#1
I've been playing around with firealpaca(it's also a free painting application uses QT) and noticed it has a very interesting approach in 'snap' feature, which is an equivalent of assistant in krita.





1 Besides options mainly used for 2D shapes(parallel lines, grid, radial, circle, curve, etc), it has a mini 3d object simulator, and makes the simulated projection a 'layer'.
2 If the layer is visible and the '3D Perspective Snap' option is on, the perspective snap feature takes effect.
3 You can select a specific object in the layer that you want to enable for snapping, with snap setting button.

https://www.youtube.com/watch?v=BSTUUSP3auU

I'm not sure how the idea can be applied to krita, but for users who want to draw stuffs in perspectives, using editable hexahedrons (instead of setting up many vanishing points and parallel lines manually) could be very, very practical. Because a hexahedron automatically sets hypothetical vanishing points by itself anyway, in 100% accuracy.


#2
When 'Snap to Assistants' option is off and Assistant tool is not selected, it's better for assistants to be automatically invisible on the canvas.
I see no reasons to keep it in the current way.

I remember there was a person on the IRC some months back that modified the code to show an adjustable 3D axis assistant like that, even allowing for fisheye type distortion of the lines - but it was just a personal project of theirs and never attempted for it to get merged.
I would love to see something like that added to Krita, as well. Currently, I tend to make simple wireframe renders with a desired camera setup in Blender, add that as a background layer and align Perspective or Vanishing Point assistants to it, if needed.

Regarding #2 - I disagree, even with snapping disabled the assistants and their previews through the cursor can serve as visual helpers when checking if painted elements are laid out correctly. For example, the preview that traces a straight line from the cursor to a vanishing point is great to check if some painted element aligns in position and projected size with other elements further along the imaginary perspective. That is my main reason for using assistants, I rarely if ever activate the snapping feature. There's always the option to disable showing assistants and previews separately under the View menu.

Well, it won't hurt to make it as an option. I'm sure there are people like me too out there.
Or, the opacity of assistants can be lowered when snapping is disabled at least.

#3
Snapping among assistants would be nice? Espacially, vanishing points often should be aligned at the same eye level, and it's not easy to do that fast. I often zoom in the canvas and move assistants pixel by pixel to match the exact level.

Just ideas.

I don't think I ever used "snap to assistants", although I use them quite regularly. I want to draw myself after all, and snapping just makes it stand out as not drawn by hand too much.

Snapping control points would be nice though, among many other things that could be done.

@Snudl, are you referring to David Revoy's Mockup by any chance? I wouldn't know of anyone actually writing/having written code, it just came up again on a discussion about the current not-so-efficient rendering of assistants and other usability issues.
But I'm not in chat 24/7...reading backlog when I'm AFK during the day already eats enough time

Snapping between assistants, if at all possible, would be great.

Some features that are already planned or considered:
* Assistant layers / masks - https://phabricator.kde.org/T1616
* Converting vectors to assistants - https://phabricator.kde.org/T1617
* More types - https://phabricator.kde.org/T6543
* Select and transform assistants - https://bugs.kde.org/show_bug.cgi?id=331790

Transforming assistants is already indirectly possible in current master and should be included in the 4.3 release - Using the scale, rotate, shear transform operations under the Image menu now also transforms the assistants with the image contents.

@Lynx3d, no if I'm not mistaken it was someone I hadn't seen in the chat before and posting videos of his work. Unfortunately I couldn't find it in the old log anymore, so I'll have to ask if anyone remembers.

@Snudl, do you may refer to Wysteriary?
I know he/she was working a few months back on the assistant tool.
The most recent video I could find showing his/her progress: https://imgur.com/a/78FIcHF

@jasperh Thanks for letting me know, I talked to Wysteriary. Would be great to have, current progress is in this branch:
https://invent.kde.org/nmaghfurusman/kr ... nts-2pp-vp
Crazy thing is, I'm sure I saw a different demonstration, but Wysteriary and others I explained it to weren't aware either.