howto use software rendering for developing/debugging on linux

[abma]

mesa has a nice feature: it allows to enable pure software rendering by an environment variable (llvmpipe). to run spring with software rendering only, just run spring with this command:

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LIBGL_ALWAYS_SOFTWARE=1 ./spring

there are a lot of other env vars which can be used to configure behaviour. also driconf can be used to configure mesa.
http://www.mesa3d.org/envvars.html

Notes/Issues:

- (afaik) this only works with opensource (Mesa/Gallium) drivers!
- FSAALevel = 0 has to be set (else i got the error "Couldn't find matching GLX visual")
- SIGNAL_NANS=FALSE has to be set, else a SIGFPE happens in swrast_dri.so

this feature could be useful:
- to run automatic tests on servers
- debug / improve gfx (mesa drivers are imo the reference implementation of opengl)
- test shaders
- make spring run on computers without a gfx card
- create (reproduceable) screenshots on a headless computer
- ...

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Xvfb :5 -screen 0 1024x768x24 &
DISPLAY=:5 ./spring

a screenshot can be made this way:

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xwd -display :5 -root -out image.xwd

[Anarchid]

Thanks! Now i can into texture2 on shitty intels!