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Box and Lasso select is extremely unreliable in Face or Edge select mode (selects non-visible faces or edges)
Confirmed, NormalPublicKNOWN ISSUE


System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1070 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.82 (sub 6), branch: master, commit date: 2019-12-30 18:20, hash: rB56ef761381ec
Worked: (optional)

Short description of error
Using box select is extremely unreliable while in Face select or Edge select mode (I didn't observe any problems in Vertex mode). It may end up selecting non-visible faces/edges inadvertently and with seemingly no pattern to its misbehavior or workarounds (shrinking range of the clip start/end doesn't fix it, enabling face centers doesn't fix it etc.)

This problem has existed for some time now but today I finally got fed up with it after losing several minutes of work again.

I'm using a hidpi 4k screen, using Blender's UI scaling of 1.0, and OS scaling of 2.0 in case this matters.

Exact steps for others to reproduce the error

  • Start with default .blend
  • Enter edit mode and Subdivide cube twice
  • Switch to Face select mode (or Edge select mode)
  • Attempt to box-select a variety of faces on the cube
  • Notice that more often than not, extra faces which are not visible are still selected

No selection

Selecting all visible faces with box-select

Non-visible faces being selected :(

Non-visible edges being selected :(

Event Timeline

I can confirm this on Linux with a GTX980Ti and a common 1080 resolution. It does seem random though: selection works just fine from the "default" view, but can fail when the object is viewed from other positions/angles.

Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Jan 8 2020, 6:32 PM
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Known Issue".

This also happened in Blender 2.79
Selecting faces in edit mode uses OpenGL to make a drawing that maps all faces within the rectangle.
Some pixels of faces that should be 100% occluded are still drawn. This is because these faces share a same edge as the face that occluded and the threshold between drawing and not the face is hard to distinguish.
I can't think of an efficient solution to this problem.

The precise buffer problem is conceptual and affects many selection scenarios. For example: selection of many small poly from a far distance, selection poly in big angles of view.

Aaron Carlisle (Blendify) reopened this task as Confirmed.Feb 7 2020, 7:37 PM

Seems to still be an issue

Evan Wilson (EAW) renamed this task from Box select is extremely unreliable in Face or Edge select mode (selects non-visible faces or edges) to Box and Lasso select is extremely unreliable in Face or Edge select mode (selects non-visible faces or edges).Feb 8 2020, 4:20 AM
Got a possible solution. Very lightweight, just make an additional bitmap that is the size of the viewport, check if it sees enough verts for any given face. Tell triangles with less than 3 verts visible to go away, quads and ngons need to see at least 4. Triangles have the occasional exception but way better than before and can be avoided usually besides. Going to do edges, should be as simple as if it can see 2 verts, it's all good.