[Gzz] Asko 2002-10-21 (studying)

[Asko Soukka]

9h workday
- ovalbgvob to use mipmap's
- introducing into culling of coordsys problem

I'm still stuck in the beginning of culling coordsys, because I just can't 
understand libcoords as a whole. Maybe some of the principles, but the 
code in Coords.cxx looks still alien to me.

So, I tried to figure out how to continue. I understood that after 
building interface I should have two coordinate transformations 
available. AFAIK my problem is to detect (in culledCoordsys' 
shouldBeDrawn() method) do the unit squares of those two 
coordinate system intersect. Detecting intersections is not trivial 
because after transformation the unit squares might be quite distorted.

What are those "two coordinate transformations"? Can I assume them as
Renderable.Object => Window.Object and
Clip.Object => Window.Object?
Or can I more generally assume that 2D intersection detection is enough? 
At least in Window.object it should be?

I'm been thinking about finding convex hulls for those distorted unit 
squares. One convex hull for both at beginning, but if it's too 
inaccurate, maybe more (by splitting the distorted unit square). 
After finding convexes there should be fast intersection detection 
algorithms for 2D convex polygons. I don't know them yet or haven't ever 
implemented one, but I believe they exists O:-)

The amount of convexes per unit square could probably be parallel to what 
Tuomas has said about "different algorithms for different cases".

Thinking this tomorrow...

-- 
Asko Soukka     | Taitoniekantie 9 A 603 | address@hidden
+358-40-8235947 | FIN-40740 JYVÄSKYLÄ    | http://www.iki.fi/asko.soukka/