Grease Pencil, drawing straight lines v 2.78 I am trying to find the focal length and camera position using the BLAM addon for the image below:



I try to draw the required lines in red (entering CTRLDLMB) but blender only draws horizontal lines and vertical lines. What did I forget to do ?
To draw straight lines select Draw>Line on the grease pencil section.



Otherwise press CtrlD and place the cursor on the starting point of the straight line, then release the Ctrl key while still holding the D key, and position the end point of the line and release the D key.