From: terencehill <piuntn@gmail.com>
Date: Sat, 11 Nov 2023 17:11:51 +0000 (+0100)
Subject: Don't allow negative values for the y component of the shot origin offset because... 
X-Git-Url: https://git.rm.cloudns.org/?a=commitdiff_plain;h=refs%2Fheads%2Fterencehill%2Fshotorigin_compression;p=xonotic%2Fxonotic-data.pk3dir.git

Don't allow negative values for the y component of the shot origin offset because the gun can't be aligned to the left by default. Thanks to this change it's possible to restore precision of the y and z components back to 0.25
---

diff --git a/qcsrc/common/util.qc b/qcsrc/common/util.qc
index c0ea0afea..1bb77a1f5 100644
--- a/qcsrc/common/util.qc
+++ b/qcsrc/common/util.qc
@@ -1184,43 +1184,44 @@ 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
+/*
+ * Compresses the shot origin offset vector to an int with the following format:
+ * xxxxxxxx|Syyyyyyy|Syzzzzzz
+ * 32109876|54321098|76543210
+ * 1st byte: x component
+ * 2nd byte: y component in the last 7 bits and the sign of the x component in the 1st bit
+ * 3rd byte: z component in the last 7 bits and the sign of the z component in the 1st bit
+ * All values are multiplied on compression and divided on decompression
+ * so the precision of the values is 0.5 if multiplied by 2 and 0.25 if multiplied by 4
+ * Values are bound to the following ranges:
+ * x: -127.5  +127.5
+ * y:      0  +31.75 negative values not allowed because the gun can't be aligned to the left by default
+ * z: -31.75  +31.75
+ */
 float compressShotOrigin(vector v)
 {
 	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)
+	int ry = rint(v.y * 4);
+	int rz = rint(fabs(v.z) * 4);
+	if(rx > 255) // 128 * 2 - 1
 	{
 		LOG_DEBUG("shot origin ", vtos(v), " x out of bounds\n");
 		rx = bound(0, rx, 255);
 	}
-	if(ry > 63)
+	if(ry > 127 || ry < 0) // 32 * 4 - 1
 	{
 		LOG_DEBUG("shot origin ", vtos(v), " y out of bounds\n");
-		ry = bound(0, ry, 63);
+		ry = bound(0, ry, 127);
 	}
-	if(rz > 63)
+	if(rz > 127) // 32 * 4 - 1
 	{
 		LOG_DEBUG("shot origin ", vtos(v), " z out of bounds\n");
-		rz = bound(0, rz, 63);
+		rz = bound(0, rz, 127);
 	}
-	ry |= ry_neg * BIT(6) + rx_neg * BIT(7);
-	rz |= rz_neg * BIT(6); // BIT(7) unused
+	ry |= rx_neg * BIT(7);
+	rz |= rz_neg * BIT(7);
 	return rx * 0x10000 + ry * 0x100 + rz;
 }
 vector decompressShotOrigin(int f)
@@ -1231,9 +1232,8 @@ vector decompressShotOrigin(int f)
 	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;
+	if (v.z & BIT(7)) { v.z &= ~BIT(7); v.z *= -1; }
+	return vec3(v.x / 2, v.y / 4, v.z / 4);
 }
 
 #ifdef GAMEQC