Re: [Chromium-users] Selecting what to tilesort?

[Brian P. <bri...@tu...>]

Paul Melis wrote:
> Hi Brian,
> 
> Brian Paul wrote:
> 
>> Paul Melis wrote:
>>
>>> Hello,
>>> I'm wondering if the following is possible with Chromium (I've 
>>> already got a bit of success, but no glory yet):
>>>
>>> I have an application, a molecular visualisation package, that I'd 
>>> like to run on a 3-screen cylindrical projection setup. I've got a 
>>> chromium configuration to work that does the non-planar tiling. But 
>>> since the application was meant as a normal desktop application, the 
>>> opengl window not only shows molecular structures and stuff in 3D, 
>>> but also contains GUI elements (buttons, text, a command input line, 
>>> etc) drawn in opengl. I don't think these elements, that are probably 
>>> rendered in ortho2d mode, can be made to display correctly on the 
>>> cylindrical screen, nor is it that important. I'd like to "cut out" 
>>> that part of the viewport where the molecules are visible and only 
>>> distribute the geometry visible in that part. Is there a way to set 
>>> up chromium to get this done?
>>
>>
>>
>> You might try writing a new SPU that examined the matrix operations 
>> (glOrtho, glFrustum(), etc) to determine whether the 2D or 3D stuff 
>> was being drawn, then no-op rendering commands as needed.
> 
> 
> I indeed took this route after your suggestion, writing a "filter3d" SPU 
> and it seems to work fine in identifying the right parts to keep and 
> what to throw away. But I'm having trouble with one aspect of this 
> approach.
> 
> As the GUI elements drawn provide functions that are still usable and 
> some even unavailable in the separate GUI app made in Tcl/Tk the 
> application is using, I'd like to keep the GUI elements on the master 
> node where the app is controlled. In effect letting the opengl stream 
> pass through unmodified.
> 
> So my basic idea is:
> 1. run the visualisation app on a master node, where it runs as usual in 
> the eyes of a user. the user can interact using mouse/keyboard and also 
> use the GUI elements drawn in opengl.
> 2. run 3 render nodes that each display a part of the 3D geometry, but 
> not any of the GUI elements
> 
> Chromium is working behind the scenes on the master node intercepting 
> the opengl stream and distributing it to the 3 nodes using the tilesort 
> SPU. The problem is where to put my filter3d SPU.
> If I try to attach it on the slave side, once for each of the 3 nodes, 
> it doesn't seem to have an effect. Could it be that opengl commands such 
> as Viewport and MatrixMode are influenced by the tile-sorting? Perhaps 
> an Ortho call is left out (as that is what the filter3d SPU basically 
> looks for)?

Yes, that may be the case.  The tilesort SPU and crservers do 
manipulate the viewport and projection.


> If I put filter3d before the tilesort SPU then the distributed scene is 
> correct, none of the GUI elements are left in and I only get the "pure 
> 3D" geometry.
> But then I don't have a non-filtered display on the master node anymore :-/
> 
> It feels like I need to split the opengl stream somewhere and send a 
> filtered one to the render nodes and an unfiltered one to the master. Is 
> this possible in an efficient way?

Other people have tried this, with mixed results, by adding another 
tilesort SPU to the mix which uses two identical tiles.


> In the docs it is mentioned that Chromium uses a graph-structure in 
> defining the connections between nodes, but I assume that with SPUs you 
> can only create a chain and not a split?

The only way to split today is with the tilesort SPU.

-Brian