Track To constraint makes object disappear
Closed, ResolvedPublic

Description

System Information
Win 7 64bit

Blender Version
Broken: 2.79
Worked: 2.78 (fb1cd76)

Short description of error
Track To constraint on straight Z axis is inconsistent

Exact steps for others to reproduce the error
Load default scene, translate Cube to (0, 0, -1.7)
Clear Camera transforms (ALT G, ALT R)
Select Camera and then SHIFT click select Cube
Track (CTRL T) Camera to Cube and select Track To -> Camera shrinks to nothing

File is ready to press CTRL T

Not seeing that here on macOS on either 2.79 release or latest buildbot.

Sergey Sharybin (sergey) triaged this task as Incomplete priority.Dec 4 2017, 10:39 AM

I can not reproduce the issue on neither Linux nor Windows 10, both 64 bit.

  1. Can the issue be reproduced after doing File -> Load Factory settings?
  2. Can the issue be reproduced with latest builds from buidler.blender.org?

If so, please provide .blend file right before you click "Ctrl-T".

Updated first post with file and video.

Latest build and "load factory settings" doesn't help, but I've tried 2.78 (fb1cd76) and it works without problems

Serge Lyatin (SergeL) updated the task description. (Show Details)
Joshua Leung (aligorith) raised the priority of this task from Incomplete to Confirmed.Dec 5 2017, 1:15 PM
Joshua Leung (aligorith) edited projects, added Animation; removed User Interface.

Can confirm on the provided file. This only seems to affect the "TrackTo" constraint, and not the "Damped Track" or "Locked Track"

only happens when camera is exactly above the Cube on the Z-Axis (constraint works normally when you start moving the cube away from that axis)
Not sure why the constraint actually affects scaling at all... will have a look...

Thanks for tracking down the commit. This is quite an edge case - while the vector is normalized it's so close to zero to begin with, a second call is needed to make it really normalized (which fixes the bug).

Since this code was working beforehand, revert my change with comment on why.