demo: Fix color scaling behavior for simplification #nojira

When simplifying meshes, we no longer need to divide by 255 because
BufferAttribute.getX will do this for us as of three.js 144. This was
missed during a three.js version upgrade which broke attribute awareness
in the demo by using very small color values that ended up not affecting
the simplification result.

When simplifying points, we are converting typed arrays without any
normalization; as such, we need to normalize these by applying the
scaling factor to color weight.

demo/simplify.html

@@ -136,13 +136,14 @@
 
 					var attrib_weights = [
 						settings.normalWeight, settings.normalWeight, settings.normalWeight,
-						settings.colorWeight / 255, settings.colorWeight / 255, settings.colorWeight / 255,
+						settings.colorWeight, settings.colorWeight, settings.colorWeight,
 					];
 				}
 
 				var flags = [];
-				if (settings.lockBorder)
+				if (settings.lockBorder) {
 					flags.push("LockBorder");
+				}
 
 				var threshold = Math.pow(10, -settings.errorThresholdLog10);
 				var stride = (geo.attributes.position instanceof THREE.InterleavedBufferAttribute) ? geo.attributes.position.data.stride : 3;
@@ -176,9 +177,12 @@
 				var pos_stride = (geo.attributes.position instanceof THREE.InterleavedBufferAttribute) ? geo.attributes.position.data.stride : 3;
 				var col_stride = (geo.attributes.color instanceof THREE.InterleavedBufferAttribute) ? geo.attributes.color.data.stride : geo.attributes.color.itemSize;
 
+				// note: we are converting source color array without normalization; if the color data is quantized, we need to divide by 255 to normalize it
+				var colorScale = geo.attributes.color && geo.attributes.color.normalized ? 255 : 1;
+
 				console.time('simplify');
 
-				var res = MeshoptSimplifier.simplifyPoints(positions, pos_stride, target, colors, col_stride, settings.colorWeight);
+				var res = MeshoptSimplifier.simplifyPoints(positions, pos_stride, target, colors, col_stride, settings.colorWeight / colorScale);
 
 				console.timeEnd('simplify');
 
@@ -191,10 +195,12 @@
 			{
 				MeshoptSimplifier.ready.then(function() {
 					scene.traverse(function (object) {
-						if (object.isMesh)
+						if (object.isMesh) {
 							simplifyMesh(object.geometry);
-						if (object.isPoints)
+						}
+						if (object.isPoints) {
 							simplifyPoints(object.geometry);
+						}
 					});
 				});
 			}
@@ -225,8 +231,7 @@
 
 			function load(path)
 			{
-				if (model)
-				{
+				if (model) {
 					scene.remove(model);
 					model = undefined;
 				}