From 63174b401dd2bf1e43ef1db56868347921b8596b Mon Sep 17 00:00:00 2001
From: water111 <48171810+water111@users.noreply.github.com>
Date: Wed, 1 Jun 2022 19:48:48 -0400
Subject: [PATCH] [game] prevent NaNs when there's a zero area triangle in
 edgegrab (#1404)

---
 game/mips2c/functions/collide_edge_grab.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/game/mips2c/functions/collide_edge_grab.cpp b/game/mips2c/functions/collide_edge_grab.cpp
index e5e6a7b468..82969343e2 100644
--- a/game/mips2c/functions/collide_edge_grab.cpp
+++ b/game/mips2c/functions/collide_edge_grab.cpp
@@ -104,6 +104,12 @@ u64 execute(void* ctxt) {
   c->vmadd_bc(DEST::w, BC::z, vf9, vf0, vf9);       // vmaddz.w vf9, vf0, vf9
   // nop                                            // sll r0, r0, 0
   c->vrsqrt(vf0, BC::w, vf9, BC::w);                // vrsqrt Q, vf0.w, vf9.w
+  if (c->vfs[vf9].f[3] == 0.f) {
+    // hack to prevent NaNs from getting in the collide data if we have a zero-area triangle
+    // this value doesn't matter - the normal is zeros anyway and the triangle will be rejected
+    // by every other step.
+    c->Q = 0.f;
+  }
   // nop                                            // sll r0, r0, 0
   c->dsll32(t5, t5, 12);                            // dsll32 t5, t5, 12
   c->dsrl32(t5, t5, 26);                            // dsrl32 t5, t5, 26