Re: [pygame] Pixel Perfect collision suggestion.

[John Eriksson <john@xxxxxxxxxxxx>]

You are right! Your algorithm is actually a bit faster :-D
At first it seems you've added some extra loops but when looking closer
I saw that you're code check edges first instead of roaming thourgh the
pixels top to bottom.

Well done! 

I would like to include your algorithm in the PixelPerfect example if
its ok with you?

Best Regards
/John

tis 2007-01-30 klockan 20:28 +0530 skrev V. Karthik Kumar:
> Hi John,
> 
> The code that was given is a modified version of PixelPerfect. Please 
> look into it. :)
> 
> I noticed that the code that i posted is probably doing redundant 
> comparisons for odd pixel width/height collision rectangles (when 
> reduced to 1 x h ow w x 1 ), which I'll modify.
> 
> Regards
> 
> John Eriksson wrote:
> > Hi,
> >
> > If you're looking for a pixel perfect collision detection algorithm,
> > there is a project at pygame which contains an even faster one.
> >
> > PixelPerfect - http://www.pygame.org/projects/9/207/
> >
> > It also contains some replacements methods for spritecollide,
> > groupcollide and spritecollideany and an example to show how to use it.
> >
> > The algorithm was used in one of the Second Pyweek Challenge winners! 
> >
> > Trip on the Funny Boat - http://www.pygame.org/projects/20/235/
> >
> > Best Regards
> > /John Eriksson
> >
> >   
> 
> > tis 2007-01-30 klockan 06:30 -0800 skrev Kamilche:
> >   
> >> V. Karthik Kumar wrote:
> >>     
> >>> I happened to read the changes list a day ago. I saw the code, I thought 
> >>> that this change might help detect regular pp cols faster.
> >>>
> >>> This version keeps checking pixels from the outer rectangle of the 
> >>> colliding area to the inner. It works considerably faster when objects 
> >>> are regular and convex, which is often the case.
> >>>
> >>> This isn't a patch as such, I'd recommend people try it out and report 
> >>> the results and then decide.
> >>>
> >>> Regards,
> >>> Karthik
> >>>
> >>>
> >>> ------------------------------------------------------------------------
> >>>
> >>> def pp_collide(obj1,obj2):
> >>>     """If the function finds a collision it will return True
> >>>     if not it will return False.
> >>>     """
> >>>     rect1, rect2, hm1, hm2 = obj1.rect, obj2.rect, obj1.hitmask, obj2.hitmask
> >>>     if not rect1.colliderect(rect2):
> >>>         return False
> >>>     rect = rect1.clip(rect2)
> >>>
> >>>     w, h, x1, y1, x2, y2 = rect.width, rect.height, rect.x-rect1.x, rect.y-rect1.y, rect.x-rect2.x, rect.y-rect2.y
> >>>
> >>>     while w > 0 and h > 0:
> >>> 	for x in range(w):
> >>> 		if hm1[x1+x][y1] and hm2[x2+x][y2]:
> >>> 			return True
> >>> 		if hm1[x1+x][y1+h-1] and hm2[x2+x][y2+h-1]:
> >>> 			return True
> >>> 	for y in range(1, h-1):
> >>> 		if hm1[x1][y1+y] and hm2[x2][y2+y]:
> >>> 			return True
> >>> 		if hm1[x1+w-1][y1+y] and hm2[x2+w-1][y2+y]:
> >>> 			return True
> >>> 	w, h, x1, y1, x2, y2 = w-2, h-2, x1+1, y1+1, x2+1, y2+1
> >>>     return False
> >>>       
> >> Is it faster than pygame's builtin rect.collidepoint method?
> >>     
> >
> >
> >