[Bf-committers] sculpt mode wireframe display issue and question

[Sergey Sharybin]

Hey,

Well, not sure why one would want to sculpt in wireframe mode, but ok :)

In my opinion, drawing all edges in non-dyntopo mode is the way to go.
Couple of reasons for this:

- You don't see much details with optimal display, so it's difficult to
predict what stroke would do.
- It makes things consistent with dyntopo sculpt.

I could ask couple of artists here who are doing quite reasonable amount of
sculpting to confirm my expectations about this question.


On Sun, Jul 21, 2013 at 11:07 PM, David Jeske <davidj at gmail.com> wrote:

> I'm trying to fix a bug in sculpt mode display and could use some input...
>
> User problem...
>
> With edges enabled but draw-all-edges disabled, edges between coplanar
> faces are hidden. In sculpt-mode, as the user-sculpts (no dyntopo), the
> co-planar status of edges is not re-evaluated. This means that as edges
> which started hidden remain hidden even as the sculpt brush causes them to
> no-longer be coplanar. --- This is pretty undesirable, because the user
> can't see their work without flipping to edit mode and back.
>
> Obviously the user can turn on draw-all-edges.
>
> If that's the only way sculpt mode visuals work, it probably makes sense to
> just force draw-all-edges during static sculpt -- like is already done in
> weight-paint, and dyntopo sculpt.
>
> If that's a good enough fix, I'll make a patch, and you can all skip the
> rest of this email.
>
> If not, read on, as I could use some advice..
>
> Why it happens and possible fixes...
>
> Sculpt mode (no-dyntopo) draws object wireframes with the same rules as
> object-mode. This means if wireframe is enabled, but draw-all-edges is not,
> it uses the ME_EDGEDRAW status to show/hide each edge. This (basically)
> means that coplanar edges are hidden (see bmesh_quick_edgedraw_flag).
> However, as far as I can see ME_EDGEDRAW is only setup during bulk-convert
> of a BMesh into a Mesh for display.
>
> In theory, I think the "best" solution would be to recalc the ME_EDGEDRAW
> flag status only for edges of vertices which are moved by a static sculpt
> brush. However, if I'm reading the code correctly, there isn't (currently)
> any quick way to correlate the BMEdge edge structure with the MEdge entry
> that contains the flag... -- am I reading that right?
>
> If I got that right, some paths to fix this might be...
>
> 1) have static-sculpt build a BMEdge to MEdge hashmap so it can efficiently
> update edge-draw flags for moved edges and their neighbors (more memory
> usage, but should be very little performance hit during sculpt)
>
> 2) force recalc of the MEdge list when co-planar edges are moved. (only
> costs something when coplanar edges are moved, but that cost is
> proportional to mesh size so it could be large)
>
> 3) ... and of course, as I mentioned above -- force draw-all-edges during
> sculpting (more draw cost to draw all edges, depending on model)
>
> Thoughts?
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-- 
With best regards, Sergey Sharybin