Re: [Visualpython-users] speed

[Bruce S. <Bru...@nc...>]

There is one other approach you could use.

Make the scene invisible while you create the objects. Then make it visible. If 
there are lots of objects, it will take a long time to render the scene, and you 
certainly won't be able to navigate smoothly. But you could have a second window 
with a rudimentary sampled version of the display. Let a click in the second 
window toggle the visibility of the first (main) window. Click to make the first 
window invisible, then navigate in the scene in the second window to get the 
camera the way you want it, then use this information to modify the positioning 
of the camera for the first window, and finally click in the second window to 
make the first window visible with the new viewing angle. Something like that.

The 1/3 factor you're seeing isn't necessarily inefficiencies in VPython's 
having to get things from Python. The little calculation I did is only a rough 
estimate.

Bruce Sherwood

Tim Smith (25121) wrote:
> That's very interesting Bruce, The quadro nvs285 I have in my
> workstation is only rated at 1.5 million triangles per second (I'm
> horrified btw, I asked our IT department what card was in this pc and I
> was told it was a fast quadro), meaning 29,000 sphere's would be the
> maximum I could render and have reasonably smooth motion, I'm finding I
> get 1/3 of that in actual fact when I do tests.
> 
> -----Original Message-----
> From: Bruce Sherwood [mailto:Bru...@nc...] 
> Sent: Tuesday, 17 November 2009 11:50 PM
> Cc: vis...@li...
> Subject: Re: [Visualpython-users] speed
> 
> I'm pretty much out of my depth here, but Guy Kloss's nearly
> simultaneous and 
> very interesting post about speed suggests that there is no royal road
> to speed 
> + rapid creation. For that matter, there's only so much you can get out
> of 
> today's graphics cards.
> 
> For example, the NVIDIA Quadro FX 4600 (about $1400) is rated at 250
> billion 
> triangles per second (http://www.deskeng.com/articles/aaajxm.htm).
> Suppose a 
> small sphere is approximated by 4 triangles facing you. Then the card
> would take 
> a second to display 60 billion small spheres. To have good mouse
> navigation 
> capabilities you would need to be able to redraw the scene in about a
> thirtieth 
> of a second in response to a mouse move, which means that you could
> rotate and 
> zoom only about 2 billion spheres. And that's assuming that no
> computation is 
> being done: you generate the 2 billion spheres once, and then wait to
> react 
> quickly to a change in camera position.
> 
> A midrange card like the $600 Quadro FX 1700 does only 190 million
> triangles per 
> second, which implies about 2 million navigable spheres.
> 
> Bruce Sherwood
> 
> Tim Smith (25121) wrote:
>> Hmm. Would I benefit from writing the application purely in c++ (not
> my
>> preferred option)?
>> I'm treading a line between speed and flexibility of pumping out
> various
>> models, and speed of interpreting the model itself. If the model is
>> frighteningly slow to interact with then I'm sunk, but if it takes me
>> too long to produce a new model I'm also sunk.
>>
> 
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