Re: [Plib-users] Readable user docs for PUI?

[Steve B. <st...@sj...>]

James Frye wrote:
> Hummm... I had been thinking I'd have to re-write most of the drawing 
> code to do 3D drawing instead of 2D - e.g. calling glVertex3f instead of 
> glVertex2i - then changing setPosition & setSize to take 3D coords, adding 
> a setRotation, etc.
>   
Oh - no, no, no!  Certainly not!   PUI uses glVertex2D - but all that 
does is generate a full 3D vertex with Z=0,W=1.  The subsequent 
rotate/translate/perspective transforms operate exactly the same way 
they do for 3D vertices.  You CERTAINLY won't have to do anything like 
that if all you want to do is to simulate a 2D GUI on a virtual 2D 
display placed somewhere out in the 3D world.

Once you have the right transform on the stack, PUI will render in full 
3D just fine.

One thing you MIGHT have problems with is that PUI doesn't clip it's 
underlying primitives to the screen - it lets OpenGL do that.  You'll 
need to set up some user clip planes to fix that properly - but you 
could consider cheating and building your virtual monitor with a nice 
chunky frame that Z-buffers out the PUI widgets that hang off the edges 
of the screen a bit.

Actually - the super-modern way to do this would be to leave PUI 100% 
alone and simply have it render to an RGB texture instead of to the 
screen.  Set up a render-to-texture rendering target - run PUI exactly 
as you would normally - then apply that texture to your virtual computer 
screen.  That would completely take care of the clipping problem and 
allow you to use PUI's standard puDisplay() function.  Then you can 
apply that texture to any polygon(s) in your 3D scene and be utterly 
assured that everything will play nicely.  If you have multiple PUI 
screens in your virtual world then you could also gain some performance 
by only re-rendering the texture for the screen that the user is 
interacting with.  That would be really cool actually - you could easily 
have PUI displayed on translucent screens (like on the movie "Minority 
Report") or whatever.

If you are familiar with the render-to-texture approach then you should 
be able to get this working with just a couple of hour's work and no 
changes whatever to the PUI source.   This would be by far the simplest 
way to do it.
> This is intended to work within an existing VR library (freeVR), so the 
> basic graphics environment gets set up there.  It gives you 3D "wand" 
> coordinates.  I imagine that will involve a bit of work to find what is 
> selected, but it seems simple in principle.
>   
That should make finding the "mouse" coordinates a lot simpler.
>> You can even make PUI draw a software cursor so that your control panels
>> have cursors that move around in perspective and such.
>>     
> Already handled by the VR lib - and of course in a CAVE-like environment 
> it's actually tracking hand or wand position.
>   
OK...But I think I'd leave PUI's software cursor alone because seeing 
that start to track when your virtual hand touches the PUI screen would 
give the end user the confidence that they are indeed driving this 
virtual touch-screen.  But that's obviously something you are better 
placed to figure out than me!

-- Steve.