Re: [osg-users] trouble with flattening static transforms
Hi Terry, A glatten static transforms that have duplicates shared subgraphs would be a useful addition to osgUtil::Optimizer so if you are willing to tidy up and submit it'd be appreciated. Cheers, Robert. On Thu, Jan 31, 2008 at 9:56 PM, Terry Welsh [EMAIL PROTECTED] wrote: I went ahead and wrote a visitor that really does remove all static transforms. If nodes underneath transforms have multiple parents, it makes copies so that each child subgraph can be properly transformed. On my big test case, I remove 911 out of 911 transforms, my model takes up 10x the memory, and it runs 25-30% faster. It's a good tradeoff for the app I'm working on. There's probably plenty of refinement necessary for corner cases since I have only tested with 2 models, but if this sounds worthwhile to anyone else I can fix up a few things and submit it. - Terry Message: 16 Date: Tue, 29 Jan 2008 19:28:24 + From: Robert Osfield [EMAIL PROTECTED] Subject: Re: [osg-users] trouble with flattening static transforms To: OpenSceneGraph Users osg-users@lists.openscenegraph.org Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1 Hi Terry, You can't flatten a static transform when anything it its subgraph is shared with other transforms, if you do flatten it the the object is the trying to be in two places at one time, something it can't do, what happens to these objects is undefined, in fact quite rightly disallowed until you hacked away at it... The only way to flatten these objects shared beneath multiple transforms is to duplicate the subgraph so that each transform has its own unique subgraph. This itself has its own penalties in terms of performance. Robert. On Jan 29, 2008 7:14 PM, Terry Welsh [EMAIL PROTECTED] wrote: So I have a big city database that I built in Creator with lots of external models loaded under transform nodes. I assumed that Optimizer could flatten this out for me with FLATTEN_STATIC_TRANSFORMS. Unfortunately, I only end up flattening 35 out of 911 transforms. Tracing through the code, I find that line 804 of Optimizer.cpp is where things go bad for me: if (_firstMatrix!=matrix) _moreThanOneMatrixRequired=true; This line rejects most of my flattening because later on _moreThanOneMatrixRequired seems to be used to decide whether or not to flatten. If I comment this line out, then all but the first instance of each model disappears from my scene. Understanding all the logic in Optimizer.cpp could take me a long time. Is there some fundamental reason why having more than one matrix makes it impossible to flatten a model, or is this just incomplete code that I could extend to give me a more thorough flattening? Any tips on how to try and extend it would be great too -- Terry Welsh - mogumbo 'at' gmail.com www.reallyslick.com | www.mogumbo.com ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] trouble with flattening static transforms
Hi Terry, You can't flatten a static transform when anything it its subgraph is shared with other transforms, if you do flatten it the the object is the trying to be in two places at one time, something it can't do, what happens to these objects is undefined, in fact quite rightly disallowed until you hacked away at it... The only way to flatten these objects shared beneath multiple transforms is to duplicate the subgraph so that each transform has its own unique subgraph. This itself has its own penalties in terms of performance. Robert. On Jan 29, 2008 7:14 PM, Terry Welsh [EMAIL PROTECTED] wrote: So I have a big city database that I built in Creator with lots of external models loaded under transform nodes. I assumed that Optimizer could flatten this out for me with FLATTEN_STATIC_TRANSFORMS. Unfortunately, I only end up flattening 35 out of 911 transforms. Tracing through the code, I find that line 804 of Optimizer.cpp is where things go bad for me: if (_firstMatrix!=matrix) _moreThanOneMatrixRequired=true; This line rejects most of my flattening because later on _moreThanOneMatrixRequired seems to be used to decide whether or not to flatten. If I comment this line out, then all but the first instance of each model disappears from my scene. Understanding all the logic in Optimizer.cpp could take me a long time. Is there some fundamental reason why having more than one matrix makes it impossible to flatten a model, or is this just incomplete code that I could extend to give me a more thorough flattening? Any tips on how to try and extend it would be great too -- Terry Welsh - mogumbo 'at' gmail.com www.reallyslick.com | www.mogumbo.com ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] trouble with flattening static transforms
If you have a transform tree, with the following: A: translate (0, 10, 0) | ---B: translate( 0, 5, 0 ) | | | --- Model 1 | ---C: translate( 0, 20, 0 ) | --- Model 2 Then A cannot be flatten with B and C, because B != C. If A, B, and C were flattened into a single transform, then Model 1 or Model 2 would end up in the wrong place. If you really want them flattened, then you could translate all vertices in Model 2's geometry by 15 along the Y to account for the difference in C. However, doing this in general could introduce numeric error if your models span a wide area. It's sort of a balancing act, where you try to group nearby models, modify their geometries to share a common origin, and apply a single transform to all of them. However, because that action requires knowledge of the lower scene graph, an optimizer can't do it for you. Also, this wouldn't work with paged children without saving out the modified geometry, and you'd have to apply different techniques to make it work on non-geometry drawables. Hope that helps, Chase -Original Message- From: [EMAIL PROTECTED] [mailto:osg-users- [EMAIL PROTECTED] On Behalf Of Terry Welsh Sent: Tuesday, January 29, 2008 11:14 AM To: osg-users@lists.openscenegraph.org Subject: [osg-users] trouble with flattening static transforms So I have a big city database that I built in Creator with lots of external models loaded under transform nodes. I assumed that Optimizer could flatten this out for me with FLATTEN_STATIC_TRANSFORMS. Unfortunately, I only end up flattening 35 out of 911 transforms. Tracing through the code, I find that line 804 of Optimizer.cpp is where things go bad for me: if (_firstMatrix!=matrix) _moreThanOneMatrixRequired=true; This line rejects most of my flattening because later on _moreThanOneMatrixRequired seems to be used to decide whether or not to flatten. If I comment this line out, then all but the first instance of each model disappears from my scene. Understanding all the logic in Optimizer.cpp could take me a long time. Is there some fundamental reason why having more than one matrix makes it impossible to flatten a model, or is this just incomplete code that I could extend to give me a more thorough flattening? Any tips on how to try and extend it would be great too -- Terry Welsh - mogumbo 'at' gmail.com www.reallyslick.com | www.mogumbo.com ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
