WebGLGeometries: Ensure wireframes reflect the current geometry data

[Mugen87]

Fixes the problem mentioned in #12771 (comment)

WebGLGeometries now ensures that the wireframe attribute of a geometry is actually updated when the underlying index buffer changes. Before this fix, the wireframe attribute was created once and never updated.

I've created a fiddle with the fixed build in order to illustrate the new behavior:

https://jsfiddle.net/f2Lommf5/15691/

The PR also does an optimization. Before the fix, getWireframeAttribute() always created an array object right here:

three.js/src/renderers/webgl/WebGLGeometries.js

Line 123 in 771b015

var indices = [];

Because of hoisting, it does not matter that the statement was placed after the return. The array was already created at this point. This is now fixed.

[Mugen87]

BTW: Updating the position buffer is no problem since updateWireframeAttribute() creates a new set of indices for the wireframe attribute. Even if the position buffer changes, the indices are still valid.

[mrdoob]

The PR also does an optimization. Before the fix, getWireframeAttribute() always created an array object right here:

three.js/src/renderers/webgl/WebGLGeometries.js

Line 123 in 771b015

var indices = [];

Because of hoisting, it does not matter that the statement was placed after the return. The array was already created at this point. This is now fixed.

Uh oh... Thanks!

[Mugen87]

Because of hoisting, it does not matter that the statement was placed after the return. The array was already created at this point.

Oh sorry, I've made a mistake here. Because of hoisting, the variable indices is just declared and has the value undefined. The array is actually created after the return. So in this context, everything is fine even with the latest builds 😅

[Mugen87]

I think this PR is ready to go now 😊🚀

[Mugen87]

/bump @mrdoob

[Mugen87]

see #10638 (comment)

[Mugen87]

Okay, I've added an additional change to ensure that the respective WebGLBuffer of an obsolete wireframe attribute is actually deleted. This change should prevent an evil memory leak^^

[mrdoob]

Late thanks! 😇