When using the Grease Pencil with either the "Surface" or "Stroke" option, Blender stalls temporarily after each stroke. The length of the stroke seems to have a direct affect on the length of the stall.
The problem occurs in 2.56, 2.57b, and SVN. I am able to repeat the problem consistently on Mac OS X 10.6 but the issue does not happen on Windows 7.
To check for the problem open a default scene, add a new grease pencil layer, change the stroke type to "Surface" and then draw several strokes on the cube. The longer the stroke the longer the stall. I also found that if you draw straight lines with CTRL + D and go over the edge of the cube into 3D space the the stall is much longer.
My Mac OS X machine specs are:
Intel Core i7 2.93, 8 GB Ram, ATI Radeon HD 5750
Description
Event Timeline
Tried your instructions on a 10.5 G5 PPC with ATI 6800 and Intel PowerBook 10.6 with ATI X1600. Grease pencil with "Surface" draws fast and immediately applies surface without disturbing delays. (very long strokes less than half a second).
The code to map strokes on surface grabs the ZBuffer via OpenGL. I've heard some people complain it was slow in other areas where this used too, like for combing hair particles. Reading ZBuffer values is supported in OpenGL since version 1.0, it's a low level basic call... which is unfortunately not implemented well on any driver it seems.
Anyway, you know Blender's using cross-platform identical code for all OSs we support. We really depend on proper opengl implementations here... if this issue keeps working bad for newer OS X systems we should look at different ideas then.
(Moving to opengl tracker to keep track of it in future)
Thanks for the follow-up Ton. I just tested it on my laptop as well, running 10.6.7 on an Intel Core 2 and everything is smooth and fast.