Making VisIt do hardware accelerated parallel rendering
Of course, VisIt only does parallel rendering in its "Scalable Rendering" mode. So that mode must be enabled. If you have lots of geometry, this is done automatically. If not, you can turn on Scalable Rendering mode by going to Options->Rendering and looking under the Advanced tab.
- You tell VisIt to turn on hardware acceleration by setting up a host profile.
- It is common to have two parallel host profiles, one that has HW rendering and one that has SW rendering.
- To make a profile that has hardware acceleration enabled:
- go to the "Advanced options" for that profile in the Host profile window
- go to the sub-tab on "Hardware acceleration"
- turn on the "Use cluster's graphics cards" button.
- NOTE: this button only effects subsequent engine launches. If you have already launched an engine, this will not change that engine's behavior.
- The pre-command and post-command are for the case where you have to start an X-server when you launch VisIt.
- Save your settings if you are planning on having these changes take effect in the next session.
Confirming that you are getting hardware acceleration
There is currently no easy way to confirm that you are getting hardware acceleration. The hard way is to time without hardware acceleration and with hardware acceleration and see if it is faster.
- Launch VisIt as "visit -timing". Use a non-hardware accelerated profile and launch with two processors.
- Go to Options->Rendering and turn Scalable Rendering to "Always"
- Make your visualization window be small (like 100x100 pixels)
- Open up the toy problem "noise.silo" (located in the data directory of your install)
- Make a Contour plot with Nlevels = 50
- Rotate several times
- Now study the timings information:
- Get a prompt on the parallel machine (assuming the parallel machine is different from where your client is)
- In your home directory, there should be a file named "engine_par.000.timing".
- Look for an entry saying "Screen capture for SR took".
- It should be about 0.75 seconds.
- This is the time to do the rendering in software.
- Now shut down VisIt and repeat all steps, but use a hardware accelerated profile this time.
- The timings entry for "Screen capture for SR took" should be much less than 0.75s. If it is, then you have hardware acceleration!