Hail, Knight! (This needs to be the new greeting for us. Smile )

I'd like to know about vector mathematics from the ground up and how I would implement collision detection using the Separating Axis Theorum. In Lua is preferred but, in theory is cool too.


Reminder for Kerm to change my title from Power User to Phantom of Vandalia.
Well, there are some useful tutorials online. Do you have any questions specifically?
I'd like to know how to get the vectors or vertices from an image and check that image for collisions using the Separating Axis Theorum.
Raylin wrote:
vectors or vertices from an image

Sounds like a misapplication of SAT. Working from a raster image, you either need to treat it as a large poly with a vertex at each external pixel, or have a separate structure tracking its hitbox. Either way, it's pretty clunky.

The usual way to check collision between arbitrary sprites (which I assume is what you intend to do) is seeing if they overlap at all when drawn, AFAIK.
The Tari is correct regarding normal hit detection. You generally want to check for intersection with the less-numerous objects when drawing the more-numerous objects. For example, if you have tons of bullets, you can check for overlap with ships during the bullet rendering loop. Alternatively, you can do pixel-based detection: if any pixel inside your ship's sprite (or mask) is colored, you've been hit. If you want the most trivial way to check coordinate overlap (ASM?) here's an example from Doors CS:

;----------Hot spot detection-----------
;inputs: b,c (first x and y cor)
;        d,e (last x and y cor)
;        h,l (current x,y)
;output: "z" flag [either true (set) or false (reset)]

   ld a,h
   cp b
   jr c,hno_detect
   cp d
   jr nc,hno_detect
   ld a,l
   cp c
   jr c,hno_detect
   cp e
   jr nc,hno_detect
   xor a
   or a
   xor a
   cp 1
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