Add support for attribute.dirty

[vorg]

We need a way to update only one attribute e.g. offsets without re-uploading all others. One solution would be to add .dirty = true/false property. This could be also used for invalidating bouds and and manually asking for recalculating bounding box.

[dmnsgn]

Revived instancing example and use it to demo attribute.dirty: 13ed415#diff-b9928ed31347ca26a5db354cc663e6275c0a7266edafd38ca237539ca95d2cd0R184-R188

The main change in the system are:

• checking cached object difference upfront and updating properties:

pex-renderer/systems/geometry.js

Lines 53 to 65 in 13ed415

	const geometryDirty = cachedGeom.geometry !== geometry;
	// Cache properties
	if (geometryDirty) {
	if (geometrySystem.debug) {
	console.debug("geometry-system", "update geometry", id, geometry);
	}
	cachedGeom.geometry = geometry;
	cachedGeom.instances = geometry.instances;
	cachedGeom.count = geometry.count;
	cachedGeom.primitive = geometry.primitive;
	}

• checking for both upfront whole geometryDirty and attribute.dirty to skip update:

pex-renderer/systems/geometry.js

Line 92 in 13ed415

if (!(geometryDirty || attributeValue.dirty)) continue;

[dmnsgn]

Performance in example (updating offsets/rotations/colors only instead of positions/normals/uvs/cells/offsets/scales/rotations/colors): 10ms -> 3.5ms