From e7e99f52e9db96e1e9b77cf96b77f705e98cf70f Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sun, 26 Oct 2014 13:38:10 -0400
Subject: transform: Add transform-position procedure.

* sly/transform.scm (transform-position): New procedure.
---
 sly/transform.scm | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/sly/transform.scm b/sly/transform.scm
index 252c123..96b83e1 100644
--- a/sly/transform.scm
+++ b/sly/transform.scm
@@ -32,6 +32,7 @@
   #:export (make-transform null-transform identity-transform
             transform? transform-matrix
             transpose transform-vector2
+            transform-position
             transform+ transform*
             scale translate rotate-x rotate-y rotate-z rotate
             build-transform
@@ -101,6 +102,14 @@ column-major format."
                 (* y (array-ref m 1 1))
                 (array-ref m 1 3)))))
 
+(define (transform-position transform)
+  "Return a vector3 containing the positional data stored in
+TRANSFORM."
+  (let ((matrix (transform-matrix transform)))
+    (vector3 (array-ref matrix 3 0)
+             (array-ref matrix 3 1)
+             (array-ref matrix 3 2))))
+
 (define (transform+ . transforms)
   "Return the sum of all given transformation matrices.  Return
 null-transform if called without any arguments."
-- 
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