[Gambas-user] the math behind full screen rotation

[Kevin Fishburne]

Just when I thought I could see the sun I was cast down again into 
darkness. I've been working on this problem for several days with 
limited success.

I'm trying to implement full screen rotation in an overhead-perspective 
game. The angle of the screen is locked to the angle of the player. If 
the player turns then the screen also turns, meaning the player is 
always facing "up". Here is an example of exactly what I'm trying to do: 
http://www.youtube.com/watch?v=lX_bhygaSy0

These are the variables I'm working with:

orientation ' Player/camera's angle in degrees (Rad(orientation)).
bworkspace  ' Image buffer containing the original non-rotated background.
brotated    ' Image buffer containing the new rotated bworkspace.
cx          ' Camera's x coordinate in bworkspace.
cy          ' Camera's y coordinate in bworkspace.

brotated is larger than bworkspace because the rotation function doesn't 
crop the rotated image:

http://www.eightvirtues.com/sanctimonia/images/bworkspace.png (512x512)
http://www.eightvirtues.com/sanctimonia/images/brotated.png(725x726)

How do I convert the camera coordinates (cx, cy) in bworkspace to the 
equivalent coordinates in brotated? Essentially I need bworkspace to be 
rotated around (cx,cy), but the rotate function only rotates about the 
center of the image. Because of this I think I need some combination of 
rotating (cx,cy) about some point and offseting it as well. Reading my 
own email it sounds simple, but I've tried so many things that I can't 
believe I haven't solved the problem through sheer luck.

-- 
Kevin Fishburne
Eight Virtues
www:http://sales.eightvirtues.com
e-mail:sales at ...1887...
phone: (770) 853-6271