Just noticed that I am not able to set a source location while using the clone tool (inside of the liquify effect). When pushing the option key (Mac OS), the 3D camera tool shows up.
Thank you for reporting this issue. It appears that the Alt/Option-click for setting the source of Liquify's Clone tool is being intercepted for camera navigation, as you mentioned. We are now looking into fixing this issue, but in the meantime, you can avoid the issue by doing any of the following: - Disable "Activate Alt - Left / Middle / Right mouse click..." in the 3D section of the preferences. - If the layer with Liquify effect applied is 3D, temporarily make the layer 2D by disabling the 3D switch. - Temporarily move or pre-compose the layer with Liquify into a Comp without a 3D Camera.
Thanks again for reporting this issue. - John, After Effects Engineering Team