[OSM-dev] Some help with proj.4

Robert Scott lists at riscott.ukfsn.org
Wed Apr 11 15:15:46 BST 2007


Sorry to reopen a thread - haven't been keeping up with my email lately.

On Saturday 07 April 2007 22:54, Stefan de Konink wrote:
> > My target is an embedded system I like to use in a car. For now I use
> > OpenGL as drawing engine while development because I know it well. But
> > perhaps I'll later change the graphic subsystem because there's
> > probably no 3D chip on my hardware.
>
> I'm in exactly the same situation. Target is a free car routing thingie.
> Why I mentioned cairo is simple, there are virtually no embedded 3D
> systems.
>
> > You could help me to get started with my application. Perhaps we've the
> > same target and could work together in future.
>
> I guess we are. So basically I guess we should start rendering some
> elementairy shapes. Don't forget, if we get it to work in Cairo, we have
> an OpenGL backend. Now the downside to that is; You cannot easy change a
> map from flat to birdview. And that kind of stuff need to be done
> manually.

The major problem you're going to face here is you'll find yourself without an 
FPU. Soft FPUs really won't cut it when your principal computational task is 
throwing floats around. Cairo is very float-y code.

It's a factor you'll have to take into account from the start when designing 
your application. Developing it as desktop software and just dropping in a 
new drawing toolkit at the end will probably not solve your problems.

To this end, OpenGL ES makes heavy use of fixed point maths. However the state 
of Free OpenGL ES implementations ain't good from what I can tell.


robert.




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