2d ReboundCollide() function

This code has been declared by its author to be Public Domain code.

2d ReboundCollide() function by aab

2004

input the object(image) masses and speeds, and watch them whack each other accordingly. It can be used repeatedly throughout a program without having to repeat the code!

The images (and related co-ordinates) are '1' and '2'

The values 'a' and 'b' are used within the function to demonstrate that it can be used for multiple images and their related co-ordinates (it works via the co-ordinates really)

in order for this to work, the co-ordinates used MUST be global in order for them to be replaced within the function (and preferebly they should be FLOATs.~~What is happenening is that the parameters passed(x1,x2 etc) in this case, temporarily replace xa and
xb, which are then altered within the function, which will then, depending apon the FLAG parameter you input will replace the co-ordinates you input with the shifted ones.

The one thing i resent about this though, is the need for the flag parameter, and for u to have to specify the flag, and edit the 'select' statement within the function to allow different output conditions. ~(For those of you whove used B3d its just like specifying Entitytype, then using 'Countcollisions' for those Entitytypes)

This command in itself should be usefull in using collissions to stop eg:enemies walking through each other, and right through your guy, and for heavy blocks to push(ie:give larger mass# values) and even for ground, by using masses of say 10000 etc. mass of course, (as well as speed) should not fall below 0.0001 (or even 1 in the case of mass), and should not be in excess of 1x(10^7)

how to use
Basically, input the masses and bounce-speeds of the images 'objects', as well as their co-ordinates and handles, and the flag parameter which specifies the co-ordinates to be affected, and you can use this command for multiple collissins throughout a program.
The function returns TRUE if the images do 'rebound collide' and so you could use this in replace for imagesoverlap(,,,,)=true, and it will bounce the images off each other as well.
I dont believe its very magical at all in terms of speed, but it makes ur life a little bit easier.

;Rebound Collide
Graphics 400,300
SetBuffer BackBuffer()
SeedRnd MilliSecs()
AutoMidHandle True


speed1#=1
speed2#=1

image_1=LoadImage( "charsbb\drag.png" )
Global x1#=0
Global y1#=0
image_2=LoadImage( "charsbb\ship.bmp" )
Global x2#=200
Global y2#=150
mass1#=1
mass2#=10
If image_1=0 Or image_2=0 Then RuntimeError "Image Unfound!"

While Not KeyHit(1)
Cls



reboundcollide#(image_1,x1#,y1#,frame1,mass1#,speed1#,image_2,x2#,y2#,frame2,mass2#,speed2#,1)

DrawImage image_1,x1#,y1#
DrawImage image_2,x2#,y2#

If KeyDown(203) x1#=x1#-speed1#
If KeyDown(205) x1#=x1#+speed1#
If KeyDown(200) y1#=y1#-speed1#
If KeyDown(208) y1#=y1#+speed1#

If KeyDown(75) x2#=x2#-speed2#
If KeyDown(77) x2#=x2#+speed2#
If KeyDown(72) y2#=y2#-speed2#
If KeyDown(80) y2#=y2#+speed2#


If KeyDown(16) speed1#=speed1#-0.1
If KeyDown(17) speed1#=speed1#+0.1
If speed#<0.1 speed#=0.1
If speed#>10 speed#=10
Text 0,0,("S1: "+Int(speed1#)+"S2: "+Int(speed2#))
Text 0,10,(Int(x1)+","+Int(y1))
Text 0,20,(Int(x2)+","+Int(y2))

Text 0,50,(reboundcollide#(image_1,x1#,y1#,frame1,mass1#,speed1#,image_2,x2#,y2#,frame2,mass2#,speed2#,1))

VWait:Flip False
Wend
End

Function reboundcollide#(image_a,xa#,ya#,framea,massa#,speeda#,image_b,xb#,yb#,frameb,massb#,speedb#,flag)
	Text 0,30,(Int(xa#)+","+Int(ya#))
	Text 0,40,(Int(xb#)+","+Int(yb#))
	If ImagesCollide(image_a,xa#,ya#,framea,image_b,xb#,yb#,frameb)
		If massa#=0 Or massb#=0 Then RuntimeError "0 Mass? that object can't exist! try 0.00001!"
		If image_a=0 Or image_b=0 Then RuntimeError "Image Handle unparameterised!"
		xa#=xa#+(Sgn(xa#-xb#)*speeda#)/massa#
		xb#=xb#+(Sgn(xb#-xa#)*speedb#)/massb#
		ya#=ya#+(Sgn(ya#-yb#)*speeda#)/massa#
		yb#=yb#+(Sgn(yb#-ya#)*speedb#)/massb#
		Select flag ;this is the part u must annotate for each possible co-ord situation:the FLAG!
			Case 1 x1#=xa# x2#=xb# y1#=ya# y2#=yb#
		End Select
		If Not massa#=0 And massb#=0 Then Return True
	EndIf
	Return False
End Function

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