Holding CTRL has interfering functions that cause a crash

Unreal Engine 4.3, Windows 7 64 bit, EVGA GTX 680 superclock

CTRL + Left mouse button has 2 functions

  1. Movement constrained to 1 axis.
  2. Selecting multiple actors, vertices, faces .etc

These 2 functions interfere with each other when trying to select multiple vertices in geometry mode. When clicking several vertices (holding CTRL), UE4 will detect the slightest mouse movements and then move the selected vertices. This causes tremendous lag (I believe UE4 is trying to select and move actors at the same time) which can sometimes crash UE4. If the engine does not crash, undo (CTRL + Z) will sometimes crash the program as well.

What I’m wondering is if there is a way to turn off the option to constrain movement to one axis when holding CTRL. It’s a feature that I do not use since there are easier/alternative ways of constraining movement to one axis.


I went through the editor preferences for key bindings to see if there was something in there that could be disabled and when I couldn’t find a solution I reached out to one of the developers to see if there was a way to disable this in the engine or even by manually editing some of the config files for that key binding.

At the moment any key bindings that are associated with the mouse buttons are hard coded and cannot be unbound, at least for right now. This will be considered for future releases.

As for the crash, I was not able to reproduce this, but it is known that BSPs can be finicky.

Can you provide some repro steps that cause this to happen in a new scene starting fresh? The easier it is to reproduce the easier it will be to track down and fix.

And since you are experiencing a crash, can you please provide us with the .LOG and .DMP files from your [project]\Saved\Logs folder. Additionally, you can please send us the CrashReportClient.log file located in C:\Program Files\Unreal Engine\4.0\Engine\Programs\CrashReportClient\Saved\Logs.

On a Mac, the logs are located in: /Users/UserName/Library/Logs/Unreal Engine/(project name)Editor/ The Library Folder is hidden by default. The easiest way to get to it is by having finder the active application and while holding Option Click Go in the Mac Menu Bar. This will expose Library.

Thank you!



Please find attached several .LOG files and .DMP files from some crash instances.

As for the CrashReportClient.log, the only one I could find was in the 4.2 folder and it’s dated before these crashes happen. The \CrashReportClient\ folder does not exist in the 4.3 folder. (or elsewhere on the computer)

As for steps to replicate. (This is exactly what I did)

  1. Create a cylinder brush.
  2. Make it have a bunch of sides (60-80)
  3. Make it hollow. (I had 2300 outer radius, 2100 inner)
  4. Select the cylinder and go into geometry mode.
  5. Hold CTLR and select several vertices.
  6. Holding CTRL restricts movement to 1 dimension, clicking down on the mouse can cause selected vertices to attempt to move.
  7. If vertices move, hit CTRL+Z (twice).

The crash sometimes happens when UE4 is trying to move vertices if there are many selected. If it doesn’t crash, CTRL+Z will sometimes cause a crash.

I have had to hit CTRL+Z twice because the vertices were moved and then the one I clicked is selected. When I hit CTRL+Z I get something like.

  1. Undo Select Actor
  2. Undo Move

In all cases, the movement causes extreme lag. I have a pretty solid rig, it shouldn’t be experiencing 30+ seconds of lag sometimes. I believe UE 4 is trying to select and move simultaneously.

(NOTE: Snapping on/off makes a difference in the lag, and the amount of movement (obviously). Thus far my solution has been to set snapping really high so that the vertices don’t move (because the snap is too far) but every time they “want to move” the program lags like crazy)

link text


I wasn’t able to get this to repro on my end unfortunately. I did submit the report with your crash logs and dmp along with all your information here for repro to help prevent this type of crash in the future.

Thank you for all the information you’ve provided! :slight_smile: