Knife tool completely non-functional on interior geometry #38623

New Issue

Adam Friesen · 2014-02-13T20:40:42+01:00

Adam Friesen commented

2014-02-13 20:40:42 +01:00

System Information
Win 7 64 bit, i7 Ivy Bridge CPU, ATI 7xxx GPU, 16 gigs of RAM

Blender Version
Broken: Latest build tested was done at hash 2038eb1, I don't know if the knife tool ever worked right in this situation.

Short description of error
Open the attached .blend file, press 'K' and try to make a cut, any cut. Notice how Blender acts like the knife tool does not exist, as it's completely unable to do so much as draw the cut line after a segment is confirmed (not to mention being unable to actually 'cut' the geometry). It seems to be that any ray-casting the knife tool does to determine cuts is dependent on exposure to the infinite space outside of the scene, ideally though, you'd think this could be based on exposure to the current position of the view itself. The normals have also been calculate to point inward to show it's not at all related to mesh normals.

Exact steps for others to reproduce the error
Already mentioned above.

BrokenKnife.blend

If this can be fixed before 2.70 is released, then I think anyone who does interior modeling work will be very grateful.

Thanks.

**System Information** Win 7 64 bit, i7 Ivy Bridge CPU, ATI 7xxx GPU, 16 gigs of RAM **Blender Version** Broken: Latest build tested was done at hash 2038eb1, I don't know if the knife tool ever worked right in this situation. **Short description of error** Open the attached .blend file, press 'K' and try to make a cut, any cut. Notice how Blender acts like the knife tool does not exist, as it's completely unable to do so much as draw the cut line after a segment is confirmed (not to mention being unable to actually 'cut' the geometry). It seems to be that any ray-casting the knife tool does to determine cuts is dependent on exposure to the infinite space outside of the scene, ideally though, you'd think this could be based on exposure to the current position of the view itself. The normals have also been calculate to point inward to show it's not at all related to mesh normals. **Exact steps for others to reproduce the error** Already mentioned above. [BrokenKnife.blend](https://archive.blender.org/developer/F77181/BrokenKnife.blend) If this can be fixed before 2.70 is released, then I think anyone who does interior modeling work will be very grateful. Thanks.

Adam Friesen commented

2014-02-13 20:40:42 +01:00

Changed status to: 'Open'

Adam Friesen commented

2014-02-13 20:40:42 +01:00

Added subscriber: @Ace_Dragon

blender-admin commented

2014-02-13 20:40:42 +01:00

#38733 was marked as duplicate of this issue

Adam Friesen commented

2014-02-13 21:31:33 +01:00

Okay, it seems like there's a little more complexity in this issue than meets the eye, I updated the bug demonstration .blend to reflect this

BrokenKnife2.blend

With the first .blend, you notice that you can just work around by cutting the mesh from the outside, so here, you can press 'K' to try to make cuts anywhere on the selected cube which happens to be a part of the same object. Notice how Blender can't do so much as draw the lines showing where the cut will be. After that, go back into object mode, select the red cube, go into edit mode, and try to cut that one. Notice how the Knife tool starts working again when you use it on that object

Apparently, it appears the Knife tool will not work if the cut surface is completely occluded or blocked from the region outside of the scene by the object it is a part of (which includes cutting from inside the object as opposed to from outside), it's as if the tool is using a raycasting system that sends a ray from outside of the scene, whereas you'd think it should come from the position that you're viewing the scene from instead (that is, when in perspective mode).

Okay, it seems like there's a little more complexity in this issue than meets the eye, I updated the bug demonstration .blend to reflect this [BrokenKnife2.blend](https://archive.blender.org/developer/F77185/BrokenKnife2.blend) With the first .blend, you notice that you can just work around by cutting the mesh from the outside, so here, you can press 'K' to try to make cuts anywhere on the selected cube which happens to be a part of the same object. Notice how Blender can't do so much as draw the lines showing where the cut will be. After that, go back into object mode, select the red cube, go into edit mode, and try to cut that one. Notice how the Knife tool starts working again when you use it on that object Apparently, it appears the Knife tool will not work if the cut surface is completely occluded or blocked from the region outside of the scene by the object it is a part of (which includes cutting from inside the object as opposed to from outside), it's as if the tool is using a raycasting system that sends a ray from outside of the scene, whereas you'd think it should come from the position that you're viewing the scene from instead (that is, when in perspective mode).

Campbell Barton was assigned by Sergey Sharybin

2014-02-17 08:33:43 +01:00

Sergey Sharybin commented

2014-02-17 08:33:43 +01:00

Added subscribers: @ideasman42, @Sergey