From 2b86c2ba0074afe2eff0cfeb5cb1b18ca9984834 Mon Sep 17 00:00:00 2001
From: Lars-Dominik Braun <lars@6xq.net>
Date: Sun, 22 Mar 2015 11:17:44 +0100
Subject: Use camera transform matrix

Rotation and camera transformation are a single matrix now. Speedup is
negligible (~1%, depending on #xforms).
---
 math.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

(limited to 'math.h')

diff --git a/math.h b/math.h
index fa49d09..d6e3211 100644
--- a/math.h
+++ b/math.h
@@ -27,6 +27,7 @@
 #define REPLACE_WITH_AMDLIBM
 #include <amdlibm.h>
 #undef nearbyint
+#undef floor
 #endif
 
 #define clamp(a,min,max) (a > max ? max : (a < min ? min : a))
@@ -55,6 +56,14 @@ inline void translate (const double2 xy, double2 matrix[3]) {
 	matrix[2] = xy;
 }
 
+/*	Create affine scaling matrix
+ */
+inline void scale (const double2 xy, double2 matrix[3]) {
+	matrix[0] = (double2) { xy[0], 0.0 };
+	matrix[1] = (double2) { 0.0, xy[1] };
+	matrix[2] = (double2) { 0.0, 0.0 };
+}
+
 /*	Multiply two affine matrices a, b and store the result in c.
  *
  *	The last row of each matrix is assumed to be 0, 0, 1.
@@ -65,6 +74,23 @@ inline void matrixmul (const double2 a[3], const double2 b[3], double2 c[3]) {
 	c[2] = a[0] * b[2][0] + a[1] * b[2][1] + a[2];
 }
 
+/*	Affine matrix that transforms rect from (x1, y1, x2, y2) into rect to
+ */
+inline void translate_rect (const double4 from, const double4 to,
+		double2 matrix[3]) {
+	const double2 from_edge = (double2) { from[0], from[1] },
+			to_edge = (double2) { to[0], to[1] };
+	/* first align one of A and B’s edges */
+	double2 translate_edge[3];
+	translate (to_edge - from_edge, translate_edge);
+	/* then scale it up or down */
+	double2 scale_rect[3];
+	scale ((double2) { (to[2] - to[0])/(from[2] - from[0]),
+			(to[3] - to[1])/(from[3] - from[1])}, scale_rect);
+	/* the result is scale*translate (i.e. translate first) */
+	matrixmul (scale_rect, translate_edge, matrix);
+}
+
 /* Create rotation around center. Note that matrix multiplication is
  * right-associative, thus A*B*C == A*(B*C) */
 inline void rotate_center (const double2 center, const double angle, double2 out[3]) {
-- 
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