Update morphAttributes on geometry

[burnt lotus]

I know as of now morphAttributes cannot be updated on BufferGeometry without creating new instance. But after going through the discussion here: https://github.com/mrdoob/three.js/issues/24243, I got to know something can be done about this.

I looked into source and found this is responsible for uploading morphs to GPU: https://github.com/mrdoob/three.js/blob/6a101b4bffdf5b00d24931c2e50817d3a179fa25/src/renderers/WebGLRenderer.js#L1868-L1872

could someone help me how to properly update morphAttributes whenever I wish to?

[bronze merlin]

well, mugen pretty much told you what to do

b) the count of morph targets has been changed

add/remove a dummy target every time

and I assume this applies to webgl2

[burnt lotus]

thanks, I think adding a condition here triggers upload, without the dummy target. Although that requires modifying three.js.

if ( entry === undefined || entry.count !== morphTargetsCount || object.morphAttributesNeedsUpdate ) {

[bronze merlin]

well if "entry" is something that comes from user-controlled code or at least could be accessed from there, you could define a getter for count that would *cough count the number of reads and supply different value at the time when it's read in that condition

super-hacky but might work 🤣

or maybe that should be done for morphTargetCount origin

just a general idea. I used to successfully fight against double-draw of transparent objects when it was introduced using this method

[burnt lotus]

oh you used the read count and worked with that?!

[bronze merlin]

yes, see https://jsfiddle.net/ny7uco8a/1/ (does not work - and is not needed - now since they added material.forceSinglePass)

but still goes to show how far this kind of trick can take you

[burnt lotus]

after seeing this, i think dummy targets idea is better. because the moment there is one more read call, this breaks right?

[bronze merlin]

of course. but there is new Error().stack if you want to keep digging the hole

[burnt lotus]

woah, super unconventional to get the caller

[bronze merlin]

to get all the callers

and run regexp on them 🥲

[burnt lotus]

https://tenor.com/view/austin-powers-dangerously-gif-20939086

Can break any moment

[bronze merlin]

I mean, three.js semver starts with 0

it is expected to break