Re: canvas notes

[Havoc Pennington <hp redhat com>]

On Mon, 2005-08-15 at 20:06 +0200, Soeren Sandmann wrote:
> Havoc Pennington <hp redhat com> writes:
> 
> > So random thoughts.
> 
> A few more random thoughts:
> 

All good stuff, Piccolo and Java3D have some ideas here -

> - Zooming is more than just setting a transformation matrix because
>   the reason you want to zoom is to see more details. So somehow a
>   model needs to be aware of how much detail should be drawn.

Piccolo seems to have this, since it's designed for "zoomable user
interfaces" 

> - Collision detection is worth at least thinking about, or you'll end
>   up with even more O(n^2) algorithms ...

IIRC this is a primitive in Java3D and can trigger behaviors. Seems like
a good hook to provide.

> - Make sure the entire scene isn't redrawn every time something
>   changes. Also make sure the entire scene isn't *traversed* every
>   time something changes.

Java3D seems to have API designed for this, e.g. a bounding sphere you
have to be inside before a behavior will check whether to run, and
requiring you to set a "can change aspect xyz" flag for things you want
to be able to change on the fly (i.e. everything is "const" by default
so Java3D can optimize it). I don't really know what they optimize for
const vs. mutable objects, or what the compile() method does, though.

> - The ability to have translucent 'windows' with a fixed position on
>   the screen. This could be tricky to do while having both good-looking and
>   efficient scrolling. A local compositing manager might be useful for
>   this. How will this work on Windows?

Piccolo docs and examples mentioned a couple different ways to do this,
but I didn't read in detail. I got the vague impression they were doing
it via a hack.

Havoc