Selection - done on server or client?

Selection - done on server or client?

Post by Erich Ede » Tue, 10 Dec 1996 04:00:00



Hi,

I wonder where the selection in Open GL is actually done. On the server
or client side? I'm asking because I don't want to use a big selection
buffer and evaluate it when all the objects have been draw. I'd rather
like to enter selection mode, draw one of the objects, switch back to
render mode, test if there was a hit, and do the same with all other
objects. If the selection test is done locally, all these mode switches
shouldn't decrease the performance too much. (Please, correct me if I'm
wrong.) However if it's a remote server that does the calculations,
there must be an unacceptable round-trip for each test.

I cannot check this out, because I'm using Mesa where everything is done
locally, but I wan't to be compatible with real client-server
implementions. Can anybody shed some light on this?

Thanks,
Erich

 
 
 

Selection - done on server or client?

Post by Allen Ak » Tue, 10 Dec 1996 04:00:00



|
| I wonder where the selection in Open GL is actually done. On the server
| or client side?

It varies from machine to machine, so if portability is important for
your application, you might want to perform selection in batches.

Allen

 
 
 

Selection - done on server or client?

Post by Andy Vespe » Thu, 12 Dec 1996 04:00:00



> I wonder where the selection in Open GL is actually done. On the server
> or client side?

Server side.

Quote:>I'm asking because I don't want to use a big selection
> buffer and evaluate it when all the objects have been draw. I'd rather
> like to enter selection mode, draw one of the objects, switch back to
> render mode, test if there was a hit, and do the same with all other
> objects. If the selection test is done locally, all these mode switches
> shouldn't decrease the performance too much. (Please, correct me if I'm
> wrong.) However if it's a remote server that does the calculations,
> there must be an unacceptable round-trip for each test.

Yes, on some implementations this will have unacceptable performance.

In addition, if you drop out of the selection loop early, how will
you ever find out if the first object that gets a selection hit
is the right one to choose? You might get an object that is in back
of ten other objects that would also get selection hits; the user
might wonder why the program insists on selecting a hidden pyramid
when the mouse pointer is clearly on top of that teapot.

Of course, you may be sorting your objects from front to back, but that
does not always give the right results.
--
Andy V (A Digital spoke, not a Digital Spokesperson)

 
 
 

1. Vector Graphics in Client-Server Computing...

Does anyone know of current work that's going on
in the field of Vector Graphics and Vector Graphics
file formats.
I'm particularly interested in work done in the
Client-Server domain.

The application I am involved with is development work
for Digital Television.

Practical examples would be really good too, for example
if anyone knows of a Web Browser plug-in that supports
XYZ Vector graphics format, and how it works, that would
be greatly appreciated.

Many Thanks,

Ted.

--
Ted O'Neill
British Broadcasting Corporation
Research and Development



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