Re: [sgl-dev] SGL and TuxFleet

[Alexander R. <a_r...@in...>]

Hi,

Scott McMillan wrote:
> 
> Alexander Rawass wrote:
> >
> > Ok, see the files in attachment:
> >
> > When I start tuxfleet now, I can see the spaceships rotating in space,
> > they are also correctly positioned and scaled
> > But the fov isn't set correctly, I draw with openGL boxes around the
> > spaceships, and the boxes are just 'near' the place where the ships get
> > draw.
> 
> You would have to be a bit more precise about what you mean by 'near'.
> 
> Besides how do you draw boxes around them?  Do you draw 2D boxes on the
> near clip plane or do you put something in the scene graph?

I draw the 2D boxes after setting openGL to '2D' with 
    glOrtho(0.0 , winx , winy,  0.0 ,-1,1);

I calculate the 2D coordinates of the boxes from the 3D coordinates
without openGL and then do some GL_LINES in 2D.

> > spaceships, and the boxes are just 'near' the place where the ships get

I mean:

The FOV of the 3D models getting drawn with SGL and the FOV that the
2D-boxes use to get drawn are not the same, so you can see the ships at
a position and the boxes are near (in terms of mm on the monitor) the
ships, and if you move or rotate it gets worse - it feels as if the FOV
of the ships would be greater than the FOV of the 2D boxes.

> > I tried a closer look at buildFrustum and applied some changes, but
> > didn't succeed doing anything better.
> > I suspect that buildFrustum is somehow not correct - when I increase the
> > fov in TuxFleet by typing < > , or ., that doesn't work correctly - if I
> > steadily increase fov_y by 1 for example, the fov gets wider - mostly -
> > but at some values the ships simply vanish until I increase the fov
> > further.
> 
> I am 99% sure my build frustum code is correct.  Some of the equations
> were taken directly from Mesa.  And besides, it has been heavily

Yes, I've seen that.

> tested by PowerScene.  You do realize that you need to send the FOV
> in radians to the buildFrustum command?

Yes - but it took me some time until I did :-(

> When I sent you code once I know I initialized the fov_x and fov_y
> values incorrectly:
> 
>         fov_x(60.0*180.0/M_PI),
>         fov_y(45.0*180.0/M_PI),
> 
> It should have read
> 
>         fov_x(60.0*M_PI/180.0),
>         fov_y(45.0*M_PI/180.0),

Shouldn't matter, since I set it.

> If you choose to set fov_y to -1.0 you must make sure that win_x and
> win_y are the same size as the window or the frustum won't work.
> 
> > There's also a lighting problem:
> >
> > All ships are draw with much too  much light - so much light that you
> > can't even see the contoures of the ships, changing the values in
> > TuxFleet's configuration file has no effect.
>
> This is might be a problem with how you are scaling the models.  If
> there
> is a bug in SGL it might not be renormalizing the normals (I doubt it
> though).

Ok, coming back to scaling (exept for the lighting effect the models are
correctly scaled) :

The matrix I pass to FleetSceneObject::setTransMatrix is correctly
scaled, the direction vectors in the matrix are scaled and are
orthogonal but not orthonormal.

Should I do the scaling differently?

> Alternatively, it could be a bug with Mesa, which PLIB doesn't exercise
> although I couldn't imagine what off-hand.

It's the Nvidia-GL drivers.

> Or, it could be a difference between the sglLight code and the built-in
> PLIB lights.
> 
> Without being able to run your code, I couldn't begin to figure this
> out.  I am not sure I have time right now.

Don't matter, it has time - and in between, I'll try to work it out for
myself.


Alex


-- 
                   Alexander Rawass
          Email: ale...@us...
     Project Homepage: http://tuxfleet.sourceforge.net
...but some day you'll be a STAR in somebody else's SKY...