Re: [Plib-devel] proper plib coding example

[<br...@sa...>]

>
> Yeah - but there can be problems with some applications.  Very often,
> I'll position the camera very carefully so that you aren't intersecting
> adjacent walls, etc.  If you allow the user to (in effect) alter the
> field of view - then other things may go wrong.  In particular, it's
> possible that on-screen iconography will disappear off the top or
> bottom of the screen.

In the case of the viewer app, iconography can only disappear
left/right from the screen, due to the implementation:

Currently, I implemented it so that vertical fov is always fixed,
and horizontal fov is adapted to aspect ratio.

> I think that what most 3D applications truly need is to have the
> user's choice of screen size be used by the application to set only
> the WIDTH of the screen - and as he drags the window around, to
> force the window dimensions such that the pixels remain square *and*
> the horizontal and vertical fields of view are maintained.

I think this is impossible, you could only maintain minimal fov vals,
you cannot fix them and keep aspect ratio the same while user drags.
(unless you disable non-linear window scaling).

In the method I described above, vertical fov is garantueed.
I can imagine an algorithm that will guarantee minimal values
for fov-y and fov-x, will increase fov in one of the two dirs.
As I have it now, fov-x can both decrease and increase from start
setting.

But I agree with you that desired behaviour depends on the app,
although a varying aspect ratio seems bad to me for most cases.
There are also cases where you may want to derive fov-xy directly
from window size, so that increasing windowsize will let you
see more of your model (a ppe window comes to mind).

  bram

PS: The only plib app I could find that keeps aspects correct
was ppe, but this was because ppe uses the opengl widget from
FLTK, which properly recalculates frustums.

> ---------------------------- Steve Baker -------------------------
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