Why is commandline rendering slower then rendering in blender?


I’m on linux ubuntu 9.04 using blender 2.49. I want to render my animation from the commandline as blender seems to stop the rendering process when I lock my ubuntu desktop and the commandline continuouse working.

After tracking the times I discover that the same scene takes approximatly 40secs per frame on the commandline and only 25 secs in blender.

Command line used is blender -b blendfile.blend -o //renders/render -S Base -s 1 -e 301 -a

Any reasons why commandline rendering is so much slower? Any tips on improving the commandline rendering speed?

Or does anybody have a tip of preventing blender from stoping rendering when locking the desktop?

Thanks for any replies


This is just a guess, as I don’t have a animation to test with but, you don’t seem to be using the -t option which specifies the number of threads to use. In Blender normal when it start it automatically sets the number of threads to use based on the number of processor cores.

On the command line I am not sure that it does this and so you may need to set the -t option to the number of cores you have.

Thank you for the answer but as far as I can tell 0 (meaning autodetect) is the default on the command line and my cpu monitor tells me that both cores are working at 100%.
My current guess is that it has something to do with setting up the scene and probably with process priority. It seems that blender is reserving a higher priority for the rendering process then the commandline at least as long as it is in the foreground.
could any of the developers tell me if I’m on the right track?


Does using linux’s nice command help in speeding up command line render? Maybe changing the process’s priority manually would help. Though I don’t know if that only works for processes and not threads.

Hey i have a question, first i couldn’t make a no topic for this, for some reason i can’t find the new topic button. Basically my question is, when ever i try to render a current frame to see how everything looks, the picture rendering takes a long long time, why is this? the setting is on 1000x600 on 8-bit

@johnnypro777: To post your own question, go into the forum you need (like “Composition, Visual Effects & Rendering” or “Basics & Interface”). Instead of clicking into other people’s topics, look above or below the list of topics for “>> new thread” -click on that to make your own post.

Right there:-

hahaha, thanks