Consolidate matrix construction API

citro3d/examples/triangle.rs

@@ -4,7 +4,7 @@
 #![feature(allocator_api)]
 
 use citro3d::macros::include_shader;
-use citro3d::math::{CoordinateSystem, Matrix};
+use citro3d::math::{ClipPlane, CoordinateSystem, Matrix, Orientation, Stereoscopic};
 use citro3d::render::{self, ClearFlags};
 use citro3d::{attrib, buffer, shader, AspectRatio};
 use ctru::prelude::*;
@@ -117,8 +117,8 @@ fn main() {
             };
 
             let Projections {
-                left,
-                right,
+                left_eye: left,
+                right_eye: right,
                 center,
             } = calculate_projections();
 
@@ -158,8 +158,8 @@ where
 }
 
 struct Projections {
-    left: Matrix,
-    right: Matrix,
+    left_eye: Matrix,
+    right_eye: Matrix,
     center: Matrix,
 }
 
@@ -167,44 +167,51 @@ fn calculate_projections() -> Projections {
     // TODO: it would be cool to allow playing around with these parameters on
     // the fly with D-pad, etc.
     let slider_val = unsafe { ctru_sys::osGet3DSliderState() };
-    let iod = slider_val / 4.0;
+    let interocular_distance = slider_val / 4.0;
 
-    let near = 0.01;
-    let far = 100.0;
-    let fov_y = 40.0_f32.to_radians();
-    let screen = 2.0;
+    let vertical_fov = 40.0_f32.to_radians();
+    let screen_depth = 2.0;
 
-    let left_eye = Matrix::perspective_stereo_tilt(
-        fov_y,
+    let clip_plane = ClipPlane {
+        near: 0.01,
+        far: 100.0,
+    };
+
+    let stereoscopic = Stereoscopic::Stereo {
+        interocular_distance,
+        screen_depth,
+    };
+
+    let left_eye = Matrix::perspective_projection(
+        vertical_fov,
         AspectRatio::TopScreen,
-        near,
-        far,
-        -iod,
-        screen,
+        Orientation::Natural,
+        clip_plane,
+        stereoscopic,
         CoordinateSystem::LeftHanded,
     );
 
-    let right_eye = Matrix::perspective_stereo_tilt(
-        fov_y,
+    let right_eye = Matrix::perspective_projection(
+        vertical_fov,
         AspectRatio::TopScreen,
-        near,
-        far,
-        iod,
-        screen,
+        Orientation::Natural,
+        clip_plane,
+        stereoscopic.invert(),
         CoordinateSystem::LeftHanded,
     );
 
-    let center = Matrix::perspective_tilt(
-        fov_y,
+    let center = Matrix::perspective_projection(
+        vertical_fov,
         AspectRatio::BottomScreen,
-        near,
-        far,
+        Orientation::Natural,
+        clip_plane,
+        Stereoscopic::Mono,
         CoordinateSystem::LeftHanded,
     );
 
     Projections {
-        left: left_eye,
-        right: right_eye,
+        left_eye,
+        right_eye,
         center,
     }
 }

citro3d/src/math.rs

@@ -16,67 +16,61 @@ pub struct Quaternion(citro3d_sys::C3D_FQuat);
 /// A 4x4 row-major matrix of `f32`s.
 pub struct Matrix(citro3d_sys::C3D_Mtx);
 
-/// Whether to use left-handed or right-handed coordinates for calculations.
-#[derive(Clone, Copy, Debug)]
-#[non_exhaustive] // This probably is exhaustive, but just in case
-pub enum CoordinateSystem {
-    LeftHanded,
-    RightHanded,
-}
-
 impl Matrix {
-    // TODO: this could probably be generalized with something like builder or options
-    // pattern. Should look and see what the different citro3d implementations look like
-    pub fn perspective_stereo_tilt(
-        fov_y: f32,
+    // TODO: does it make sense to have a helper that builds both left and right
+    // eyes for stereoscopic at the same time?
+
+    /// Construct a projection matrix suitable for projecting 3D world space onto
+    /// the 3DS screens.
+    pub fn perspective_projection(
+        vertical_fov: f32,
         aspect_ratio: AspectRatio,
-        near: f32,
-        far: f32,
-        interocular_distance: f32,
-        /* better name ?? */ screen_depth: f32,
+        orientation: Orientation,
+        clip_plane: ClipPlane,
+        stereo: Stereoscopic,
         coordinates: CoordinateSystem,
     ) -> Self {
-        let mut result = MaybeUninit::uninit();
-
-        let inner = unsafe {
-            citro3d_sys::Mtx_PerspStereoTilt(
-                result.as_mut_ptr(),
-                fov_y,
-                aspect_ratio.into(),
-                near,
-                far,
+        let (make_mtx_persp, make_mtx_stereo);
+
+        let initialize_mtx: &dyn Fn(_, _, _, _, _, _) -> _ = match stereo {
+            Stereoscopic::Mono => {
+                let make_mtx = match orientation {
+                    Orientation::Natural => citro3d_sys::Mtx_PerspTilt,
+                    Orientation::HardwareDefault => citro3d_sys::Mtx_Persp,
+                };
+
+                make_mtx_persp = move |a, b, c, d, e, f| unsafe { make_mtx(a, b, c, d, e, f) };
+                &make_mtx_persp
+            }
+            Stereoscopic::Stereo {
                 interocular_distance,
                 screen_depth,
-                matches!(coordinates, CoordinateSystem::LeftHanded),
-            );
-
-            result.assume_init()
+            } => {
+                let make_mtx = match orientation {
+                    Orientation::Natural => citro3d_sys::Mtx_PerspStereoTilt,
+                    Orientation::HardwareDefault => citro3d_sys::Mtx_PerspStereo,
+                };
+
+                make_mtx_stereo = move |a, b, c, d, e, f| unsafe {
+                    make_mtx(a, b, c, d, interocular_distance, screen_depth, e, f)
+                };
+                &make_mtx_stereo
+            }
         };
 
-        Self(inner)
-    }
+        let left_handed = matches!(coordinates, CoordinateSystem::LeftHanded);
 
-    pub fn perspective_tilt(
-        fov_y: f32,
-        aspect_ratio: AspectRatio,
-        near: f32,
-        far: f32,
-        coordinates: CoordinateSystem,
-    ) -> Self {
         let mut result = MaybeUninit::uninit();
+        initialize_mtx(
+            result.as_mut_ptr(),
+            vertical_fov,
+            aspect_ratio.into(),
+            clip_plane.near,
+            clip_plane.far,
+            left_handed,
+        );
 
-        let inner = unsafe {
-            citro3d_sys::Mtx_PerspTilt(
-                result.as_mut_ptr(),
-                fov_y,
-                aspect_ratio.into(),
-                near,
-                far,
-                matches!(coordinates, CoordinateSystem::LeftHanded),
-            );
-
-            result.assume_init()
-        };
+        let inner = unsafe { result.assume_init() };
 
         Self(inner)
     }
@@ -85,3 +79,56 @@ impl Matrix {
         &self.0
     }
 }
+
+/// Whether to use left-handed or right-handed coordinates for calculations.
+#[derive(Clone, Copy, Debug)]
+pub enum CoordinateSystem {
+    LeftHanded,
+    RightHanded,
+}
+
+/// Whether to rotate a projection to account for the 3DS screen configuration.
+/// Both screens on the 3DS are oriented such that the "top" of the screen is
+/// on the [left | right] ? side of the device when it's held normally, so
+/// projections must account for this extra rotation to display in the correct
+/// orientation.
+#[derive(Clone, Copy, Debug)]
+pub enum Orientation {
+    /// Rotate the projection 90° to account for the 3DS screen rotation.
+    Natural,
+    /// Don't rotate the projection at all.
+    HardwareDefault,
+}
+
+#[derive(Clone, Copy, Debug)]
+// TODO: better name
+pub enum Stereoscopic {
+    Mono,
+    Stereo {
+        interocular_distance: f32,
+        // TODO: better name? At least docstring
+        screen_depth: f32,
+    },
+}
+
+impl Stereoscopic {
+    /// Flip the stereoscopic projection for the opposite eye.
+    pub fn invert(self) -> Self {
+        match self {
+            Self::Stereo {
+                interocular_distance,
+                screen_depth,
+            } => Self::Stereo {
+                interocular_distance: -interocular_distance,
+                screen_depth,
+            },
+            mono => mono,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct ClipPlane {
+    pub near: f32,
+    pub far: f32,
+}