ODE: Basic steps

[José Roca]

 
The following example shows you the very basics of ODE: creating a world including a rigid body and doing a simulation loop. The example program does without any fancy graphics output, but just displays the bare numbers.

It is a translation of PyODE Tutorial 1, by Matthias Baas.
See: http://pyode.sourceforge.net/tutorials/tutorial1.html

Code Select Expand


' SED_PBWIN - Use the PBWIN compiler
#COMPILE EXE
#DIM ALL
#INCLUDE "ODE.INC"

FUNCTION PBMAIN () AS LONG

   LOCAL pWorld AS DWORD
   LOCAL pBody AS DWORD
   LOCAL tMass AS dMass
   LOCAL total_time AS DOUBLE
   LOCAL dt AS DOUBLE
   LOCAL ps AS SINGLE PTR
   LOCAL x, y, z AS SINGLE
   LOCAL u, v, w AS SINGLE
   LOCAL strOut AS STRING
   
   ' Create new world
   pWorld = dWorldCreate
   ' Create general body
   pBody = dBodyCreate(pWorld)
   ' Planet Earth
   dWorldSetGravity(pWorld, 0, -9.81, 0)
   ' Give density and radius
   dMassSetSphere(tMass, 2500.0, 0.05)
   ' Actual mass
   tMass.mass = 1
   ' Assign mass to the body
   dBodySetMass(pBody, tMass)
   ' Position mass at x, y, z
   dBodySetPosition(pBody, 0, 2, 0)
   ' Add force
   dBodyAddForce(pBody, 0, 200, 0)
   ' Do the simulation
   dt = 0.04
   WHILE total_time < 2.0!
      ps = dBodyGetPosition(pBody)
      IF ps THEN
         x = @ps[0]
         y = @ps[1]
         z = @ps[2]
      END IF
      ps = dBodyGetLinearVel(pBody)
      IF ps THEN
         u = @ps[0]
         v = @ps[1]
         w = @ps[2]
      END IF
      strOut = strOut & FORMAT$(total_time, "0.00") & " sec: " & _
               "pos = (" & FORMAT$(x, "0.000") & "," & FORMAT$(y, "0.000") & "," & FORMAT$(z, "0.000") & ")" & _
               "vel = (" & FORMAT$(u, "0.000") & "," & FORMAT$(v, "0.000") & "," & FORMAT$(w, "0.000") & ")" & $CRLF
      ' Increase step in simulation
      dWorldStep(pWorld, dt)
      total_time = total_time + dt
   WEND

   ' Cleanup
   IF pBody THEN dBodyDestroy(pBody)
   IF pWorld THEN dWorldDestroy(pWorld)

   MSGBOX strOut

END FUNCTION


[Kent Sarikaya]

Thanks Jose, I should mention that Petr is writing some great ODE examples in thinBasic also. Just wanted others getting into ODE to know they can look at his code to get an idea too at the thinBasic forums.

http://community.thinbasic.com/index.php?board=103.0