blender
/
blender
136
404
Fork 586
Code Issues 6.2k Pull Requests 758 Projects 19 Wiki Activity

Docs: add diagrams describing the purpose of BMwEdgeLoopWalker.f_hub 

Without this the purpose of this feature isn't clear.

While 01b3e9cc9f linked to an image,
add inline ascii diagrams with detailed explanations.
This commit is contained in:
Campbell Barton 2021-01-29 09:43:29 +11:00
parent 71cb6923f5
commit 1e355b0992
Notes: blender-bot 2023-02-14 02:08:37 +01:00 
Referenced by issue #84906, Loop selection corner case
1 changed files with 64 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
source/blender/bmesh/intern/bmesh_walkers_impl.c
View File

@ -863,7 +863,70 @@ static void bmw_EdgeLoopWalker_begin(BMWalker *walker, void *data)
lwalk->is_boundary = BM_edge_is_boundary(e);
lwalk->is_single = (lwalk->is_boundary && bm_edge_is_single(e));
/* could also check that vertex*/
/**
* Detect an NGon (face-hub)
* =========================
*
* The face-hub - #BMwEdgeLoopWalker.f_hub - is set when there is an ngon
* on one side of the edge and a series of faces on the other,
* loop around the ngon for as long as it's connected to faces which would form an edge loop
* in the absence of the ngon (used as the hub).
*
* This isn't simply ignoring the ngon though, as the edges looped over must all be
* connected to the hub.
*
* NGon in Grid Example
* --------------------
* \code{.txt}
* +-----+-----+-----+-----+-----+
* | | | | | |
* +-----va=ea=+==eb=+==ec=vb----+
* | | | |
* +-----+ +-----+
* | | f_hub | |
* +-----+ +-----+
* | | | |
* +-----+-----+-----+-----+-----+
* | | | | | |
* +-----+-----+-----+-----+-----+
* \endcode
*
* In the example above, starting from edges marked `ea/eb/ec`,
* the will detect `f_hub` and walk along the edge loop between `va -> vb`.
* The same is true for any of the un-marked sides of the ngon,
* walking stops for vertices with >= 3 connected faces (in this case they look like corners).
*
* Mixed Triangle-Fan & Quad Example
* ---------------------------------
* \code{.txt}
* +-----------------------------------------------+
* | f_hub |
* va-ea-vb=eb=+==ec=+=ed==+=ee=vc=ef=vd----------ve
* | |\ | | | / / \ |
* | | \ \ | / / / \ |
* | | \ | | | / / \ |
* | | \ \ | / / / \ |
* | | \ | | | / / \ |
* | | \ \ | / / / \ |
* | | \ | | | / / \ |
* | | \ \ | / / / \ |
* | | \| | |/ / \ |
* | | \\|// / \ |
* | | \|/ / \|
* +-----+-----------+-----+-----------------------+
* \endcode
*
* In the example above, starting from edges marked `eb/eb/ed/ed/ef`,
* the will detect `f_hub` and walk along the edge loop between `vb -> vd`.
*
* Notice `vb` and `vd` delimit the loop, since the faces connected to `vb`
* excluding `f_hub` don't share an edge, which isn't walked over in the case
* of boundaries either.
*
* Notice `vc` doesn't delimit stepping from `ee` onto `ef` as the stepping method used
* doesn't differentiate between the number of sides of faces opposite `f_hub`,
* only that each of the connected faces share an edge.
*/
if ((lwalk->is_boundary == false) && (vert_edge_count[0] == 3 || vert_edge_count[1] == 3)) {
BMIter iter;
BMFace *f_iter;