From bfdc8d5fb975fee957566560bf1c9e671a8a571e Mon Sep 17 00:00:00 2001
From: Christian daheim <auriocus@gmx.de>
Date: Wed, 18 Jun 2014 23:54:31 +0200
Subject: [PATCH] Demonstration of rigid 3D coordinate transform

---
 demo/3dcanvas.tcl | 113 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 demo/3dcanvas.tcl

diff --git a/demo/3dcanvas.tcl b/demo/3dcanvas.tcl
new file mode 100644
index 0000000..bcde40c
--- /dev/null
+++ b/demo/3dcanvas.tcl
@@ -0,0 +1,113 @@
+package require Tk
+package require vectcl
+namespace import vectcl::*
+
+# this demonstration shows how to use VecTcl
+# to perform an orthogonal 3D transform on a set of points
+# and display it on a canvas.
+
+
+
+# define the coordinates for a cube with size 2 in the
+# center of the coordsys
+# each two coordinates are connected with a line
+# first top, then bottom, finally the 4 columns between 
+# ceiling and bottom
+set	cube {
+		{1 -1 1}
+		{1 1 1}
+		{1 1 1}
+		{-1 1 1}
+		{-1 1 1}
+		{-1 -1 1}
+		{-1 -1 1}
+		{1 -1 1}
+		
+		{1 -1 -1}
+		{1 1 -1}
+		{1 1 -1}
+		{-1 1 -1}
+		{-1 1 -1}
+		{-1 -1 -1}
+		{-1 -1 -1}
+		{1 -1 -1}
+
+		{1 -1 -1}
+		{1 -1  1}
+		{-1 -1 -1}
+		{-1 -1 1}
+		{-1 1 -1}
+		{-1 1  1}
+		{1 1  -1}
+		{1 1   1}
+	}
+
+vproc eulerx {phi} {
+	list( \
+		list(1.0, 0.0, 0.0), \
+		list(0.0, cos(phi), sin(phi)), \
+		list(0.0, -sin(phi), cos(phi)))
+}
+
+vproc eulery {phi} {
+	list( \
+		list(cos(phi), 0.0, sin(phi)), \
+		list(0.0, 1.0, 0.0), \
+		list(-sin(phi), 0.0, cos(phi)))
+}
+
+vproc eulerz {phi} {
+	list( \
+		list(cos(phi), sin(phi), 0.0), \
+		list(-sin(phi), cos(phi), 0.0), \
+		list(0.0, 0.0, 1.0))
+}
+
+vproc euler {phi chi psi} {
+	# this function returns the 
+	# subsequent rotation around the axis x,y,z
+	# with angles phi, chi, psi
+	# it is slow, but only called once for every frame
+	eulerz(psi)*eulery(chi)*eulerx(phi)
+}
+
+# create a canvas 
+canvas .c -width 500 -height 500
+# four sliders
+ttk::scale .s -variable s -from 1.0 -to 250.0 -command updatePlot
+ttk::scale .phi -variable phi -from 0.0 -to 6.28 -command updatePlot
+ttk::scale .chi -variable chi -from 0.0 -to 6.28 -command updatePlot
+ttk::scale .psi -variable psi -from 0.0 -to 6.28 -command updatePlot
+
+set s 100.0
+set phi 0.5
+set chi 0.12
+set psi 0.0
+
+grid .s -sticky nsew
+grid .phi -sticky nsew
+grid .chi -sticky nsew
+grid .psi -sticky nsew
+grid .c -sticky nsew
+
+grid rowconfigure . 0 -weight 1
+grid columnconfigure . 0 -weight 1
+
+proc updatePlot {args} {
+	.c delete all
+	set width [winfo width .c]
+	set height [winfo height .c]
+	vexpr {
+		T = euler(::phi, ::chi, ::psi)
+		Tx = ::s*(T*::cube')'
+		x = Tx[:, 0]+width/2
+		y = -Tx[:, 1]+height/2
+	}
+	# create lines in the canvas
+	foreach {x1 x2} $x {y1 y2} $y {
+		.c create line [list $x1 $y1 $x2 $y2]
+	}
+}
+
+update; # let the geometry propagate
+updatePlot