TheGameCreators - CodeBase - Gravity and Bounce

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Category: Math / Physics

Version: 1.0

Information

Uploaded: 22nd Jan 2005 05:21

Modified: 1st Jan 1970 01:00

Author: RiiDii

Summary

Gravity and Bounce functions/engine.

Full Description

Use the left and right arrow keys to rotate the camera.<br /> <br /> Play around with the physics and number of balls a bit to see how it handles different scenarios. Also, different frame rates should all work identical ***EXCEPT*** if the system take a framerate hit, the Timer() seems to go out of wack. Since the functions use the Timer() for the v=at^2 formula, this can cause a sudden increase in velocity.<br /> <br /> Feel free to use these, but please give me credit. Also the prgram uses Memblocks and I'm a newb using them, so definately you are agreeing to use at your own risk (I had no problems though). Also, I would like feedback on this stuff - please and thanks in advance.

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

`Written by Patrick Lewis

`***Demonstration***

Sync On

Sync Rate 40

AutoCam Off

Position Camera 0,0,50,-20

Position Light 0,0,50,10

Set Normalization Off

`Create the Ground

Make Object Plain 100,1000,1000

Pitch Object Down 100,90

Color Object 100,RGB(255,255,0)

Ghost Object On 100

`Create a few random balls.

NumBalls=rnd(20)+20

For i = 1 to NumBalls

Size=rnd(10)+10

Make Object Sphere i,rnd(5)+5

x=rnd(200)-100:y=rnd(100)+50:z=rnd(100)+50

Position Object i, x,y,z

Color Object i,rgb(rnd(255),rnd(255),rnd(255))

Next i

Sync

Sleep 1000

`Woohoo!!! Now Let 'em go.

For i = 1 to NumBalls

Gravity(i)

Bounce(i)

Next i

If RightKey() Then Turn Camera Right 1

If LeftKey() Then Turn Camera Left 1

Sync

Loop

`***End of Demo***

`Bounce & Gravity Functions

Function Gravity(ObjectID)

GForce=-32000:` Working in *1000 Space. It get's divided out later.

Ground#=0

If Object Exist(ObjectID)=0 Then ExitFunction

ObjectID#=ObjectID

V1=Int(ObjectID#/256)

V2=ObjectID#-(V1*256)

ID$=Chr$(V1)+Chr$(V2)

LastYVel=GetStaticVar("GV"+ID$)

LastTime=GetStaticVar("GT"+ID$)

If LastTime<0

StaticVar("GV"+ID$,-1)

StaticVar("GT"+ID$,Timer())

ExitFunction

Endif

NewTime=Timer()

DTime=NewTime-LastTime

NewYVel=LastYVel+(GForce*DTime^2)

NewYVel#=NewYVel

NewYVel#=NewYVel#/(1000^3)

HalfSize#=Object Size Y(ObjectID)/2

Ground#=Ground#+.5

If Object Position Y(ObjectID)-HalfSize#<Ground# And Abs(NewYVel)<5:`Stop sucking

NewYVel=0

NewYVel#=0

Endif

StaticVar("GV"+ID$,NewYVel)

StaticVar("GT"+ID$,NewTime)

Position Object ObjectID,Object Position X(ObjectID),Object Position Y(ObjectID)+NewYVel#,Object Position Z(ObjectID)

EndFunction

Function Bounce(ObjectID)

Bounce#=.95:` Your bounce factor. Use less than 0.99. Use 0 for no bounce.

RestVal=5:` A value to set for the balls to eventually stop bouncing.

Ground#=0:` The Ground lelvel (or you could pass the ground level for variable terrain).

If Object Exist(ObjectID)=0 Then ExitFunction

HalfSize#=Object Size Y(ObjectID)/2:` assumes object center is in it's middle

Y#=Object Position Y(ObjectID)-HalfSize#

If Y#>Ground# then ExitFunction

ObjectID#=ObjectID

V1=Int(ObjectID#/256)

V2=ObjectID#-(V1*256)

ID$=Chr$(V1)+Chr$(V2)

LastYVel#=GetStaticVar("GV"+ID$)

NewYVel#=Abs(LastYVel#)*Bounce#

If NewYVel#<RestVal Then NewYVel#=0:` Eventually come to rest

NewYVel=NewYVel#

StaticVar("GV"+ID$,NewYVel)

StaticVar("GT"+ID$,Timer())

NewYVel#=NewYVel#/(1000^3)

Position Object ObjectID,Object Position X(ObjectID),Object Position Y(ObjectID)+NewYVel#,Object Position Z(ObjectID)

EndFunction

`Written by: Patrick Lewis

`Worked out "variable" functions.

Function StaticVar(VarID$,VarValue)

`Memblocks 242 and 243 should be reserved for the static functions

`Each Static Variable takes up 16 Bytes: 8 for VarID$ and 8 for Value

`The VarID must be 4 characters in length.

If VarID$="" or Len(VarID$)>4 Then ExitFunction

VarID$=VarID$ + Space$(4-Len(VarID$))

`Convert the VarID to a DWord

VarID_DWord = Asc(Left$(VarID$,1))+(256*Asc(Left$(Mid$(VarID$,2),1)))+(65536*Asc(Left$(Mid$(VarID$,3),1)))+(16777216*Asc(Right$(VarID$,1)))

`Determine if Memblock 243 already exists and if it was created by this function

`If the Memblock does not exist, create it.

If Memblock Exist(243)

If Memblock Byte(243,0)<>243 Then Delete Memblock 243

Endif

If Memblock Exist(243)=0

Make Memblock 243,9

Write Memblock Byte 243,0,243

Write Memblock DWord 243,1,VarID_DWord

Write Memblock DWord 243,5,VarValue

ExitFunction

Endif

`At this point, we have a valid memblock created by this function.

`Next, determine if the Variable had been previously created and set pointer

MBSize =Get Memblock Size(243)

Flag=0

For i = 1 to MBSize-8 Step 8

If VarID_DWord = Memblock DWord(243,i)

Flag=1

Endif

If Flag=1 Then Exit

Next i

pointer = i

`The easy part, if the Variable already exists, simply replace the old data.

If Flag = 1

Write Memblock DWord 243,pointer+4,VarValue

ExitFunction

Endif

`The hard part. We have to make the memblock bigger.

If Memblock Exist(242) then Delete Memblock 242

Make Memblock 242,MBSize+8

Copy Memblock 243,242,0,0,MBSize

Delete Memblock 243

Make Memblock 243, MBSize+8

Copy Memblock 242,243,0,0,MBSize+8

Delete Memblock 242

`Now we can write the new data

Write Memblock DWord 243,pointer,VarID_DWord

Write Memblock DWord 243,pointer+4,VarValue

EndFunction

Function GetStaticVar(VarID$)

RetVal=-1:` Default error flag for the return value since there is no negative number functionality.

If VarID$="" or Len(VarID$)>4

ExitFunction RetVal:`Invalid VarID$ name

Else

VarID$=VarID$ + Space$(4-Len(VarID$))

EndIf

VarID_DWord = Asc(Left$(VarID$,1))+(256*Asc(Left$(Mid$(VarID$,2),1)))+(65536*Asc(Left$(Mid$(VarID$,3),1)))+(16777216*Asc(Right$(VarID$,1)))

If Memblock Exist(243)=0 Then ExitFunction RetVal:` The variable was not created or the memblock has been erased.

If Memblock Byte(243,0)<>243 Then ExitFunction RetVal:` Memblock is there but was not created by StaticVar()

`Everything checks out okay, look for the variable name

MBSize =Get Memblock Size(243)

Flag=0

For i = 1 to MBSize-8 Step 8

If VarID_DWord = Memblock DWord(243,i)

Flag=1

Endif

If Flag=1 Then Exit

Next i

pointer = i+4

If Flag = 1 Then RetVal=Memblock DWord(243,pointer)

EndFunction RetVal

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Author Name:	RiiDii
CodeBase Entries:	8

CodeBase - Gravity and Bounce

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