@ -250,4 +250,13 @@ function parseBlending (blending) {
 function disposeMaterial (material, system) {
   material.dispose();
   system.unregisterMaterial(material);
+
+  // Dispose textures on this material
+  Object.keys(material)
+    .filter(function (propName) {
+      return material[propName] && material[propName].isTexture;
+    })
+    .forEach(function (mapName) {
+      material[mapName].dispose();
+    });
 }

src/core/shader.js

@@ -135,9 +135,6 @@ Shader.prototype = {
         color = new THREE.Color(value);
         return new THREE.Vector3(color.r, color.g, color.b);
       }
-      case 'map': {
-        return THREE.ImageUtils.loadTexture(value);
-      }
       default: {
         return value;
       }