From cfbc1a447bba4e3648d9e15c1f776d6d8068951e Mon Sep 17 00:00:00 2001
From: gingerBill <bill@gingerbill.org>
Date: Thu, 20 Jan 2022 13:18:37 +0000
Subject: [PATCH] Correct inverse and inverse_transpose for 2x2 matrices

---
 core/runtime/core_builtin_matrix.odin | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/core/runtime/core_builtin_matrix.odin b/core/runtime/core_builtin_matrix.odin
index 08dca288e..53589587c 100644
--- a/core/runtime/core_builtin_matrix.odin
+++ b/core/runtime/core_builtin_matrix.odin
@@ -146,14 +146,14 @@ matrix2x2_inverse_transpose :: proc "contextless" (x: $M/matrix[2, 2]$T) -> (y:
 	d := x[0, 0]*x[1, 1] - x[0, 1]*x[1, 0]
 	when intrinsics.type_is_integer(T) {
 		y[0, 0] = +x[1, 1] / d
-		y[1, 0] = -x[1, 0] / d
-		y[0, 1] = -x[0, 1] / d
+		y[1, 0] = -x[0, 1] / d
+		y[0, 1] = -x[1, 0] / d
 		y[1, 1] = +x[0, 0] / d
 	} else {
 		id := 1 / d
 		y[0, 0] = +x[1, 1] * id
-		y[1, 0] = -x[1, 0] * id
-		y[0, 1] = -x[0, 1] * id
+		y[1, 0] = -x[0, 1] * id
+		y[0, 1] = -x[1, 0] * id
 		y[1, 1] = +x[0, 0] * id
 	}
 	return
@@ -214,16 +214,16 @@ matrix1x1_inverse :: proc "contextless" (x: $M/matrix[1, 1]$T) -> (y: M) {
 matrix2x2_inverse :: proc "contextless" (x: $M/matrix[2, 2]$T) -> (y: M) {
 	d := x[0, 0]*x[1, 1] - x[0, 1]*x[1, 0]
 	when intrinsics.type_is_integer(T) {
-		y[0, 0] = x[1, 1] / d
-		y[0, 1] = x[1, 0] / d
-		y[1, 0] = x[0, 1] / d
-		y[1, 1] = x[0, 0] / d
+		y[0, 0] = +x[1, 1] / d
+		y[0, 1] = -x[0, 1] / d
+		y[1, 0] = -x[1, 0] / d
+		y[1, 1] = +x[0, 0] / d
 	} else {
 		id := 1 / d
-		y[0, 0] = x[1, 1] * id
-		y[0, 1] = x[1, 0] * id
-		y[1, 0] = x[0, 1] * id
-		y[1, 1] = x[0, 0] * id
+		y[0, 0] = +x[1, 1] * id
+		y[0, 1] = -x[0, 1] * id
+		y[1, 0] = -x[1, 0] * id
+		y[1, 1] = +x[0, 0] * id
 	}
 	return
 }