WebGLBindingState: Add geometry.index cache for VAO

Now, the needsUpdate method only compares geometry.attributes, if i change geometry.index when using VAO, it may cause bugs.

Add geometry.index cache for VAO will help:

        function needsUpdate( geometry ) {

		const cachedAttributes = currentState.attributes;
		const geometryAttributes = geometry.attributes;

		if ( Object.keys( cachedAttributes ).length !== Object.keys( geometryAttributes ).length ) return true;

		for ( const key in geometryAttributes ) {

			const cachedAttribute = cachedAttributes[ key ];
			const geometryAttribute = geometryAttributes[ key ];

			if ( cachedAttribute.attribute !== geometryAttribute ) return true;

			if ( cachedAttribute.data !== geometryAttribute.data ) return true;

		}

		if ( currentState.index !== geometry.index ) { // Fix!!

			return true;

		}

		return false;

	}

        function saveCache( geometry ) {

		const cache = {};
		const attributes = geometry.attributes;

		for ( const key in attributes ) {

			const attribute = attributes[ key ];

			const data = {};
			data.attribute = attribute;

			if ( attribute.data ) {

				data.data = attribute.data;

			}

			cache[ key ] = data;

		}

		currentState.attributes = cache;
		currentState.index = geometry.index; // Fix!!
	}

[shawn0326]

Ok, I’d like to make PR.

[takahirox]

Yes, this is actually a bug. Good catch and sorry for the bug!

Probably, as you suggested, we need to cache index and check it.

@shawn0326

Would you like to make PR to fix? Or do you want me to make?

@Mugen87

If I reuse the same material, everything works fine

it probably works since in my modified example only a single VAO exists (because there is only a single program).

Correct, if you reuse the same material in the example only a single VAO exists so you don’t see the problem.