Triangle Collision Check - GameCreators Forum

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Ashingda 27

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Joined: 15th Feb 2008

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Posted: 24th Mar 2010 01:08 Edited at: 3rd Sep 2012 02:09

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I was messing around with my isometric tile map and stumbled onto this. This may only be useful in 2d tile-based game however.

+ Code Snippet

sync on
sync rate 0

 
do
	gosub Test
	sync
	cls
loop

	Test:
		gosub Display
		gosub Control
	return

		Display:
			ink rgb(255,255,255),0
			box 100,100,200,200
			ink rgb(255,0,0),0
			line 100,100,200,100
			line 100,100,100,200
			line 100,200,200,100

			ink rgb(200,200,255),0
			text 0,0,"Collision: "+str$(Collision)
		return

		Control:
			Collision = 0
			if CheckArea(100,100,200,200)
				mx = mousex()-100
				my = mousey()-100
				if mx+my < 100 then Collision = 1
			endif
		return



Function CheckArea(x1,y1,x2,y2)
	mx = mousex()
	my = mousey()
	if mx > x1 and mx < x2 and my > y1 and my < y2 then value = 1 else value = 0
EndFunction value

The example shows a rough collision check of the top left corner of the box. It is also possible for all the other corners and you can adjust the length of a side.

+ Code Snippet

sync on
sync rate 0


do
	gosub Test
	sync
	cls
loop

	Test:
		gosub Display
		gosub Control
	return

		Display:
			ink rgb(255,255,255),0
			box 100,100,200,200
			ink rgb(255,0,0),0
			line 100,100,200,100
			line 100,100,100,150
			line 100,150,200,100

			ink rgb(200,200,255),0
			text 0,0,"Collision: "+str$(Collision)
		return

		Control:
			Collision = 0
			if CheckArea(100,100,200,200)
				mx = mousex()-100
				my = mousey()-100
				if mx+(my*2) < 100 then Collision = 1
			endif
		return



Function CheckArea(x1,y1,x2,y2)
	mx = mousex()
	my = mousey()
	if mx > x1 and mx < x2 and my > y1 and my < y2 then value = 1 else value = 0
EndFunction value

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chafari

Valued Member

17

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Joined: 2nd May 2006

Location: Canary Islands

Posted: 24th Mar 2010 01:48

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It works!!, and I think this method can be translated to 3D just using x,z as the x,y of mouse, but now a day, there are good methods for 3D collision check, any way...good job !!.

Cheers!

I'm not a grumpy grandpa

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Libervurto

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Joined: 30th Jun 2006

Location: On Toast

Posted: 25th Mar 2010 17:28 Edited at: 25th Mar 2010 17:31

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Nice.
I've overhauled your code.

I couldn't work out what the (mx-100) was for so I took it out and put in my own code for checking the triangle.
I've put everything in variables so it is very tweak-able.

rem Program Name: Triangle Collision
rem Author: Ashingda27
rem Date: 24/03/2010
rem ==================
rem Edited by OBese87 - 25/03/2010
rem ==================
sync rate 0
sync on

rem Constants
boxcol = rgb(255,255,255)
tricol = rgb(255,0,0)
txtcol = rgb(200,200,255)
boxax = 100
boxbx = 400
boxay = 100
boxby = 200
grad# = (boxby-boxay)/(boxbx-boxax+.0)

rem === MAIN ===
do
  gosub Test
  sync:cls
loop

rem === SUBROUTINES ===
CheckCollision:
  if CheckArea(boxax,boxay,boxbx,boxby)
    BoxCollision = 1

mx = mousex()
    my = mousey()
    rem We are already inside the box so we just need to check if we are above the gradient.
    if (my-boxay) < (mx-boxax)*grad# then TriCollision = 1 else TriCollision = 0
  else
    BoxCollision = 0
    TriCollision = 0
  endif
return
`//
Display:
  ink boxcol,0
  box boxax,boxay,boxbx,boxby
  ink tricol,0
  line boxax,boxay,boxbx,boxay
  line boxbx,boxay,boxbx,boxby
  line boxax,boxay,boxbx,boxby
  ink txtcol,0
  print "Gradient: "; grad#
  print "Triangle Collision: "; TriCollision
  print "Box Collision: "; BoxCollision
return
`//
Test:
  gosub CheckCollision
  gosub Display
return
`//

rem === FUNCTIONS ===
Function CheckArea(x1,y1,x2,y2)
   mx = mousex()
   my = mousey()
   if mx > x1 and mx < x2 and my > y1 and my < y2 then value = 1 else value = 0
EndFunction value

+ Code Snippet

rem Program Name: Triangle Collision
rem Author: Ashingda27
rem Date: 24/03/2010
rem ==================
rem Edited by OBese87 - 25/03/2010
rem ==================
sync rate 0
sync on

rem Constants
boxcol = rgb(255,255,255)
tricol = rgb(255,0,0)
txtcol = rgb(200,200,255)
boxax = 100
boxbx = 400
boxay = 100
boxby = 200
grad# = (boxby-boxay)/(boxbx-boxax+.0)

rem === MAIN ===
do
  gosub Test
  sync:cls
loop

rem === SUBROUTINES ===
CheckCollision:
  if CheckArea(boxax,boxay,boxbx,boxby)
    BoxCollision = 1

    mx = mousex()
    my = mousey()
    rem We are already inside the box so we just need to check if we are above the gradient.
    if (my-boxay) < (mx-boxax)*grad# then TriCollision = 1 else TriCollision = 0
  else
    BoxCollision = 0
    TriCollision = 0
  endif
return
`//
Display:
  ink boxcol,0
  box boxax,boxay,boxbx,boxby
  ink tricol,0
  line boxax,boxay,boxbx,boxay
  line boxbx,boxay,boxbx,boxby
  line boxax,boxay,boxbx,boxby
  ink txtcol,0
  print "Gradient: "; grad#
  print "Triangle Collision: "; TriCollision
  print "Box Collision: "; BoxCollision
return
`//
Test:
  gosub CheckCollision
  gosub Display
return
`//

rem === FUNCTIONS ===
Function CheckArea(x1,y1,x2,y2)
   mx = mousex()
   my = mousey()
   if mx > x1 and mx < x2 and my > y1 and my < y2 then value = 1 else value = 0
EndFunction value

"With games, we create these elaborate worlds in our minds, and the computer is there to do the bookkeeping." - Will Wright

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Ashingda 27

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Joined: 15th Feb 2008

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Posted: 25th Mar 2010 19:56 Edited at: 25th Mar 2010 19:57

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Wow that's nice I like it, a lot easier to use.

that mx-100 was because the start of the box is (100,100).