feat(engine): add orthographic projection support

1 files changed, 92 insertions, 19 deletions

diff --git a/engine/src/projection.rs b/engine/src/projection.rs
index aa84a9f..ecbe297 100644
--- a/engine/src/projection.rs
+++ b/engine/src/projection.rs
@@ -1,10 +1,14 @@
+use crate::data_types::dimens::Dimens3;
 use crate::matrix::Matrix;
+use crate::util::builder;
+use crate::vector::Vec3;
 
 #[derive(Debug)]
 #[non_exhaustive]
 pub enum Projection
 {
     Perspective(Perspective),
+    Orthographic(Orthographic),
 }
 
 /// Perspective projection parameters.
@@ -16,6 +20,22 @@ pub struct Perspective
     pub near: f32,
 }
 
+impl Perspective
+{
+    pub fn to_matrix(&self, aspect: f32) -> Matrix<f32, 4, 4>
+    {
+        let mut out = Matrix::new();
+
+        out.set_cell(0, 0, (1.0 / (self.fov_radians / 2.0).tan()) / aspect);
+        out.set_cell(1, 1, 1.0 / (self.fov_radians / 2.0).tan());
+        out.set_cell(2, 2, (self.near + self.far) / (self.near - self.far));
+        out.set_cell(2, 3, (2.0 * self.near * self.far) / (self.near - self.far));
+        out.set_cell(3, 2, -1.0);
+
+        out
+    }
+}
+
 impl Default for Perspective
 {
     fn default() -> Self
@@ -28,30 +48,83 @@ impl Default for Perspective
     }
 }
 
-pub(crate) fn new_perspective_matrix(
-    perspective: &Perspective,
-    aspect: f32,
-) -> Matrix<f32, 4, 4>
+builder! {
+#[builder(name = OrthographicBuilder, derives=(Debug, Clone))]
+#[derive(Debug, Clone, PartialEq, PartialOrd)]
+#[non_exhaustive]
+pub struct Orthographic
 {
-    let mut out = Matrix::new();
+    pub size: Dimens3<f32>,
+}
+}
+
+impl Orthographic
+{
+    pub fn builder() -> OrthographicBuilder
+    {
+        OrthographicBuilder::default()
+    }
+
+    /// Creates a orthographic projection matrix using right-handed coordinates.
+    pub fn to_matrix_rh(
+        &self,
+        center_pos: &Vec3<f32>,
+        clip_volume: ClipVolume,
+    ) -> Matrix<f32, 4, 4>
+    {
+        let mut result = Matrix::<f32, 4, 4>::new();
+
+        let left = center_pos.x - (self.size.width / 2.0);
+        let right = center_pos.x + (self.size.width / 2.0);
+        let bottom = center_pos.y - (self.size.height / 2.0);
+        let top = center_pos.y + (self.size.height / 2.0);
+        let near = center_pos.z - (self.size.depth / 2.0);
+        let far = center_pos.z + (self.size.depth / 2.0);
 
-    out.set_cell(0, 0, (1.0 / (perspective.fov_radians / 2.0).tan()) / aspect);
+        match clip_volume {
+            ClipVolume::NegOneToOne => {
+                result.set_cell(0, 0, 2.0 / (right - left));
+                result.set_cell(1, 1, 2.0 / (top - bottom));
+                result.set_cell(2, 2, -2.0 / (far - near));
+                result.set_cell(0, 3, -(right + left) / (right - left));
+                result.set_cell(1, 3, -(top + bottom) / (top - bottom));
+                result.set_cell(2, 3, -(far + near) / (far - near));
+                result.set_cell(3, 3, 1.0);
+            }
+        }
 
-    out.set_cell(1, 1, 1.0 / (perspective.fov_radians / 2.0).tan());
+        result
+    }
+}
 
-    out.set_cell(
-        2,
-        2,
-        (perspective.near + perspective.far) / (perspective.near - perspective.far),
-    );
+impl Default for Orthographic
+{
+    fn default() -> Self
+    {
+        Self {
+            size: Dimens3 {
+                width: 10.0,
+                height: 7.0,
+                depth: 10.0,
+            },
+        }
+    }
+}
 
-    out.set_cell(
-        2,
-        3,
-        (2.0 * perspective.near * perspective.far) / (perspective.near - perspective.far),
-    );
+impl Default for OrthographicBuilder
+{
+    fn default() -> Self
+    {
+        let orthographic = Orthographic::default();
 
-    out.set_cell(3, 2, -1.0);
+        OrthographicBuilder { size: orthographic.size }
+    }
+}
 
-    out
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[non_exhaustive]
+pub enum ClipVolume
+{
+    /// -1 to +1. This is the OpenGL clip volume definition.
+    NegOneToOne,
 }