pseudostereo

I'm trying to use scissor_test, glviewport and glscissor to render multiple viewports across multiple displays. It works, but only as long as the viewport size is smaller than my primary display. Once the viewport size = the display size, the multiple viewports stop working; a single viewport fills the whole window, and the window stays this way even after the viewport size is reduced again. The patch has to be closed and reopened for the viewports to start working again.

var vportLoc = [];                //positions/dimensions of viewports

var vportXno;                    //horizontal count of viewports

var vportYno;                    //vertical count of viewports

var vportXpix;                //pixel width of viewports

var vportYpix;                //pixel height of viewports

var vCount;                    //total number of viewports

var mySketch = new JitterObject("jit.gl.sketch","someport");

var myRender = new JitterObject("jit.gl.render","someport");

mySketch.glenable("scissor_test");        //enable multiple viewports

var myWindow = new JitterObject("jit.window","someport");

function viewportSet(xcount,ycount,xwidth,ywidth) {

    for(y=(vportYno-1)*vportYpix;y>=0;y-=vportYpix) {

            vportLoc[c] =[x,y,vportXpix,vportYpix];

            post(c,vportLoc[c],"n");

    myWindow.size = [vportXno*vportXpix,vportYno*vportYpix];

    vCount = clipViewportCount(vportXno*vportYno);

     mySketch.glviewport(0,0,vportXno*vportXpix,vportYno*vportYpi x);        //set to entire window

     mySketch.glscissor(0,0,vportXno*vportXpix,vportYno*vportYpix );    

    myRender.erase();                 // bug?

    myRender.drawswap();            // have to erase+drawswap twice, once before...

    myRender.erase();                 //....once after reset+glclear

        mySketch.glviewport(vportLoc[n]);

        mySketch.glscissor(vportLoc[n]);

         mySketch.glclearcolor(Math.random(),Math.random(),Math.rando m(),1);

//begin multiViewports.js
autowatch = 1;
post ("recompiledn");

var vportLoc = [];				//positions/dimensions of viewports
var vportXno;					//horizontal count of viewports
var vportYno;					//vertical count of viewports
var vportXpix;				//pixel width of viewports
var vportYpix;				//pixel height of viewports
var vCount;					//total number of viewports
var mySketch = new JitterObject("jit.gl.sketch","someport");
var myRender = new JitterObject("jit.gl.render","someport");
mySketch.glenable("scissor_test");		//enable multiple viewports

var myWindow = new JitterObject("jit.window","someport");
myWindow.pos = [0,24];

function viewportSet(xcount,ycount,xwidth,ywidth) {
	vportXno = xcount;
	vportYno = ycount;
	vportXpix = xwidth;
	vportYpix = ywidth;
	c = 0;
	for(y=(vportYno-1)*vportYpix;y>=0;y-=vportYpix) {
		for(x=0;x
			vportLoc[c] =[x,y,vportXpix,vportYpix];
			post(c,vportLoc[c],"n");
			c++;
		}
	}
	myWindow.size = [vportXno*vportXpix,vportYno*vportYpix];
	vCount = clipViewportCount(vportXno*vportYno);
	clear();
	clearColors();
}

function clipViewportCount(slots) {
	slots = Math.max(slots,1);
	slots = Math.min(slots,9);
	return slots;
}

function clear() {
	 mySketch.glviewport(0,0,vportXno*vportXpix,vportYno*vportYpi x);		//set to entire window
	 mySketch.glscissor(0,0,vportXno*vportXpix,vportYno*vportYpix );	

	myRender.erase(); 				// bug?
	myRender.drawswap();			// have to erase+drawswap twice, once before...

	myRender.erase(); 				//....once after reset+glclear
	myRender.drawswap();
}

function clearColors() {
	mySketch.reset();
	for (n=0;n
		mySketch.glviewport(vportLoc[n]);
		mySketch.glscissor(vportLoc[n]);
		 mySketch.glclearcolor(Math.random(),Math.random(),Math.rando m(),1);
		mySketch.glclear();
	}
	myRender.erase(); 
	myRender.drawswap();
}
//end multiViewports.js


jit-gl-multiple-viewports-across-multiple-displays-bug

On Feb 8, 2006, at 11:11 AM, Perry Hoberman wrote:

> I'm trying to use scissor_test, glviewport and glscissor to render 

> multiple viewports across multiple displays. It works, but only as 

> long as the viewport size is smaller than my primary display. Once 

> the viewport size = the display size, the multiple viewports stop 

> working; a single viewport fills the whole window, and the window 

> stays this way even after the viewport size is reduced again. The 

> patch has to be closed and reopened for the viewports to start 

Thanks for the report. I can't reproduce on Mac under 10.4.3 on my 

AluBook with no monitor attached, but I will say that this is not a 

current priority for us to support, and that I'd suggest using two 

> I'm trying to use scissor_test, glviewport and glscissor to render  
> multiple viewports across multiple displays. It works, but only as  
> long as the viewport size is smaller than my primary display. Once  
> the viewport size = the display size, the multiple viewports stop  
> working; a single viewport fills the whole window, and the window  
> stays this way even after the viewport size is reduced again. The  
> patch has to be closed and reopened for the viewports to start  
> working again.

Thanks for the report. I can't reproduce on Mac under 10.4.3 on my  
AluBook with no monitor attached, but I will say that this is not a  
current priority for us to support, and that I'd suggest using two  
windows.

I've already been down the road of using multiple windows. That's slower and much less efficient than scissor_test. It means setting up multiple render contexts, one for each window, which makes it much harder to manage. My scenes often include (for instance) a number of complex models, a couple of jit.gl.nurbs and a bunch of jit.gl.sketch objects - and every single one of those objects has to be duplicated each time for each additional window I'm trying to display.

Whereas if I'm using glscissor and glviewport, I only need a single render context that I can draw to any number of viewports. My example used just two views to demonstrate the bug, but I'm actually trying to build a flexible framework to display any number of views across any number of screens, for CAVE-like immersive displays and the like.

So your response is extremely disappointing. You can't even rustle up an external monitor, at least to verify that the bug is reproducible? I've already put a lot of work into this project, assuming that scissor_test would work as advertised, and I didn't become aware of the bug until I'd already been working on it for weeks, if not months.

On Feb 9, 2006, at 10:32 AM, Perry Hoberman wrote:

> Whereas if I'm using glscissor and glviewport, I only need a single 

> render context that I can draw to any number of viewports. My 

> example used just two views to demonstrate the bug, but I'm 

> actually trying to build a flexible framework to display any number 

> of views across any number of screens, for CAVE-like immersive 

I can't guarantee that it will be supported for more outputs than two 

displays on the same card. This is heavily HW and graphics driver 

dependent, and whether or not the driver supports contexts which span 

multiple graphics cards is something that is out of our hands. So you 

might need to approach with multiple contexts for a greater number of 

As for multiple window performance, for the time being disable the 

sync attribute. This will produce tearing, but it will offer 

additional performance. We will be looking at ways of improving the 

framerate of multiple windows with VBL sync in future versions of 

> So your response is extremely disappointing. You can't even rustle 

> up an external monitor, at least to verify that the bug is 

> reproducible? I've already put a lot of work into this project, 

> assuming that scissor_test would work as advertised, and I didn't 

> become aware of the bug until I'd already been working on it for 

Sorry. We've got lots on our plate, and while I can respect the 

amount of time you've spent on the project, this is a particularly 

advanced feature that therefore takes lower priority over features 

that benefit everyone. This is the unfortunate reality of developing 

applications for more than one specific purpose. Priorities must be 

made. We can investigate this further (as with all bug reports, 

please also provide the specific HW and OS info you are experiencing 

this problem on), but I'm not making any promises to when/if this 

> Whereas if I'm using glscissor and glviewport, I only need a single  
> render context that I can draw to any number of viewports. My  
> example used just two views to demonstrate the bug, but I'm  
> actually trying to build a flexible framework to display any number  
> of views across any number of screens, for CAVE-like immersive  
> displays and the like.

I can't guarantee that it will be supported for more outputs than two  
displays on the same card. This is heavily HW and graphics driver  
dependent, and whether or not the driver supports contexts which span  
multiple graphics cards is something that is out of our hands. So you  
might need to approach with multiple contexts for a greater number of  
outputs anyway.

As for multiple window performance, for the time being disable the  
sync attribute. This will produce tearing, but it will offer  
additional performance. We will be looking at ways of improving the  
framerate of multiple windows with VBL sync in future versions of  
Jitter.

> So your response is extremely disappointing. You can't even rustle  
> up an external monitor, at least to verify that the bug is  
> reproducible? I've already put a lot of work into this project,  
> assuming that scissor_test would work as advertised, and I didn't  
> become aware of the bug until I'd already been working on it for  
> weeks, if not months.

Sorry. We've got lots on our plate, and while I can respect the  
amount of time you've spent on the project, this is a particularly  
advanced feature that therefore takes lower priority over features  
that benefit everyone. This is the unfortunate reality of developing  
applications for more than one specific purpose. Priorities must be  
made. We can investigate this further (as with all bug reports,  
please also provide the specific HW and OS info you are experiencing  
this problem on), but I'm not making any promises to when/if this  
issue will be resolved.

>I can't guarantee that it will be supported for more outputs than two displays on the same card.

OK, but I'd really like to at least get two outputs working with scissors/viewports; at least then I can do polarized stereo with two projectors.

>As for multiple window performance, for the time being disable the sync attribute.

>We can investigate this further (as with all bug reports, please also provide the specific HW and OS info you are experiencing this problem on), but I'm not making any promises to when/if this issue will be resolved.

Tested on both a Powerbook 17" and a G5 desktop, both running Mac OS 10.4.4. Same thing happens on both, whether a second monitor is connected or not: that is, as soon as the viewport size equals or surpasses the monitor size, multiple viewports stop working, even after you reduce the viewport size back down.

Anyway, I understand your position, and I realize that this might not get fixed, but I'd really appreciate any bit of attention you can put towards this.

One small question: any idea if there's any way to turn off the shadows that the active window always casts on the other windows (Mac OS X)?

On 10.02.2006, at 04:27, Perry Hoberman wrote:

> One small question: any idea if there's any way to turn off the 

> shadows that the active window always casts on the other windows 

http://www.unsanity.com/haxies/shadowkiller

> One small question: any idea if there's any way to turn off the  
> shadows that the active window always casts on the other windows  
> (Mac OS X)?

try ShadowKiller: http://www.unsanity.com/haxies/shadowkiller

>try ShadowKiller: http://www.unsanity.com/haxies/shadowkiller

[jit.gl] multiple viewports across multiple displays - bug?