/** This renders a 3-D model to render a (center-only) doughnut/biscuit cutter
    to Wavefront .obj file format for 3-D printing.

    See: http://paulbourke.net/dataformats/obj/
*/

// These can be altered and the model will be automatically recalculated.
sides = 100
outerDiam = 1.2 cm
stopDiam = outerDiam + .4 cm
innerDiam = outerDiam - 1 mm
cylHeight = 1.75 in
cutterHeight = cylHeight + 3 mm
stopHeight = 4 mm

w = new Writer["DonutCutter" + format[outerDiam, cm, 2] + ".obj"]
w.println["# Doughnut cutter by Frink\n"]
w.println["o DoughnutCutter\n"]

cylOutBottom = new array[sides]
cylOutTop    = new array[sides]
cutterTop    = new array[sides]
cylInBottom = new array[sides]
stopBottomOut = new array[sides]
stopTopOut  = new array[sides]

z0 = 0 mm
z1 = -stopHeight

angleStep = circle/sides

// The length unit
u = mm

for i = 0 to sides-1
{
   angle = i angleStep

   xcyl = outerDiam/2 cos[angle]
   ycyl = outerDiam/2 sin[angle]
   zt = cylHeight

   xcutter = innerDiam/2 cos[angle]
   ycutter = innerDiam/2 sin[angle]

   //
   cylOutBottom.push[[xcyl, ycyl, z0, i+1]]
   cylOutTop.push[[xcyl, ycyl, cylHeight, sides+i+1]]
   cutterTop.push[[xcutter, ycutter, cutterHeight, 2 sides+i+1]]
   cylInBottom.push[[xcutter, ycutter, z1, 3 sides+i+1]]

   xstop = stopDiam/2 cos[angle]
   ystop = stopDiam/2 sin[angle]
   stopBottomOut.push[[xstop, ystop, z1, 4 sides+i+1]]
   stopTopOut.push[[xstop, ystop, z0, 5 sides+i+1]]
}

w.println["# Vertex list \n"]

w.println["\n# Cyl out bottom"]
dumpVertices[cylOutBottom, w, u]

w.println["\n# Cyl out top"]
dumpVertices[cylOutTop, w, u]

w.println["\n# Cutter top"]
dumpVertices[cutterTop, w, u]

w.println["\n# Cylinder inner"]
dumpVertices[cylInBottom, w, u]

w.println["\n# Stop top bottom"]
dumpVertices[stopBottomOut, w, u]

w.println["\n# Stop outer top"]
dumpVertices[stopTopOut, w, u]

w.println["# Face list\n"]
//w.println["usemtl Default"]

// Now output the faces.  These should be output by vertex numbers in a
// counterclockwise "out" fashion.

topFace = "f"
bottomFace = new array

for i = 0 to sides-1
{
   // Cyl sides
   w.println["\n# Cyl sides"]
   [xt0, yt0, zt0, ovt0] = cylOutTop@i
   [xb0, yb0, zb0, ovb0] = cylOutBottom@i
   [xt1, yt1, zt1, ovt1] = cylOutTop@((i+1) mod sides)
   [xb1, yb1, zb1, ovb1] = cylOutBottom@((i+1) mod sides)
   w.println["f $ovt0 $ovb0 $ovb1 $ovt1"]

   // Cutter sides
   w.println["\n# Cutter sides"]
   [cutx0, cuty0, cutz0, cutv0] = cutterTop@i
   [cutx1, cuty1, cutz1, cutv1] = cutterTop@((i+1) mod sides)
   w.println["f $cutv0 $ovt0 $ovt1 $cutv1"]

   // Inner surface of cylinder
   w.println["\n# inner sides"]
   [xb0, yb0, zb0, ivb0] = cylInBottom@i
   [xb1, yb1, zb1, ivb1] = cylInBottom@((i+1) mod sides)
   w.println["f $cutv0 $cutv1 $ivb1 $ivb0"]

   // Bottom sides of stop.
   w.println["\n# Bottom sides of stop"]
   [xb0, yb0, zb0, sbo0] = stopBottomOut@i
   [xb1, yb1, zb1, sbo1] = stopBottomOut@((i+1) mod sides)
   w.println["f $ivb0 $ivb1 $sbo1 $sbo0"]

   // Sides of stop.
   w.println["\n# Sides of stop"]
   [xt0, yt0, zt0, sto0] = stopTopOut@i
   [xt1, yt1, zt1, sto1] = stopTopOut@((i+1) mod sides)
   w.println["f $sto0 $sbo0 $sbo1 $sto1"]
   
   // Upper surface of stop.
   w.println["\n# Upper Surface of stop"]
   w.println["f $sto0 $sto1 $ovb1 $ovb0"]
}

w.close[]


/** Dump an array of vertices */
dumpVertices[array, writer, u] :=
{
   for [x,y,z] = array
      writer.println["v " + formatFix[x, u, 5] + " " + formatFix[y, u, 5] + " " + formatFix[z, u, 5]]
}