How do I do 2D circle collision?

Author

Message

Null Freq

21

Years of Service

User Offline

Joined: 16th Dec 2003

Location:

Posted: 6th Jan 2004 09:55 Edited at: 6th Jan 2004 09:58

Link

Hello,

I have been trying to figure this out for the past hour.. I want to make the "player" circle stop at the "radius" of the other circle on the screen but still be able to move around the other circle.. I know this is probly very easy to do but I've only been using DBC for about 4 months now and Its one big learning experince!

Thanks to all who help!

+ Code Snippet

REM ***PLAYER CORDINATES AND INFO
xpos#=320
ypos#=240
radius#=10
name$="player"
REM ***PLAYER CORDINATES AND INFO



REM ***ENEMIE CORDINATES AND INFO
enemy_xpos#=420
enemy_ypos#=260
enemy_radius#=10
enemy_name$="enemy"
REM ***ENEMIE CORDINATES AND INFO


REM ***SET SYNC
SYNC ON
SYNC RATE 40
REM ***SET SYNC


REM ***MAIN LOOP
DO

   GOSUB movement
   GOSUB collision
   GOSUB enemy
   
   SYNC
   CLS

LOOP
REM ***MAIN LOOP


movement:
   IF RIGHTKEY()=1 THEN xpos#=xpos#+5
   IF LEFTKEY()=1  THEN xpos#=xpos#-5
   IF UPKEY()=1    THEN ypos#=ypos#-5
   IF DOWNKEY()=1  THEN ypos#=ypos#+5
   TEXT xpos#-20,ypos#-30,name$
   circle xpos#,ypos#,radius#
RETURN


collision:
   IF xpos# < 10  THEN xpos#=10
   IF xpos# > 630 THEN xpos#=630
   IF ypos# < 10  THEN ypos#=10
   IF ypos# > 470 THEN ypos#=470
RETURN

enemy:
   circle enemy_xpos#,enemy_ypos#,enemy_radius#
RETURN

~Falling Down~

Back to top

Profile PM Email Website

Phaelax

DBPro Master

22

Years of Service

User Offline

Joined: 16th Apr 2003

Location: Metropia

Posted: 6th Jan 2004 10:37

Link

+ Code Snippet

P = player
C = colliding circle

if dist#(px,py,cx,cy) <= pRadius+cRadius then HIT!


function dist#(x1,y1,x2,y2)
  d# = sqrt((x1-x2)^2 + (y1-y2)^2)
endfunction d#

Back to top

Profile PM Email Website

Jess T

Retired Moderator

21

Years of Service

User Offline

Joined: 20th Sep 2003

Location: Over There... Kablam!

Posted: 6th Jan 2004 10:45 Edited at: 6th Jan 2004 10:46

Link

Use the distance formula to check their radii.

The dist. formula is:

dist = Sqrt((y2 - y1)^2 + (x2 - x1)^2)

where x1,y1 is the center of one of the circles, and x2,y2 is the center of the other circle.

Then check the distance.
If it is greater than r1 + r2 ( r1 and r1 being the radii of the circles ) Then no collision has occured.
If it is less then or equal to r1 + r2 then collision is occuring and you need to adjust it appropriatly.

a function might do:

+ Code Snippet

Function _inzone(x1,y1,r1,x2,y2,r2)


   inzone = 0
   dist = Sqrt((y2 - y1)^2 + (x2 - x1)^2)

   If dist <= r1 + r2 Then inzone = 1


EndFunction inzone

Then, to use it, in the loop, put:

+ Code Snippet

If _inzone(x1,y1,r1,x2,y2,r2) = 1 Then do whatever

But, replace the x1,y1,r1,x2,y2,r2 with the appropriate values.

Hope I Helped...

[EDIT] Whoops, Phaelax beet me to it [/EDIT]

Team EOD :: Programmer/Logical Engineer/All-Round Nice Guy

Back to top

Profile PM Email Website

Null Freq

21

Years of Service

User Offline

Joined: 16th Dec 2003

Location:

Posted: 6th Jan 2004 11:42 Edited at: 6th Jan 2004 11:43

Link

Thank you for your help but I am not very sure on how to use functions yet.

Is there a simpler way to do this? I didnt make my code above so it could be easily readable or useable thats about as advanced as my current DBC knowledge is.

Thank you again

~Falling Down~

Back to top

Profile PM Email Website

Jess T

Retired Moderator

21

Years of Service

User Offline

Joined: 20th Sep 2003

Location: Over There... Kablam!

Posted: 6th Jan 2004 12:00

Link

Yeah, there's an easier way...

Just use a gosub.:

+ Code Snippet

inzone:
   inzone = 0
   dist = Sqrt((y2 - y1)^2 + (x2 - x1)^2)

   If dist <= r1 + r2 Then inzone = 1
Return

And just before you call the Gosub, set the values, ie, x1 = whatever etc. etc.

Then, after the gosub check to see if inzone = 1, ie, If inzone = 1 Then whatever.

Hope I Helped...

Team EOD :: Programmer/Logical Engineer/All-Round Nice Guy

Back to top

Profile PM Email Website

Sorry your browser is not supported!

DarkBASIC Discussion / How do I do 2D circle collision?