Re: [Visualpython-users] From newbie: major performance woes

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

The beta version is called the beta version because there are problems 
with it, and it's helpful to have your report of what doesn't work; 
there have been almost no reports from Linux users. I normally work on 
Windows but have tested the Linux beta version against a variety of 
applications. I had concluded that the beta version mostly works okay on 
Linux, while there are serious bugs on Windows. You're reporting that it 
isn't okay even on Linux, which I was not aware of.

My own testing was done on a more recent version of Ubuntu, though that 
seems an unlikely issue, and your hardware is certainly adequate 
(presumably your 1.86MHz processor is a typo; it must be 1.86GHz).

Because I'm trying to get into working on the problems with the beta 
version myself, it could be helpful if you would send me an example of a 
program where interactivity is compromised, to add to my suite of test 
programs.

There isn't a simple patch to make the production version have 
transparency. There was a major change in the fundamental architecture 
of Visual to make transparency a possibility.

As stated in the description of the points object, these are circles or 
squares, not spheres, of particular use in plotting graphs. They may or 
may not be of any use to you. I would think that they're a lot faster 
than spheres.

The late Arthur Siegel did experiment a bit with specifying the level of 
detail for the rendering of spheres. There is an undocumented attribute 
of the "display" object:

scene.lod = -3 # range is -6 (low level of detail) to 0 (high)
sphere()

I don't like having negative values for "level of display" (lod), so 
think of this as very experimental, but it will let you try some things. 
Alternatively, since you evidently have a lot of experience, you could 
make changes of your own to the internal workings of Visual to 
experiment with the issues. Thanks much for your report.

Bruce Sherwood

Jiang Qian wrote:
> Hi:
> 	Sorry about the confusing subject line of my last email. I did 
> manage to compile the beta, I just have major performance problem.
> 	I took a look at the code of sphere.cpp, and notice there's 
> discussion about levels of details. I wonder, however, are all that 
> exposed to the user? Is there anyway I can reduce the level of details 
> from my script? Or if that's not possible, is it possible to in fact 
> change the code manually and recompile?
> 	Another issue that may or may not have anything to do with my 
> performance woes. There are several demos in the example directory does 
> not run properly in my installation. Drape shows only a rod. Double 
> pendulum is way slower than in 3.4, Hanoi shows artifacts whenever I 
> move a ring. I'm beginning to think there might be something wrong with 
> my beta installation. How can I check?
> 	Thanks in advance for your help.
> 								Jiang
> 
> On Wed, Nov 07, 2007 at 01:35:57AM -0500, Jiang Qian wrote:
>> Hi all:
>> 	I'm new to this list. I installed the stable visual-3.2.9 and it 
>> worked great. But I really would like to to get the transparency to 
>> work.  So I installed visual 4.beta16. I jumped through all sorts of 
>> hoops, and finally got it to work. The transparency works quite well. 
>> But I have serious performance issue.
>> 	I mainly use visual to visualize packed spheres, and small 
>> particles inside the spaces between them. In visual 3.2.9, a system with 
>> a few hundred spheres packed inside a cube works very smoothly: I can 
>> rotate, zoom at will with middle and right button. By combining the two, 
>> I can essentially "walk" into the sphere packs.(The spheres rendered are 
>> not perfectly smooth, but I manually changed some lines in the source 
>> code to make the smoothness ok). It all works fine, the only thing I 
>> miss is transparency.
>> 	However, in visual 4.beta16, using identical code(with *no* 
>> transparency yet), I get a spectacularly smooth and well lit spheres, 
>> but the tradeoff seem to be heavy performance penalty: I can barely zoom 
>> and move, the rotation is slow. Interactive zooming and rotation is the 
>> key reason why I use visual: otherwise I can just render things in 
>> povray. Needless to say, I would like to find a way to trade away some 
>> of the more spectacular visual effects to have better interactive 
>> performance.
>> 	I tried to look through the documentation of beta, but there 
>> aren't too much info about performance tuning. The only thing I found is 
>> to set shininess to 0, which helps marginally at best.
>> 	What other tricks can I use to improve interactive performance?  
>> For example, can I tune the smoothness of the spheres? Sometimes my cpu 
>> usage is not even fully 100%, but dragging, rotating and zooming the 
>> image is still very slow.
>> 	It'll really be a shame if I have to revert to the old version 
>> due to performance issue.  There must be a way to balance performance 
>> and effects.
>> 	In a related issue. I also need to render particles between the 
>> spheres in the pack. In the old version, I basically render them as 
>> smaller spheres. But in the new version, there's a mention of point 
>> objects, which seems to be just for that purpose. However, there's not 
>> too much documentation of the point objects. How do I use them? Do they 
>> offer a lighter overhead than the render spheres? Can I give them 
>> colors?
>> 	On the final note, a word about my system: I have a thinkpad 
>> T43, with Pentium M Dothan 1.86MHz, 1GB PC2-4200 memory, ATI X300 mobile 
>> discrete graphics(M22) with 64MB of VRAM, and 60GB 7200rpm disk. It's 
>> not a powerful machine by today's standard, but it runs the old version 
>> of visual just fine. Also, runs other 3D accelerated openGL programs 
>> like googleearth and stellarium just fine(glxgears score, which I know 
>> is not a benchmark, is around 1750 FPS).
>> 	The software environment is an outdated ubuntu(5.04), with 
>> custom compiled 2.6.18 kernel, gcc version 3.3.5, python 2.4, fglrx 
>> proprietary driver 8.42.3(latest).  Numpy 1.0.3, the latest gtkglxtmm I 
>> compiled and installed from source.  If you want to know more, let me 
>> know what more relevant info I can give.
>> 	If there's a simple patch for the stable version 3.2.9 that 
>> enables transparency, I'll be very happy to use that, too. Because 
>> really the stable version satisfies all my need except for 
>> transparencies.
>> 	Thank you all for any hint/help you can give.
>> 								Jiang
>>
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