From 565bf0e96750588e8a7f6816e79683e97896f8de Mon Sep 17 00:00:00 2001
From: Matthew Stewart
Date: Thu, 19 Jul 2018 04:39:57 -0400
Subject: STARTREK: atan2 function

---
 engines/startrek/math.cpp | 129 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 engines/startrek/math.cpp

(limited to 'engines/startrek/math.cpp')

diff --git a/engines/startrek/math.cpp b/engines/startrek/math.cpp
new file mode 100644
index 0000000000..80aa39ee6a
--- /dev/null
+++ b/engines/startrek/math.cpp
@@ -0,0 +1,129 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "startrek/startrek.h"
+
+namespace StarTrek {
+
+Fixed14 StarTrekEngine::sin(Fixed8 angle) {
+	int16 i = angle.raw();
+	if (angle < 0) {
+		i %= 0x400;
+		i += 0x400;
+	}
+	i &= 0x3ff;
+
+	if (i == 0x100)
+		return 1.0;
+	else if (i == 0x300)
+		return -1.0;
+
+	float f;
+	if (i < 0x100)
+		f = _sineTable.getTable()[i & 0xff];
+	else if (i < 0x200)
+		f = _sineTable.getTable()[256 - (i & 0xff)];
+	else if (i < 0x300)
+		f = -_sineTable.getTable()[i & 0xff];
+	else if (i < 0x400)
+		f = -_sineTable.getTable()[256 - (i & 0xff)];
+	return Fixed16(f);
+}
+
+Fixed14 StarTrekEngine::cos(Fixed8 angle) {
+	return sin(angle + 1.0);
+}
+
+Fixed8 StarTrekEngine::atan2(int32 deltaX, int32 deltaY) {
+	const int16 atanTable[] = {
+		0x0000, 0x0064, 0x00c9, 0x012d, 0x0192, 0x01f6, 0x025b, 0x02c0,
+		0x0324, 0x0389, 0x03ee, 0x0453, 0x04b8, 0x051d, 0x0582, 0x05e8,
+		0x064d, 0x06b3, 0x0718, 0x077e, 0x07e4, 0x084a, 0x08b1, 0x0917,
+		0x097e, 0x09e5, 0x0a4c, 0x0ab3, 0x0b1a, 0x0b82, 0x0bea, 0x0c52,
+		0x0cba, 0x0d23, 0x0d8c, 0x0df5, 0x0e5f, 0x0ec8, 0x0f32, 0x0f9d,
+		0x1007, 0x1072, 0x10de, 0x114a, 0x11b6, 0x1222, 0x128f, 0x12fc,
+		0x136a, 0x13d8, 0x1446, 0x14b5, 0x1524, 0x1594, 0x1604, 0x1675,
+		0x16e6, 0x1757, 0x17ca, 0x183c, 0x18b0, 0x1923, 0x1998, 0x1a0c,
+		0x1a82, 0x1af8, 0x1b6f, 0x1be6, 0x1c5e, 0x1cd7, 0x1d50, 0x1dca,
+		0x1e45, 0x1ec0, 0x1f3c, 0x1fb9, 0x2037, 0x20b5, 0x2134, 0x21b4,
+		0x2235, 0x22b7, 0x2339, 0x23bd, 0x2441, 0x24c6, 0x254c, 0x25d4,
+		0x265c, 0x26e5, 0x276f, 0x27fa, 0x2887, 0x2914, 0x29a2, 0x2a32,
+		0x2ac3, 0x2b55, 0x2be8, 0x2c7d, 0x2d12, 0x2da9, 0x2e42, 0x2edc,
+		0x2f77, 0x3013, 0x30b1, 0x3151, 0x31f2, 0x3294, 0x3338, 0x33de,
+		0x3486, 0x352f, 0x35d9, 0x3686, 0x3734, 0x37e5, 0x3897, 0x394b,
+		0x3a01, 0x3ab9, 0x3b73, 0x3c30, 0x3cee, 0x3daf, 0x3e72, 0x3f38,
+		0x4000
+	};
+
+	if (deltaX == 0 && deltaY == 0)
+		return 0.0;
+
+	bool deltaYNegative = deltaY <= 0;
+	bool deltaXNegative = deltaX <= 0;
+
+	deltaY = abs(deltaY);
+	deltaX = abs(deltaX);
+
+	Fixed14 ratio;
+	if (deltaY > deltaX)
+		ratio = Fixed14::fromRaw(((deltaX & 0xffff0000) >> 2) / (deltaY >> 16));
+	else
+		ratio = Fixed14::fromRaw(((deltaY & 0xffff0000) >> 2) / (deltaX >> 16));
+
+	int16 endIndex = 128;
+	int16 index = 0;
+	int16 angle;
+	while (index <= endIndex) {
+		angle = (index + endIndex) / 2;
+		Fixed14 tableValue = Fixed14::fromRaw(atanTable[angle]);
+		if (tableValue > ratio)
+			endIndex = angle - 1;
+		else if (tableValue < ratio)
+			index = angle + 1;
+		else
+			break;
+	}
+
+	if (deltaY > deltaX) {
+		if (!deltaYNegative && !deltaXNegative)
+			angle = angle;
+		else if (!deltaYNegative && deltaXNegative)
+			angle = -angle;
+		else if (deltaYNegative && !deltaXNegative)
+			angle = 512 - angle;
+		else
+			angle = angle - 512;
+	} else {
+		if (!deltaYNegative && !deltaXNegative)
+			angle = 256 - angle;
+		else if (deltaYNegative && !deltaXNegative)
+			angle = 256 + angle;
+		else if (deltaYNegative && deltaXNegative)
+			angle = -256 - angle;
+		else
+			angle = -256 + angle;
+	}
+
+	return Fixed8::fromRaw(angle);
+}
+
+}
-- 
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