Example 3 : Complex Machinery

We have several demo programs showing more complex uses of joints. One of them creates a machine with moving parts that has a chain of spheres attached to. Watch as the machine spins, the chain follows, and the towers go flying.

` one of the interesting features of Dark Physics is that of joints, many different
` kinds of joints exist and these can be used in conjunction with rigid bodies
` to form more complex objects, in this tutorial we’re going to create a crane
` with a moving arm and a sphere chain attached to it, a collection of objects
` will also be placed in the scene so we can view the kind of interactions that
` are possible

phy start
sync on
sync rate 60

color backdrop 0

make light 1
set directional light 1, -1, -1, -1

` load 2 images to be used in texturing our objects
load image "metal1.tga", 1
load image "stripe5.png", 100

` make the ground object
make object box 1, 40, 1, 40
position object 1, 0, 0, 0
texture object 1, 1
phy make rigid body static box 1
`ghost object on 1
set alpha mapping on 1, 50

` create a sphere as a background
make object sphere 100, 80
set object cull 100, 0
texture object 100, 100
set alpha mapping on 100, 20

` construct the shaft of the crane
make object box 2, 4, 16, 4
position object 2, 0, 9, 0
texture object 2, 1
phy make rigid body static box 2

` now create the control box to sit on top of the crane
make object box 3, 2, 2, 2
position object 3, 0, 18, 0
texture object 3, 1
phy make rigid body dynamic box 3

` some extra parts are required for the control box as it needs to be attached to
` the shaft of the crane and it also needs a motor joint as it is responsible for
` moving the arm, this can be achieved by using a revolute joint
phy make revolute joint 1, 2, 3, 0, 1, 0, 0, 18, 0

` a long, thin box will be created for the arm of the crane and it will be positioned
` so it is alongside the edge of the control box
make object box 4, 10, 1, 1
position object 4, 6, 18, 0
texture object 4, 1
phy make rigid body dynamic box 4

` with the arm in place a revolute joint can be created to connect it to the control box
` of the crane
phy make revolute joint 3, 2, 4, 0, 1, 0, 0, 18, 0

` the next task is to create the chain of spheres that will be attached to the arm of the
` crane at its end point, this will be done by creating a set of spheres, attaching the
` first sphere to the arm using a ball joint and then attaching the other spheres to each
` other, a simple for loop will help us construct the chain
Y# = 17

for i = 5 to 20
   make object sphere i, 1
   position object i, 10, Y#, 0
   color object i, rgb ( rnd ( 255 ), rnd ( 255 ), rnd ( 255 ) )

   phy make rigid body dynamic sphere i
   phy make sphere joint i, i, i - 1, object position x ( i ), object position y ( i ), object position z ( i )

   color object i, rgb ( rnd ( 255 ), rnd ( 255 ), rnd ( 255 ) )
   set object specular i, rgb ( rnd ( 255 ), rnd ( 255 ), rnd ( 255 ) )
   set object ambient i, 255
   set object specular power i, 255

   Y# = Y# - 1
next i

` now we have the crane in place we can think about creating some objects that the crane
` can interact with - several stacks of cubes will be created and placed around the crane
CreateCubeStack( 21, 35,   0,  17 )
CreateCubeStack( 36, 50,   0, -15 )
CreateCubeStack( 51, 65, -15,  10 )
CreateCubeStack( 66, 80, -10,  -8 )

` position the camera so we can get a good view of the scene
position camera -30, 25, 0
rotate camera 40, 90, 0

load image "logo.png", 10000
sprite 1, 0, 600 - 60, 10000
set sprite 1, 0, 1
backdrop off

y# = -1.0
frame = 0

` now our main loop
do
   inc frame

   if frame = 900
      y# = -0.5
   endif

   if frame = 1800
      y# = -0.25
   endif

   if frame = 2700
      y# = -0.12
   endif

   phy set rigid body angular velocity 4, 0, y#, 0

   ` rotate the backdrop
   rotate object 100, 0, object angle y( 100 ) + 0.1, 0

   ` update the physics and the screen
   phy update
   sync
loop

function CreateCubeStack( start, finish, x, z )
   ` this function will create a stack of cubes with ID numbers between start to finish and
   ` positioned at the locations specified by x and z
   y = 1

   for i = start to finish
      make object cube i, 1
      position object i, x, y, z
      phy make rigid body dynamic box i

      color object i, rgb ( rnd ( 255 ), rnd ( 255 ), rnd ( 255 ) )
      set object specular i, rgb ( rnd ( 255 ), rnd ( 255 ), rnd ( 255 ) )
      set object ambient i, 255
      set object specular power i, 255

      y = y + 1
   next i
endfunction

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