Why weight paint work bad?

when i try to paint the weight of some vertices left it’s always a pain, i click many times on it, have to change the angle etc and it still don’t work or so bad… (video here illustrates it : https://drive.google.com/file/d/1hm7dzDPbsuKU1WBXRhDzpdCR2oM3xbJC/view )
Am i doing something bad or the software is bad?

In many cases, automatic weight is incoherent and so weight painting manually is the only solution. So make it working normally would be really helpfull… thanks for any info!

I don’t have a solutions, but I share this frustration. Might have to do with how Blender calculates how a brush affects a vertex; it seems like the size of the brush has less to do with painting than how close the center is to a particular vertex. I know with denser meshes I have less trouble, but weight paint is already so slow that I like to use it on lighter meshes.

I’m hoping that some of the upcoming changes to Vertex Paint help this perform better and more intuitively.

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At least it’s good to know i’m not the only getting this problem and it’s coming more from the software than my way to use it. Sometimes my automatic weight make non sense too.
I guess Blender still have problems and requirs a lot of patience to make things works, even if it make awesome progress on many parts

You just need to know which tool to use in every situation. Individual vertices’ weights can be edited numerically in Edit mode (N panel - Item - there is Vertex Weights section for a selected vertex). You can also copy weights from an active vertex to all selected. For assigning the same weights to large groups of vertices, use Edit mode selection + Vertex Groups => Assign from Object Data tab. Automatic weighting has its own requirements. Assign Automatic From Bones (by “bone heat”) is designed to work with “watertight”, nonzero volume meshes without holes. Assign from Envelopes requires envelope radius to be set up by editing your armature

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That’s really usefull tips and i’m curious to know how you got all that knowledge, thanks

But imagine a case where i have all my vertex differently weighted because of a complex organic mesh, and one of them is screwed up and not selectable in Weight paint mod (like in my vid).
When i’m back in edit mode, the mesh go back to it’s rest pose, how i’m supposed to guess the vertex in question and fix it without risking to screw the weight of the others?

Weight paint is lame and hopefully they’ll fix it, but that’s still great to have ways to get around the problem. Also i don’t really get what you say in the two last sentences, due to my lake of knowledges.

Anyways the current problem here is solved, even if i already have now two others and so i think i’ll repost soon haha, ty again

Armature (and the most modifiers) has an option to display it in Edit mode

First two buttons next to modifier name are On Cage (sync the edit cage with result of modifier) and Display on Edit (doesnt affect the “cage”, merely displays the result)

And those sentences were about two possible automatic weighting options in Blender. Weight Paint mode - Weights - Assign Automatic From Bones (or From Envelopes)

I learn a lot here, thanks again!

I am blender user for years. Recently I switched to new version of blender (2.8+) and can say from my perspective that weight painting in new blender is nightmare. I find it very unintuitive UI and sometimes weird weight paint brush behavior. I have character I need to weight paint after strugling for hours in 2.93 I ended with appening model from 2.93 blend file in 2.79 and made weight paint in less than half hour. Result is more than satisfying. No idea how they could broke features that worked great in old blender. So my workaround is to use old blender for certain tasks like weight painting. Cheers!

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You can also select vertices from weight paint mode by hitting v (there’s a toggle in the header)

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cool option, but personally i tested and the non reacting vertex (like in video) still do not react in weight paint even after being selected

Yes i remember now i had the same constatation when changed from 2.79 to 2.8. Weight paint just work really better in -2.8 versions.
I also had to append characters back to 2.79 many times to rig them with weight paint. I then forgot it while using 2.8+ versions but will probably have to come back to this solution sometimes since even with help here these problems are not totally solved and just happening too much.
Thanks for reminded me this!

I can’t see the video. Vertex and face mask work fine for me. Surely there’s something with the brush you are using

here is another exemple : https://drive.google.com/file/d/1Sje73N05Iflw8-nn5bFL6x9vLE9hnlgt/view
happy to know any brush option that could solve this

Oh ! it’s simply that weight paint only works with surfaces, so clicking on empty space won’t do anything. It’s the same in Maya (not sure about other software).
Not sure how you got those spikes in the first place but you can simply select them and copy weights from adjacent vertices, from either edit or weight paint mode (with “v”). There’s a panel for controlling weights in the sidebar.