From: bones_was_here <bones_was_here@xonotic.au>
Date: Wed, 22 Jan 2025 18:18:10 +0000 (+1000)
Subject: Match Q3 wishspeed and wishdir calculations
X-Git-Url: https://git.rm.cloudns.org/?a=commitdiff_plain;h=f671ff556dc561fd81bc6f31039a5c37333a948b;p=xonotic%2Fxonotic-data.pk3dir.git

Match Q3 wishspeed and wishdir calculations

This is equivalent to the relevant change in
0e542a1e3052b8bfe744b6ab34fe62de005b379d and produces the same pipeline
hash (ie the same hash as given by reverting
bec7b1df67bdb738bd65cdb261fe4e6a30890073).

It's written `wishvel * (1 / wishspeed)` because that's how Q3 does it.
The difference in the result is insignificant for normal gametypes but
might be significant for Q3 DeFRaG compatibility in extreme cases.

See https://gitlab.com/xonotic/xonotic-data.pk3dir/-/merge_requests/1438
for discussion.
---

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 037245249..c94fcbfe5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -45,7 +45,7 @@ test_compilation_units:
 test_sv_game:
   stage: test
   script:
-    - export EXPECT=5a343412b4fa7772695453d4dd0d03a7
+    - export EXPECT=601b58ab0baed5060eb18c8fc084e072
     - qcsrc/tools/sv_game-hashtest.sh
     - exit $?
 
diff --git a/qcsrc/ecs/systems/physics.qc b/qcsrc/ecs/systems/physics.qc
index cfa927b8e..da2000c21 100644
--- a/qcsrc/ecs/systems/physics.qc
+++ b/qcsrc/ecs/systems/physics.qc
@@ -266,8 +266,11 @@ void sys_phys_simulate(entity this, float dt)
 	}
 
 	// acceleration
-	const vector wishdir = normalize(wishvel);
-	float wishspeed = min(vlen(wishvel), this.com_phys_vel_max);
+	float wishspeed = vlen(wishvel);
+	// Mathematically equivalent to normalize(wishvel) but more closely matches Q3
+	// which uses the same single-precision optimisation to save one sqrt()
+	const vector wishdir = wishspeed ? wishvel * (1 / wishspeed) : '0 0 0';
+	wishspeed = min(wishspeed, this.com_phys_vel_max);
 
 	if (this.com_phys_air) {
 		if (!(this.flags & FL_WATERJUMP)) {