"Patrick Elliott" <sha### [at] hotmailcom> wrote in message
news:MPG.19836835a2284e4b98983c@news.povray.org...
> In article <3f192104$1@news.povray.org>, tim### [at] gmxde says...
> > It does sound interesting, but also a little above
> > my head at the moment... Nontheless, thanks
> > for link, perhaps I can make something of it when
> > having more time to spend on it...
> >
>
> Simplest definition is that Inverse Kinematics uses some sort of nesting
> of objects. In SDL this is easy:
>
> union {
>   Object1
>   Object {
>     Object2
>     rotate <x2,y2,z2>
>   }
>   rotate <x1,y1,z1>
> }
>
An array-based approach works too.

#declare ataObjs = array[8] { ataBase, ataSectB, ataSectM, ataSectM,
ataSectM, ataSectH, ataHandL, ataHandR }
#declare ataLens = array[8] { atabHgtB, atasH, atasH, atasH, atasH, atasH,
0, 0 }
#declare atArmAng = array[1][3]
#declare atArmAng[0][0] = array[7] { <-40, 20,-35>, x*26, x*30 , x*28, x*33,
x* 5,-x*10 }
#declare atArmAng[0][1] = array[7] { < 10, 70,  5>, x* 6, x* 4 , x* 8, x*13,
x*10,-x*20 }
#declare atArmAng[0][2] = array[7] { <- 3,-90,-15>, x*10, x* 8 , x*14, x*11,
x*15,-x*30 }
#declare ataMoves = array[7]

#macro ManipArm(Objects, Lengths, Joints, Moves)
 #local aSiz = dimension_size(Joints,1);
 #debug concat(str(aSiz,0,0), " objects.\n")
 #local ps = 0;
 #while (ps<aSiz)
  #local rt = ps;
  #declare Moves[ps] = transform {
   #while (rt>=0)
    rotate Joints[rt]
    translate y*Lengths[rt]
    #local rt = rt - 1;
   #end
  }
  #local ps = ps + 1;
 #end
 union {
  #set ps = 0;
  object { Objects[ps] }
  #while (ps<aSiz)
   #local ps = ps + 1;
   object { Objects[ps] transform { Moves[ps-1] } }
  #end
 }
#end

#macro atArm(obn, arn) object { ManipArm(ataObjs, ataLens,
atArmAng[obn][arn], ataMoves) } #end

The idea is to set up the transforms for each object first so that nesting
becomes unnecessary:

If you want the object definitions check out my "Manipulator arm" thread.

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