1 files changed, 38 insertions, 17 deletions
diff --git a/engine/src/projection.rs b/engine/src/projection.rs
index 2191a93..b3bfa00 100644
--- a/engine/src/projection.rs
+++ b/engine/src/projection.rs
@@ -119,8 +119,6 @@ impl Orthographic
         clip_volume: ClipVolume,
     ) -> Matrix<f32, 4, 4>
     {
-        let mut result = Matrix::<f32, 4, 4>::new();
-
         let size = match self.size {
             OrthographicSize::FixedSize(fixed_size) => fixed_size,
             OrthographicSize::WindowSize => Dimens {
@@ -141,21 +139,10 @@ impl Orthographic
         let near = self.near;
         let far = self.far;
 
-        match clip_volume {
-            ClipVolume::NegOneToOne => {
-                result[MatrixCellPos { row: 0, col: 0 }] = 2.0 / (right - left);
-                result[MatrixCellPos { row: 1, col: 1 }] = 2.0 / (top - bottom);
-                result[MatrixCellPos { row: 2, col: 2 }] = -2.0 / (far - near);
-                result[MatrixCellPos { row: 0, col: 3 }] =
-                    -(right + left) / (right - left);
-                result[MatrixCellPos { row: 1, col: 3 }] =
-                    -(top + bottom) / (top - bottom);
-                result[MatrixCellPos { row: 2, col: 3 }] = -(far + near) / (far - near);
-                result[MatrixCellPos { row: 3, col: 3 }] = 1.0;
-            }
-        }
-
-        result
+        orthographic_rh(
+            OrthographicParams { left, right, bottom, top, near, far },
+            clip_volume,
+        )
     }
 }
 
@@ -187,3 +174,37 @@ pub enum ClipVolume
     /// -1 to +1. This is the OpenGL clip volume definition.
     NegOneToOne,
 }
+
+#[derive(Debug, Clone)]
+pub struct OrthographicParams
+{
+    pub left: f32,
+    pub right: f32,
+    pub bottom: f32,
+    pub top: f32,
+    pub near: f32,
+    pub far: f32,
+}
+
+/// Creates a orthographic projection matrix using right-handed coordinates.
+pub fn orthographic_rh(
+    OrthographicParams { left, right, bottom, top, near, far }: OrthographicParams,
+    clip_volume: ClipVolume,
+) -> Matrix<f32, 4, 4>
+{
+    let mut result = Matrix::<f32, 4, 4>::new();
+
+    match clip_volume {
+        ClipVolume::NegOneToOne => {
+            result[MatrixCellPos { row: 0, col: 0 }] = 2.0 / (right - left);
+            result[MatrixCellPos { row: 1, col: 1 }] = 2.0 / (top - bottom);
+            result[MatrixCellPos { row: 2, col: 2 }] = -2.0 / (far - near);
+            result[MatrixCellPos { row: 0, col: 3 }] = -(right + left) / (right - left);
+            result[MatrixCellPos { row: 1, col: 3 }] = -(top + bottom) / (top - bottom);
+            result[MatrixCellPos { row: 2, col: 3 }] = -(far + near) / (far - near);
+            result[MatrixCellPos { row: 3, col: 3 }] = 1.0;
+        }
+    }
+
+    result
+}