Newton Physics Code Snippet - GameCreators Forum

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Physics coder

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Joined: 25th May 2004

Location: United States

Posted: 7th Aug 2004 13:43

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Made this for fun, and hopefully a basic starting point for whoever wants to try Newton Physics but wants to set the position/rotation/velocity/whatever like normal objects.

Some functions that might be useful that are in the code snippet:

make_box(object number,x size,y size z size,mass,surface type, move flag)
makes a DBP object and a body with one command. IF the move flah is 1, the box can move and will if it collides with other objects and will be affected by gravity, else the object will remain still and only move with the next function.

set_object(object number,x position,y position,z position,x angle,y angle,z angle)
this function sets the object's and body's position and rotation.

set_velocity(object number, x velocity, y velocity, z velocity)
this function sets the linear velocity of the object.

set_omega(object number, x velocity, y velocity, z velocity)
this function sets the rotational velocity of the object.

add_velocity(object number, x velocity, y velocity, z velocity)
this functions increases the velocity of the object.

add_omega(object number, x velocity, y velocity, z velocity)
this functions increases the rotational velocity of the object.

set_relative_velocity(object number, x velocity, y velocity, z velocity)
this functions sets the velocity relative to the object, so a positive z velocity will make the object go forward no matter what direction it's facing.

set_relative_omega(object number, x velocity, y velocity, z velocity)
this functions sets the rotational velocity relative to the object, so a non-zero z velocity will make the object roll no matter what direction it's facing.

add_relative_velocity(object number, x velocity, y velocity, z velocity)
this functions increases the velocity relative to the object, so a positive z velocity will accelerate the object forward no matter what direction it's facing.

add_relative_omega(object number, x velocity, y velocity, z velocity)
this functions increases the rotational velocity relative to the object, so a positive y velocity will accelerate the object to the right no matter what direction it's facing.

Using these functions you don't have to worry about the bodies or what object is the visual representation of what body.

`screen stuff
sync on
sync rate 0
cls
hide mouse
`turn of automatic camera
autocam off

`make an array of all the objects(this must be as large as the amount of objects in the demo)
type object_type
   body
   move
endtype
dim obj(100) as object_type

`this starts newton
NDB_NewtonCreate

`create one material
global BOX_ID=NDB_NewtonMaterialCreateGroupID()

`make a floor
n=0
`1000,10,1000 is the x,y,z size of the floor, with the box id.
`the last number, 0, means the floor is stationary, or else it would fall
inc n:make_box(n,1000,10,1000,1,BOX_ID,0)
`this positions the floor at 500,-5,500 and rotates it at 0,0,0
`if you want change last three to 0,45,0 to see the floor rotated 45 degrees on the y axis
set_object(n,500,-5,500,0,0,0)

`this makes and positions 4 walls, one on each side:
`make wall 1
inc n:make_box(n,10,100,1000,1,BOX_ID,0)
`position wall 1
set_object(n,-5,50,500,0,0,0)

`make wall 2
inc n:make_box(n,10,100,1000,1,BOX_ID,0)
`position wall 2
set_object(n,1005,50,500,0,0,0)

`make wall 3
inc n:make_box(n,1000,100,10,1,BOX_ID,0)
`position wall 3
set_object(n,500,50,-5,0,0,0)

`make wall 4
inc n:make_box(n,1000,100,10,1,BOX_ID,0)
`position wall 4
set_object(n,500,50,1005,0,0,0)

`this is the box the player controls
inc n:make_box(n,10,5,15,1,BOX_ID,1)
`color it green
color object n,rgb(0,255,0)
`position it
set_object(n,400,6,500,0,0,0)

`this makes 94(100-1 floor-4 walls-1 player) boxes
repeat
   `make the box
   inc n:make_box(n,30,10,30,1,BOX_ID,1)
   `position the box on the floor, with a y angle of rnd(359)
   set_object(n,rnd(1000-200)+100,5,rnd(1000-200)+100,0,rnd(359),0)
   `color it light blue
   color object n,rgb(100,100,255)
until n=100

`position the camera
position camera 500,20,500

`make the time variable
global time#=NDB_GetElapsedTimeInSec()
time#=NDB_GetElapsedTimeInSec()
control$="CAR"
do
   `this controls it like a rocket, press up to travel up in the direction of the rocket
   `if the rocket is pointing down the rocket will go down when you press up, etc.
   set cursor 0,0
   print "(1) Car controls"
   print "(2) Rocket controls"
   if keystate(3)=1 then control$="ROCKET"
   if keystate(2)=1 then control$="CAR"
   if control$="ROCKET"
      add_relative_velocity(6,0,(upkey()-downkey())*60*time#,0)
      `w/a/s/d controls the angle acceleration, left/right arrow keys roll the rocket
      add_relative_omega(6,(keystate(17)-keystate(31))*10*time#,(rightkey()-leftkey())*10*time#,(keystate(30)-keystate(32))*10*time#)
   endif
   if control$="CAR"
      add_relative_velocity(6,0,0,(upkey()-downkey())*60*time#)
      add_relative_omega(6,0,(rightkey()-leftkey())*10*time#,0)
   endif
   `update the newton stuff
   time#=NDB_GetElapsedTimeInSec()
   NDB_NewtonUpdate time#

`mouse look camera
   gosub camera
   sync
loop

camera:
   rotate camera wrapvalue(camera angle x()+mousemovey()),wrapvalue(camera angle y()+mousemovex()),0
   if mouseclick()<>0
      inc move#,0.1
      if mouseclick()=1 then move camera move# else move camera -move#
   else
      move#=0
   endif
return

function make_box(obj_num,xs#,ys#,zs#,mass#,group_id,move)
   `this makes a newton box
   make object box obj_num, xs#,ys#,zs#
   col = NDB_NewtonCreateBox(xs#,ys#,zs#)
   body=NDB_NewtonCreateBody(col)
   NDB_BodySetDBProData body, obj_num
   NDB_SetVector 0,0,0
   NDB_SetVectorToRadians
   NDB_NewtonSetEulerAngle
   NDB_SetVector 0,0,0, 1.0
   NDB_SetMatrixPosRow
   NDB_NewtonBodySetMatrix body
`   NDB_NewtonBodySetDestructorCallback body
   NDB_NewtonBodySetMaterialGroupID body, group_id
   NDB_NewtonBodySetTransformCallback body
   if move=1
      NDB_NewtonBodySetForceAndTorqueCallback body
      NDB_CalculateMIBoxSolid mass#,xs#,ys#,zs#
      NDB_NewtonBodySetMassMatrix Body, mass#
      NDB_NewtonBodySetAutoFreeze body, 0
   else
      NDB_NewtonBodySetAutoFreeze body, 1
   endif
   obj(obj_num).move=move
   obj(obj_num).body=body
endfunction body

function set_object(objnum,xp#,yp#,zp#,xr#,yr#,zr#)
   NDB_SetVector xr#,yr#,zr#
   NDB_SetVectorToRadians
   NDB_NewtonSetEulerAngle
   NDB_SetVector xp#, yp#, zp#, 1.0
   NDB_SetMatrixPosRow
   NDB_NewtonBodySetMatrix obj(objnum).body
   position object objnum,xp#,yp#,zp#
   rotate object objnum,wrapvalue(xr#),wrapvalue(yr#),wrapvalue(zr#)
endfunction

function set_velocity(objnum,x#,y#,z#)
   REM set the speed of a body
   NDB_SetVector x#,y#,z#
   NDB_NewtonBodySetVelocity obj(objnum).body
endfunction

function set_omega(objnum,x#,y#,z#)
   REM set the omega(rotational velocity) of a body
   NDB_SetVector x#,y#,z#
   NDB_NewtonBodySetOmega obj(objnum).body
endfunction

function add_velocity(objnum,x#,y#,z#)
   REM adds velocity to the body
   `get speed of body
   NDB_NewtonBodyGetVelocity obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+x#, NDB_GetVector_Y()+y#, NDB_GetVector_Z()+z#
   `set the speed of a body
   NDB_NewtonBodySetVelocity obj(objnum).body
endfunction

function add_omega(objnum,x#,y#,z#)
   REM set the speed of a body
   NDB_NewtonBodyGetOmega obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+x#, NDB_GetVector_Y()+y#, NDB_GetVector_Z()+z#
   NDB_NewtonBodySetOmega obj(objnum).body
endfunction

function add_relative_velocity(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

NDB_NewtonBodyGetVelocity obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+ax#, NDB_GetVector_Y()+ay#, NDB_GetVector_Z()+az#
   `set the speed of a body
   NDB_NewtonBodySetVelocity obj(objnum).body

endfunction

function set_relative_velocity(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

NDB_SetVector ax#, ay#, az#
   `set the speed of a body
   NDB_NewtonBodySetVelocity obj(objnum).body

endfunction

function add_relative_omega(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

NDB_NewtonBodyGetOmega obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+ax#, NDB_GetVector_Y()+ay#, NDB_GetVector_Z()+az#
   `set the speed of a body
   NDB_NewtonBodySetOmega obj(objnum).body

endfunction

function set_relative_omega(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

NDB_SetVector ax#, ay#, az#
   `set the speed of a body
   NDB_NewtonBodySetOmega obj(objnum).body

endfunction

+ Code Snippet

`screen stuff
sync on
sync rate 0
cls
hide mouse
`turn of automatic camera
autocam off

`make an array of all the objects(this must be as large as the amount of objects in the demo)
type object_type
   body
   move
endtype
dim obj(100) as object_type

`this starts newton
NDB_NewtonCreate

`create one material
global BOX_ID=NDB_NewtonMaterialCreateGroupID()

`make a floor
n=0
`1000,10,1000 is the x,y,z size of the floor, with the box id.
`the last number, 0, means the floor is stationary, or else it would fall
inc n:make_box(n,1000,10,1000,1,BOX_ID,0)
`this positions the floor at 500,-5,500 and rotates it at 0,0,0
`if you want change last three to 0,45,0 to see the floor rotated 45 degrees on the y axis
set_object(n,500,-5,500,0,0,0)

`this makes and positions 4 walls, one on each side:
`make wall 1
inc n:make_box(n,10,100,1000,1,BOX_ID,0)
`position wall 1
set_object(n,-5,50,500,0,0,0)

`make wall 2
inc n:make_box(n,10,100,1000,1,BOX_ID,0)
`position wall 2
set_object(n,1005,50,500,0,0,0)

`make wall 3
inc n:make_box(n,1000,100,10,1,BOX_ID,0)
`position wall 3
set_object(n,500,50,-5,0,0,0)

`make wall 4
inc n:make_box(n,1000,100,10,1,BOX_ID,0)
`position wall 4
set_object(n,500,50,1005,0,0,0)


`this is the box the player controls
inc n:make_box(n,10,5,15,1,BOX_ID,1)
`color it green
color object n,rgb(0,255,0)
`position it
set_object(n,400,6,500,0,0,0)

`this makes 94(100-1 floor-4 walls-1 player) boxes
repeat
   `make the box
   inc n:make_box(n,30,10,30,1,BOX_ID,1)
   `position the box on the floor, with a y angle of rnd(359)
   set_object(n,rnd(1000-200)+100,5,rnd(1000-200)+100,0,rnd(359),0)
   `color it light blue
   color object n,rgb(100,100,255)
until n=100

`position the camera
position camera 500,20,500

`make the time variable
global time#=NDB_GetElapsedTimeInSec()
time#=NDB_GetElapsedTimeInSec()
control$="CAR"
do
   `this controls it like a rocket, press up to travel up in the direction of the rocket
   `if the rocket is pointing down the rocket will go down when you press up, etc.
   set cursor 0,0
   print "(1) Car controls"
   print "(2) Rocket controls"
   if keystate(3)=1 then control$="ROCKET"
   if keystate(2)=1 then control$="CAR"
   if control$="ROCKET"
      add_relative_velocity(6,0,(upkey()-downkey())*60*time#,0)
      `w/a/s/d controls the angle acceleration, left/right arrow keys roll the rocket
      add_relative_omega(6,(keystate(17)-keystate(31))*10*time#,(rightkey()-leftkey())*10*time#,(keystate(30)-keystate(32))*10*time#)
   endif
   if control$="CAR"
      add_relative_velocity(6,0,0,(upkey()-downkey())*60*time#)
      add_relative_omega(6,0,(rightkey()-leftkey())*10*time#,0)
   endif
   `update the newton stuff
   time#=NDB_GetElapsedTimeInSec()
   NDB_NewtonUpdate time#

   `mouse look camera
   gosub camera
   sync
loop

camera:
   rotate camera wrapvalue(camera angle x()+mousemovey()),wrapvalue(camera angle y()+mousemovex()),0
   if mouseclick()<>0
      inc move#,0.1
      if mouseclick()=1 then move camera move# else move camera -move#
   else
      move#=0
   endif
return

function make_box(obj_num,xs#,ys#,zs#,mass#,group_id,move)
   `this makes a newton box
   make object box obj_num, xs#,ys#,zs#
   col = NDB_NewtonCreateBox(xs#,ys#,zs#)
   body=NDB_NewtonCreateBody(col)
   NDB_BodySetDBProData body, obj_num
   NDB_SetVector 0,0,0
   NDB_SetVectorToRadians
   NDB_NewtonSetEulerAngle
   NDB_SetVector 0,0,0, 1.0
   NDB_SetMatrixPosRow
   NDB_NewtonBodySetMatrix body
`   NDB_NewtonBodySetDestructorCallback body
   NDB_NewtonBodySetMaterialGroupID body, group_id
   NDB_NewtonBodySetTransformCallback body
   if move=1
      NDB_NewtonBodySetForceAndTorqueCallback body
      NDB_CalculateMIBoxSolid mass#,xs#,ys#,zs#
      NDB_NewtonBodySetMassMatrix Body, mass#
      NDB_NewtonBodySetAutoFreeze body, 0
   else
      NDB_NewtonBodySetAutoFreeze body, 1
   endif
   obj(obj_num).move=move
   obj(obj_num).body=body
endfunction body

function set_object(objnum,xp#,yp#,zp#,xr#,yr#,zr#)
   NDB_SetVector xr#,yr#,zr#
   NDB_SetVectorToRadians
   NDB_NewtonSetEulerAngle
   NDB_SetVector xp#, yp#, zp#, 1.0
   NDB_SetMatrixPosRow
   NDB_NewtonBodySetMatrix obj(objnum).body
   position object objnum,xp#,yp#,zp#
   rotate object objnum,wrapvalue(xr#),wrapvalue(yr#),wrapvalue(zr#)
endfunction

function set_velocity(objnum,x#,y#,z#)
   REM set the speed of a body
   NDB_SetVector x#,y#,z#
   NDB_NewtonBodySetVelocity obj(objnum).body
endfunction

function set_omega(objnum,x#,y#,z#)
   REM set the omega(rotational velocity) of a body
   NDB_SetVector x#,y#,z#
   NDB_NewtonBodySetOmega obj(objnum).body
endfunction

function add_velocity(objnum,x#,y#,z#)
   REM adds velocity to the body
   `get speed of body
   NDB_NewtonBodyGetVelocity obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+x#, NDB_GetVector_Y()+y#, NDB_GetVector_Z()+z#
   `set the speed of a body
   NDB_NewtonBodySetVelocity obj(objnum).body
endfunction

function add_omega(objnum,x#,y#,z#)
   REM set the speed of a body
   NDB_NewtonBodyGetOmega obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+x#, NDB_GetVector_Y()+y#, NDB_GetVector_Z()+z#
   NDB_NewtonBodySetOmega obj(objnum).body
endfunction

function add_relative_velocity(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

   y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

   z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

   ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

   NDB_NewtonBodyGetVelocity obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+ax#, NDB_GetVector_Y()+ay#, NDB_GetVector_Z()+az#
   `set the speed of a body
   NDB_NewtonBodySetVelocity obj(objnum).body

endfunction

function set_relative_velocity(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

   y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

   z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

   ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

   NDB_SetVector ax#, ay#, az#
   `set the speed of a body
   NDB_NewtonBodySetVelocity obj(objnum).body

endfunction

function add_relative_omega(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

   y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

   z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

   ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

   NDB_NewtonBodyGetOmega obj(objnum).body
   `add input velocities
   NDB_SetVector NDB_GetVector_X()+ax#, NDB_GetVector_Y()+ay#, NDB_GetVector_Z()+az#
   `set the speed of a body
   NDB_NewtonBodySetOmega obj(objnum).body

endfunction

function set_relative_omega(objnum,x#,y#,z#)
   NDB_NewtonBodyGetMatrix obj(objnum).body
   NDB_GetMatrix
   x_x# = NDB_GetVector_X(1)
   x_y# = NDB_GetVector_Y(1)
   x_z# = NDB_GetVector_Z(1)

   y_x# = NDB_GetVector_X(2)
   y_y# = NDB_GetVector_Y(2)
   y_z# = NDB_GetVector_Z(2)

   z_x# = NDB_GetVector_X(3)
   z_y# = NDB_GetVector_Y(3)
   z_z# = NDB_GetVector_Z(3)

   ax#=x#*x_x#+y#*y_x#+z#*z_x#
   ay#=x#*x_y#+y#*y_y#+z#*z_y#
   az#=x#*x_z#+y#*y_z#+z#*z_z#

   NDB_SetVector ax#, ay#, az#
   `set the speed of a body
   NDB_NewtonBodySetOmega obj(objnum).body

endfunction

Controls arrow keys for turn left/right and forward/backward during car controls, during rocket controls arrow keys are same but up/down control the up/down acceleration, and WASD control the x and z axis rotational acceleration.

-----------------------------------
To delete the bug, delete the code.
Specs: Sony VAIO Laptop, Windows XP, P4 2.8Ghz, 512MB RAM, ATI Radeon 64MB video memory, DBP Upgrade 5.3.

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walaber

21

Years of Service

User Offline

Joined: 22nd Oct 2003

Location: Los Angeles, CA

Posted: 7th Aug 2004 15:16

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interesting command set. very nice use of the matrix system to make relative (local space) movement.

one note about the methods used in this system: directly setting the velocity / omega effectively gives the rigid body an infinite amount of energy, so collisions between it and other bodies will not be realistic- the other body will be sent flying, and the moving body will hardly be effected, regardless of mass settings.

these functions are actually intended for setting initial velocities and omegas (and testing purposes), not for realtime control.

for physics-sound control, look into setting forces and torques on the bodies with the NDB_BodySetGravity / NDB_BodySetTorque commands.

if you want a specific velocity, you can use algebra to determine the force necessary to result in the desired velocity. it's a little more work and math, but it'll make for a more realistic simulation.

Go Go Gadget DBPRO!

Athlon XP 2400+ || DDR-SDRAM 1GB || Nvidia GeForce 4 Ti4200 AGP 8x 128MB

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Physics coder

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Joined: 25th May 2004

Location: United States

Posted: 8th Aug 2004 05:23

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Hey walaber, thanks for trying the snippet.

Quote: "one note about the methods used in this system: directly setting the velocity / omega effectively gives the rigid body an infinite amount of energy,"

I don't exactly set the velocity, I increase it, so when you colide with a box with the same mass, both of the body will be affected, but the car will have an acceleration to go forward. It looks perfectly realistic to me, when you set the mass of the boxes higher, they are harder to move, until eventually, with enough mass, they are impossible to move. In the example I increase the velocity of the "car" (not set the velocity), and that is what a gravity would do.

Quote: "so collisions between it and other bodies will not be realistic- the other body will be sent flying, and the moving body will hardly be effected, regardless of mass settings."

If it's not realistic, could you make a snippet that shows the difference between increasing the velocity and setting a gravity?

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Code Snippets / Newton Physics Code Snippet