From 0fffa641de8e14a14c6079fcf853f9d5532b2302 Mon Sep 17 00:00:00 2001
From: fredrikr79 <fredrikrobertsen7@gmail.com>
Date: Wed, 3 Sep 2025 14:25:33 +0200
Subject: [PATCH] vertex shader: mirror vertices over x- and y-axes

---
 gloom-rs/shaders/simple.vert | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/gloom-rs/shaders/simple.vert b/gloom-rs/shaders/simple.vert
index 5bf2e12..804d4eb 100644
--- a/gloom-rs/shaders/simple.vert
+++ b/gloom-rs/shaders/simple.vert
@@ -2,7 +2,15 @@
 
 in vec3 position;
 
+// this matrix mirrors over the x-axis and the y-axis simultaneously
+uniform mat4 flip = mat4(
+    vec4(-1.0f,  0.0f,  0.0f,  0.0f),  // column 0
+    vec4( 0.0f, -1.0f,  0.0f,  0.0f),  // column 1
+    vec4( 0.0f,  0.0f,  1.0f,  0.0f),  // column 2
+    vec4( 0.0f,  0.0f,  0.0f,  1.0f)   // column 3
+);
+
 void main()
 {
-    gl_Position = vec4(position, 1.0f);
-}
\ No newline at end of file
+    gl_Position = flip * vec4(position, 1.0f);
+}