From b18c702f6d99a54a1cca4376ddc1f72e54633cd7 Mon Sep 17 00:00:00 2001
From: terencehill <piuntn@gmail.com>
Date: Fri, 10 Nov 2023 18:59:58 +0100
Subject: [PATCH] Allow negative values for the shot origin offset vector. This
 change reduces precision of the y and z components from 0.25 to 0.5

---
 qcsrc/common/util.qc | 45 ++++++++++++++++++++++++++++++++------------
 1 file changed, 33 insertions(+), 12 deletions(-)

diff --git a/qcsrc/common/util.qc b/qcsrc/common/util.qc
index df54e3536..c0ea0afea 100644
--- a/qcsrc/common/util.qc
+++ b/qcsrc/common/util.qc
@@ -1184,35 +1184,56 @@ vector get_shotvelocity(vector myvel, vector mydir, float spd, float newton_styl
 	return myvel + spd * mydir;
 }
 
+// compresses the shot origin offset vector to an int with the following format:
+// xxxxxxxx SSyyyyyy SUzzzzzz
+// 32109876 54321098 76543210
+// 1st byte: x component (it uses all 8 bits)
+// 2nd byte: y component in the last 6 bits and the signs of the x and y components
+// 3rd byte: z component in the last 6 bits and the sign of the z component (the 2nd bit is unused)
+// all values are doubled on compression and halved on decompression
+// so the precision for all components is 0.5
+// values are bound to the following ranges:
+// x: -127.5 +127.5
+// y:  -31.5  +31.5
+// z:  -31.5  +31.5
 float compressShotOrigin(vector v)
 {
-	float rx = rint(v.x * 2);
-	float ry = rint(v.y * 4) + 128;
-	float rz = rint(v.z * 4) + 128;
-	if(rx > 255 || rx < 0)
+	int rx_neg = (v.x < 0) ? 1 : 0;
+	int ry_neg = (v.y < 0) ? 1 : 0;
+	int rz_neg = (v.z < 0) ? 1 : 0;
+	int rx = rint(fabs(v.x) * 2);
+	int ry = rint(fabs(v.y) * 2);
+	int rz = rint(fabs(v.z) * 2);
+	if(rx > 255)
 	{
 		LOG_DEBUG("shot origin ", vtos(v), " x out of bounds\n");
 		rx = bound(0, rx, 255);
 	}
-	if(ry > 255 || ry < 0)
+	if(ry > 63)
 	{
 		LOG_DEBUG("shot origin ", vtos(v), " y out of bounds\n");
-		ry = bound(0, ry, 255);
+		ry = bound(0, ry, 63);
 	}
-	if(rz > 255 || rz < 0)
+	if(rz > 63)
 	{
 		LOG_DEBUG("shot origin ", vtos(v), " z out of bounds\n");
-		rz = bound(0, rz, 255);
+		rz = bound(0, rz, 63);
 	}
+	ry |= ry_neg * BIT(6) + rx_neg * BIT(7);
+	rz |= rz_neg * BIT(6); // BIT(7) unused
 	return rx * 0x10000 + ry * 0x100 + rz;
 }
 vector decompressShotOrigin(int f)
 {
 	vector v;
-	v.x = ((f & 0xFF0000) / 0x10000) / 2;
-	v.y = ((f & 0xFF00) / 0x100 - 128) / 4;
-	v.z = ((f & 0xFF) - 128) / 4;
-	return v;
+	v.x = f >> 16;
+	v.y = (f & 0xFF00) >> 8;
+	v.z = f & 0xFF;
+	// remove sign bits and apply sign
+	if (v.y & BIT(7)) { v.y &= ~BIT(7); v.x *= -1; }
+	if (v.y & BIT(6)) { v.y &= ~BIT(6); v.y *= -1; }
+	if (v.z & BIT(6)) { v.z &= ~BIT(6); v.z *= -1; }
+	return v / 2;
 }
 
 #ifdef GAMEQC
-- 
2.39.2