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Car physics

Blitz3D Forums/Blitz3D Beginners Area/Car physics

olo(Posted 2008) [#1]
Hi all, i have made some car models (See here) and was trying to make them move and stuff (car physics). Since i have never done this before i had to find an example, which eventually i found. The problem:
I have almost no clue what any of it means :/
Here's the code:
; Simple car physics by Jeppe Nielsen 2003


Const gravity#=-0.01 ;gravity constant


Graphics3D 640,480,16,2

Const car_col=1
Const world_col=2

Collisions car_col,world_col,2,2


light=CreateLight(1)

RotateEntity light,30,20,0

plane=CreatePlane()

EntityType plane,world_col
EntityColor plane,255,0,0

For n=1 To 100

If Rnd(10)<5

sphere=CreateSphere(16)

Else

sphere=CreateCube()

EndIf

EntityType sphere,world_col
PositionEntity sphere,Rnd(-40,40),Rnd(2),Rnd(-40,40)
EntityColor sphere,Rnd(255),Rnd(255),Rnd(255)

Next

sp=CreateSphere()
ScaleEntity sp,100,100,100
FlipMesh sp

camera=CreateCamera()
CameraClsColor camera,0,0,255


car.car=carnew(0,5,0)

Repeat
TFormPoint 0,3,-5,car\e,0

dx#=(TFormedX()-EntityX(camera))*.1
dy#=(TFormedY()-EntityY(camera))*.1
dz#=(TFormedZ()-EntityZ(camera))*.1

TranslateEntity camera,dx,dy,dz

PointEntity camera,car\e

carcontrol()
carupdate()

RenderWorld()

Flip


Until KeyDown(1)
End


Type car

Field e ;entity

Field x#,y#,z# ; position in 3d-space

Field vx#,vy#,vz# ; velocity

Field ax#,ay#,az# ; acceleration

End Type


Function carnew.car(x#,y#,z#)
	
	c.car=New car
	
	c\x#=x#
	c\y#=y#
	c\z#=z#
	
	c\e=CreateCube()
	cube=CreateCube()
	ScaleEntity cube,0.3,0.3,0.3
	PositionEntity cube,0,0,1
	EntityParent cube,c\e
	
	EntityType c\e,car_col
	EntityRadius c\e,1
	
	PositionEntity c\e,c\x,c\y,c\z
	
	Return c
	
End Function

Function carupdate()
	
	For c.car=Each car
	
		c\vy#=c\vy#+gravity#
		
		c\vx#=c\vx#+c\ax#
		c\vy#=c\vy#+c\ay#
		c\vz#=c\vz#+c\az#
		
		c\x#=EntityX(c\e)
		c\y#=EntityY(c\e)
		c\z#=EntityZ(c\e)
		
		TranslateEntity c\e,c\vx,c\vy,c\vz
	
	Next
	
	UpdateWorld()
	
	For c.car=Each car
		
		;correct velocity if collided
		c\vx=(EntityX(c\e)-c\x)
		c\vy=(EntityY(c\e)-c\y)
		c\vz=(EntityZ(c\e)-c\z)
		
		
		;slow down due to friction
		If EntityCollided(c\e,world_col)
			
			c\vx#=c\vx*0.98
			c\vy#=c\vy*0.98
			c\vz#=c\vz*0.98
		
		EndIf
		
		c\ax#=0
		c\ay#=0
		c\az#=0
		
	Next
	
End Function


Function carcontrol()
	
	For c.car=Each car
		
		If KeyDown(200)
			
			TFormVector 0,0,0.02,c\e,0
			
			c\ax#=TFormedX()
			c\ay#=TFormedY()
			c\az#=TFormedZ()
			
		EndIf
		
		If KeyDown(208)
			
			c\vx=c\vx*0.99
			c\vy=c\vy*0.99
			c\vz=c\vz*0.99
			
		EndIf
		
		If KeyDown(57)
			
			TFormVector 0,0.05,0,c\e,0
			
			c\ax#=c\ax+TFormedX()
			c\ay#=c\ay+TFormedY()
			c\az#=c\az+TFormedZ()
			
									
		EndIf
		
		If KeyDown(203)
			
			TurnEntity c\e,0,2,0
			
		EndIf
		
		If KeyDown(205)
			
			TurnEntity c\e,0,-2,0
			
		EndIf
		
		
	Next
	
	
	
End Function


Can somebody please explain to me what this means. Even if you know parts please help me understand

Thanks


olo(Posted 2008) [#2]
If anyone has more understandable or better car physics then please help me and post it up, i'd much appreciate it.
The stuff above is really what i am looking for but i would like to incorporate these to my own models..not the cube. Unfortunately, since i dont know which parts of the code are which, i am unable to do this.

Please help if you can
Thanks


Moraldi(Posted 2008) [#3]
if anyone has more understandable or better car physics...

If you understand nothing from the code above then I advise
you to start learning Blitz3D commands.
If you have specific question then ask


olo(Posted 2008) [#4]
I understand all hte commands above, its just that i dont understand the authors' coding. For example, i am having trouble finding which part makes the 'car' move up when it collides.. stuff like that. I get the code until about half way. Here is where i get lost:

car.car=carnew(0,5,0)

Repeat
TFormPoint 0,3,-5,car\e,0

dx#=(TFormedX()-EntityX(camera))*.1
dy#=(TFormedY()-EntityY(camera))*.1
dz#=(TFormedZ()-EntityZ(camera))*.1

TranslateEntity camera,dx,dy,dz

PointEntity camera,car\e

carcontrol()
carupdate()

RenderWorld()

Flip


Until KeyDown(1)
End


Type car

Field e ;entity

Field x#,y#,z# ; position in 3d-space

Field vx#,vy#,vz# ; velocity

Field ax#,ay#,az# ; acceleration

End Type


Function carnew.car(x#,y#,z#)
	
	c.car=New car
	
	c\x#=x#
	c\y#=y#
	c\z#=z#
	
	c\e=CreateCube()
	cube=CreateCube()
	ScaleEntity cube,0.3,0.3,0.3
	PositionEntity cube,0,0,1
	EntityParent cube,c\e
	
	EntityType c\e,car_col
	EntityRadius c\e,1
	
	PositionEntity c\e,c\x,c\y,c\z
	
	Return c
	
End Function

Function carupdate()
	
	For c.car=Each car
	
		c\vy#=c\vy#+gravity#
		
		c\vx#=c\vx#+c\ax#
		c\vy#=c\vy#+c\ay#
		c\vz#=c\vz#+c\az#
		
		c\x#=EntityX(c\e)
		c\y#=EntityY(c\e)
		c\z#=EntityZ(c\e)
		
		TranslateEntity c\e,c\vx,c\vy,c\vz
	
	Next
	
	UpdateWorld()
	
	For c.car=Each car
		
		;correct velocity if collided
		c\vx=(EntityX(c\e)-c\x)
		c\vy=(EntityY(c\e)-c\y)
		c\vz=(EntityZ(c\e)-c\z)
		
		
		;slow down due to friction
		If EntityCollided(c\e,world_col)
			
			c\vx#=c\vx*0.98
			c\vy#=c\vy*0.98
			c\vz#=c\vz*0.98
		
		EndIf
		
		c\ax#=0
		c\ay#=0
		c\az#=0
		
	Next
	
End Function


Function carcontrol()
	
	For c.car=Each car
		
		If KeyDown(200)
			
			TFormVector 0,0,0.02,c\e,0
			
			c\ax#=TFormedX()
			c\ay#=TFormedY()
			c\az#=TFormedZ()
			
		EndIf
		
		If KeyDown(208)
			
			c\vx=c\vx*0.99
			c\vy=c\vy*0.99
			c\vz=c\vz*0.99
			
		EndIf
		
		If KeyDown(57)
			
			TFormVector 0,0.05,0,c\e,0
			
			c\ax#=c\ax+TFormedX()
			c\ay#=c\ay+TFormedY()
			c\az#=c\az+TFormedZ()
			
									
		EndIf
		
		If KeyDown(203)
			
			TurnEntity c\e,0,2,0
			
		EndIf
		
		If KeyDown(205)
			
			TurnEntity c\e,0,-2,0
			
		EndIf
		
		
	Next
	
	
	
End Function


if anyone knows what this means, or at least parts of it, then please tell me or add comments (;) to the code as it has none.

Thanks


blackbag(Posted 2008) [#5]
It's using staight blitz collsions nothing special. The lines below set this up.

[code]
Const car_col=1
Const world_col=2

Collisions car_col,world_col,2,2
[\code]

The car is created with type car_col and everything else with world_col. When the "car" collides with somthing it slides over and around it as per the collision parameters above.


olo(Posted 2008) [#6]
ok, i have read and reread that code about 100 times and i still dont understand what i would replace or add/take away from the code to allow my model to have the exact same properties as the cube does in this example.
Lets say my model is a sphere instead of the cube that acts as the car above. What parts of the code would i take away, replace or change so that the player would now drive a sphere around the 'world' instead of that cube.

Please does anyone know
Quite desperate... :0(


Ross C(Posted 2008) [#7]
I agree, you should learn more blitz ;o)

From the above, he uses a create_car function. That gives you a clue :o) And since he's creating a cube, the CreateCube() function further narrows it down:

Function carnew.car(x#,y#,z#)
	
	c.car=New car
	
	c\x#=x#
	c\y#=y#
	c\z#=z#
	
	c\e=CreateCube()
	cube=CreateCube()
	ScaleEntity cube,0.3,0.3,0.3
	PositionEntity cube,0,0,1
	EntityParent cube,c\e
	
	EntityType c\e,car_col
	EntityRadius c\e,1
	
	PositionEntity c\e,c\x,c\y,c\z
	
	Return c
	
End Function


Try changing the two above CreateCube() functions to whatevershape you want and see if that works :o)


olo(Posted 2008) [#8]
ok erm...
here is the problem, the models which i want to use (which are modeled in blitz3d using cubes and spheres *See Here*) are made up of much more code than just createsphere/cube as i used many spheres/cubes. Then i parented everything to one of the parts of the model (a cube named 'body').

So...where do i paste all the code and what will i need to change? :(

Thanks


Ross C(Posted 2008) [#9]
In here:

	c\e= loadmesh("yourmodel.b3d")
        cube= loadmesh("yourmodel.b3d")


What i'm unsure of though, is the two cubes. I assume one of them is for collisions, so play about with it and i'm sure you'll get it. Or, send me the code + model you want to my email and i'll have a play about with it.


olo(Posted 2008) [#10]
ok Ross, thanks so much. I have sent the code of one of the models to your e-mail together with the code of the example.
Please tell me if you have figuered something out, i'll be trying too in the meantime.

Thanks again.


Moraldi(Posted 2008) [#11]
Then i parented everything to one of the parts of the model (a cube named 'body').

Change the following function:
Function carnew.car(x#,y#,z#)
	
	c.car=New car
	
	c\x#=x#
	c\y#=y#
	c\z#=z#
	
	c\e=CreateCube()
	cube=CreateCube()
	ScaleEntity cube,0.3,0.3,0.3
	PositionEntity cube,0,0,1
	EntityParent cube,c\e
	
	EntityType c\e,car_col
	EntityRadius c\e,1
	
	PositionEntity c\e,c\x,c\y,c\z
	
	Return c
	
End Function


to this:
Function carnew.car(x#,y#,z#, carmodel%)
	
	c.car=New car
	
	c\x#=x#
	c\y#=y#
	c\z#=z#
	
	c\e=CreateCube()
	PositionEntity carmodel,0,0,1
	EntityParent carmodel,c\e
	
	EntityType c\e,car_col
	EntityRadius c\e,1
	
	PositionEntity c\e,c\x,c\y,c\z
	
	Return c
	
End Function


and change the following line:
car.car=carnew(0,5,0)


to
car.car=carnew(0,5,0, body)



olo(Posted 2008) [#12]
Thank you so much, it finally works, i just ave one problem...
when i run the program, i see my model with a bigish cube sticking out of the top..
When i try scaling it the collisions dont really work anymore, any ideas on how to fix this?

Thanks so much anyway


Moraldi(Posted 2008) [#13]
Try to change the value of 1 in line of function 'carnew'
EntityRadius c\e,1

to a larger or smaller value
But I insist to read the Blitz3D manual... :)


olo(Posted 2008) [#14]
Oh, its ok , i figuered it out.
I set EntityAlpha to 0 for c\e:
EntityAlpha c\e, 0


Thanks for all the help, i will probably be back asking for more later anyway.

Bye for now


Ross C(Posted 2008) [#15]
Dam, just got back too :oP Glad you got it fixed though!