feat(engine): add cube mesh creation

2 files changed, 698 insertions, 0 deletions

diff --git a/engine/src/mesh.rs b/engine/src/mesh.rs
index e07ed35..de0af70 100644
--- a/engine/src/mesh.rs
+++ b/engine/src/mesh.rs
@@ -2,6 +2,8 @@ use ecs::Component;
 
 use crate::vertex::Vertex;
 
+pub mod cube;
+
 #[derive(Debug, Clone, Component)]
 pub struct Mesh
 {
diff --git a/engine/src/mesh/cube.rs b/engine/src/mesh/cube.rs
new file mode 100644
index 0000000..f00cf6d
--- /dev/null
+++ b/engine/src/mesh/cube.rs
@@ -0,0 +1,696 @@
+use crate::math::calc_triangle_surface_normal;
+use crate::mesh::Mesh;
+use crate::util::builder;
+use crate::vector::Vec3;
+use crate::vertex::{Builder as VertexBuilder, Vertex};
+
+builder! {
+/// Cube mesh creation specification.
+#[builder(name = CreationSpecBuilder, derives = (Debug, Default))]
+#[derive(Debug, Default)]
+#[non_exhaustive]
+pub struct CreationSpec
+{
+    pub width: f32,
+    pub height: f32,
+    pub depth: f32,
+}
+}
+
+impl CreationSpec
+{
+    /// Returns a new `CreationSpec` builder.
+    #[must_use]
+    pub fn builder() -> CreationSpecBuilder
+    {
+        CreationSpecBuilder::default()
+    }
+}
+
+#[derive(Debug)]
+pub enum Side
+{
+    Front,
+    Back,
+    Left,
+    Right,
+    Top,
+    Bottom,
+}
+
+#[derive(Debug)]
+pub enum Corner
+{
+    TopRight,
+    TopLeft,
+    BottomRight,
+    BottomLeft,
+}
+
+/// Creates a cube mesh.
+pub fn create(
+    creation_spec: CreationSpec,
+    vertex_builder_cb: impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+) -> Mesh
+{
+    let mut vertices: [Option<Vertex>; VertexIndex::VARIANT_CNT] =
+        [(); VertexIndex::VARIANT_CNT].map(|()| None);
+
+    create_front(&creation_spec, &mut vertices, &vertex_builder_cb);
+    create_back(&creation_spec, &mut vertices, &vertex_builder_cb);
+    create_right(&creation_spec, &mut vertices, &vertex_builder_cb);
+    create_left(&creation_spec, &mut vertices, &vertex_builder_cb);
+    create_top(&creation_spec, &mut vertices, &vertex_builder_cb);
+    create_bottom(&creation_spec, &mut vertices, &vertex_builder_cb);
+
+    let front = [
+        // 🮝
+        VertexIndex::FrontTopRight,
+        VertexIndex::FrontBottomRight,
+        VertexIndex::FrontTopLeft,
+        //
+        // 🮟
+        VertexIndex::FrontBottomRight,
+        VertexIndex::FrontBottomLeft,
+        VertexIndex::FrontTopLeft,
+    ];
+
+    let back = [
+        // 🮝
+        VertexIndex::BackTopRight,
+        VertexIndex::BackBottomRight,
+        VertexIndex::BackTopLeft,
+        //
+        // 🮟
+        VertexIndex::BackBottomRight,
+        VertexIndex::BackBottomLeft,
+        VertexIndex::BackTopLeft,
+    ];
+
+    let right = [
+        // 🮝
+        VertexIndex::RightBackTop,
+        VertexIndex::RightBackBottom,
+        VertexIndex::RightFrontTop,
+        //
+        // 🮟
+        VertexIndex::RightBackBottom,
+        VertexIndex::RightFrontBottom,
+        VertexIndex::RightFrontTop,
+    ];
+
+    let left = [
+        // 🮝
+        VertexIndex::LeftBackTop,
+        VertexIndex::LeftBackBottom,
+        VertexIndex::LeftFrontTop,
+        //
+        // 🮟
+        VertexIndex::LeftBackBottom,
+        VertexIndex::LeftFrontBottom,
+        VertexIndex::LeftFrontTop,
+    ];
+
+    let top = [
+        // 🮝
+        VertexIndex::TopBackRight,
+        VertexIndex::TopBackLeft,
+        VertexIndex::TopFrontRight,
+        //
+        // 🮟
+        VertexIndex::TopBackLeft,
+        VertexIndex::TopFrontLeft,
+        VertexIndex::TopFrontRight,
+    ];
+
+    let bottom = [
+        // 🮝
+        VertexIndex::BottomBackRight,
+        VertexIndex::BottomBackLeft,
+        VertexIndex::BottomFrontRight,
+        //
+        // 🮟
+        VertexIndex::BottomBackLeft,
+        VertexIndex::BottomFrontLeft,
+        VertexIndex::BottomFrontRight,
+    ];
+
+    let indices = [front, back, right, left, top, bottom];
+
+    Mesh::new(
+        vertices.map(Option::unwrap).to_vec(),
+        Some(
+            indices
+                .into_iter()
+                .flatten()
+                .map(|index| index as u32)
+                .collect(),
+        ),
+    )
+}
+
+macro_rules! one {
+    ($tt: tt) => {
+        1
+    };
+}
+
+macro_rules! enum_with_variant_cnt {
+    (
+        $(#[$attr: meta])*
+        enum $name: ident {
+            $($variant: ident,)*
+        }
+    ) => {
+        $(#[$attr])*
+        enum $name {
+            $($variant,)*
+        }
+
+        impl $name {
+            const VARIANT_CNT: usize = 0 $(+ one!($variant))*;
+        }
+    };
+}
+
+enum_with_variant_cnt! {
+#[repr(u32)]
+enum VertexIndex
+{
+    FrontTopRight,
+    FrontBottomRight,
+    FrontBottomLeft,
+    FrontTopLeft,
+
+    BackTopRight,
+    BackBottomRight,
+    BackBottomLeft,
+    BackTopLeft,
+
+    RightBackTop,
+    RightBackBottom,
+    RightFrontTop,
+    RightFrontBottom,
+
+    LeftBackTop,
+    LeftBackBottom,
+    LeftFrontTop,
+    LeftFrontBottom,
+
+    TopBackRight,
+    TopBackLeft,
+    TopFrontRight,
+    TopFrontLeft,
+
+    BottomBackRight,
+    BottomBackLeft,
+    BottomFrontRight,
+    BottomFrontLeft,
+}
+}
+
+fn create_front(
+    creation_spec: &CreationSpec,
+    vertices: &mut [Option<Vertex>],
+    vertex_builder_cb: &impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+)
+{
+    let front_top_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: creation_spec.height / 2.0,
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let front_bottom_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: -(creation_spec.height / 2.0),
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let front_bottom_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: -(creation_spec.height / 2.0),
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let front_top_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: creation_spec.height / 2.0,
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let front_normal = calc_triangle_surface_normal(
+        &front_top_right_pos,
+        &front_bottom_right_pos,
+        &front_top_left_pos,
+    );
+
+    vertices[VertexIndex::FrontTopRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(front_top_right_pos)
+                .normal(front_normal),
+            Side::Front,
+            Corner::TopRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::FrontBottomRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(front_bottom_right_pos)
+                .normal(front_normal),
+            Side::Front,
+            Corner::BottomRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::FrontBottomLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(front_bottom_left_pos)
+                .normal(front_normal),
+            Side::Front,
+            Corner::BottomLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::FrontTopLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(front_top_left_pos)
+                .normal(front_normal),
+            Side::Front,
+            Corner::TopLeft,
+        )
+        .build(),
+    );
+}
+
+fn create_back(
+    creation_spec: &CreationSpec,
+    vertices: &mut [Option<Vertex>],
+    vertex_builder_cb: &impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+)
+{
+    let back_top_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: creation_spec.height / 2.0,
+        z: creation_spec.depth / 2.0,
+    };
+
+    let back_bottom_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: -(creation_spec.height / 2.0),
+        z: creation_spec.depth / 2.0,
+    };
+
+    let back_bottom_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: -(creation_spec.height / 2.0),
+        z: creation_spec.depth / 2.0,
+    };
+
+    let back_top_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: creation_spec.height / 2.0,
+        z: creation_spec.depth / 2.0,
+    };
+
+    let back_normal = -calc_triangle_surface_normal(
+        &back_top_right_pos,
+        &back_bottom_right_pos,
+        &back_top_left_pos,
+    );
+
+    vertices[VertexIndex::BackTopRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(back_top_right_pos)
+                .normal(back_normal),
+            Side::Back,
+            Corner::TopRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::BackBottomRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(back_bottom_right_pos)
+                .normal(back_normal),
+            Side::Back,
+            Corner::BottomRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::BackBottomLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(back_bottom_left_pos)
+                .normal(back_normal),
+            Side::Back,
+            Corner::BottomLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::BackTopLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(back_top_left_pos)
+                .normal(back_normal),
+            Side::Back,
+            Corner::TopLeft,
+        )
+        .build(),
+    );
+}
+
+fn create_right(
+    creation_spec: &CreationSpec,
+    vertices: &mut [Option<Vertex>],
+    vertex_builder_cb: &impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+)
+{
+    let right_back_top_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: creation_spec.height / 2.0,
+        z: creation_spec.depth / 2.0,
+    };
+
+    let right_back_bottom_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: -(creation_spec.height / 2.0),
+        z: creation_spec.depth / 2.0,
+    };
+
+    let right_front_top_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: creation_spec.height / 2.0,
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let right_front_bottom_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: -(creation_spec.height / 2.0),
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let right_normal = calc_triangle_surface_normal(
+        &right_back_top_pos,
+        &right_back_bottom_pos,
+        &right_front_top_pos,
+    );
+
+    vertices[VertexIndex::RightBackTop as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(right_back_top_pos)
+                .normal(right_normal),
+            Side::Right,
+            Corner::TopLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::RightBackBottom as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(right_back_bottom_pos)
+                .normal(right_normal),
+            Side::Right,
+            Corner::BottomLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::RightFrontTop as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(right_front_top_pos)
+                .normal(right_normal),
+            Side::Right,
+            Corner::TopRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::RightFrontBottom as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(right_front_bottom_pos)
+                .normal(right_normal),
+            Side::Right,
+            Corner::BottomRight,
+        )
+        .build(),
+    );
+}
+
+fn create_left(
+    creation_spec: &CreationSpec,
+    vertices: &mut [Option<Vertex>],
+    vertex_builder_cb: &impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+)
+{
+    let left_back_top_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: creation_spec.height / 2.0,
+        z: creation_spec.depth / 2.0,
+    };
+
+    let left_back_bottom_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: -(creation_spec.height / 2.0),
+        z: creation_spec.depth / 2.0,
+    };
+
+    let left_front_top_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: creation_spec.height / 2.0,
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let left_front_bottom_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: -(creation_spec.height / 2.0),
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let left_normal = -calc_triangle_surface_normal(
+        &left_back_top_pos,
+        &left_back_bottom_pos,
+        &left_front_top_pos,
+    );
+
+    vertices[VertexIndex::LeftBackTop as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(left_back_top_pos)
+                .normal(left_normal),
+            Side::Left,
+            Corner::TopRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::LeftBackBottom as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(left_back_bottom_pos)
+                .normal(left_normal),
+            Side::Left,
+            Corner::BottomRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::LeftFrontTop as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(left_front_top_pos)
+                .normal(left_normal),
+            Side::Left,
+            Corner::TopLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::LeftFrontBottom as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(left_front_bottom_pos)
+                .normal(left_normal),
+            Side::Left,
+            Corner::BottomLeft,
+        )
+        .build(),
+    );
+}
+
+fn create_top(
+    creation_spec: &CreationSpec,
+    vertices: &mut [Option<Vertex>],
+    vertex_builder_cb: &impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+)
+{
+    let top_back_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: creation_spec.height / 2.0,
+        z: creation_spec.depth / 2.0,
+    };
+
+    let top_back_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: creation_spec.height / 2.0,
+        z: creation_spec.depth / 2.0,
+    };
+
+    let top_front_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: creation_spec.height / 2.0,
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let top_front_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: creation_spec.height / 2.0,
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let top_normal = -calc_triangle_surface_normal(
+        &top_back_right_pos,
+        &top_back_left_pos,
+        &top_front_right_pos,
+    );
+
+    vertices[VertexIndex::TopBackRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(top_back_right_pos)
+                .normal(top_normal),
+            Side::Top,
+            Corner::TopRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::TopBackLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(top_back_left_pos)
+                .normal(top_normal),
+            Side::Top,
+            Corner::TopLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::TopFrontLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(top_front_left_pos)
+                .normal(top_normal),
+            Side::Top,
+            Corner::BottomLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::TopFrontRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(top_front_right_pos)
+                .normal(top_normal),
+            Side::Top,
+            Corner::BottomRight,
+        )
+        .build(),
+    );
+}
+
+fn create_bottom(
+    creation_spec: &CreationSpec,
+    vertices: &mut [Option<Vertex>],
+    vertex_builder_cb: &impl Fn(VertexBuilder, Side, Corner) -> VertexBuilder,
+)
+{
+    let bottom_back_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: -(creation_spec.height / 2.0),
+        z: (creation_spec.depth / 2.0),
+    };
+
+    let bottom_back_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: -(creation_spec.height / 2.0),
+        z: creation_spec.depth / 2.0,
+    };
+
+    let bottom_front_right_pos = Vec3 {
+        x: creation_spec.width / 2.0,
+        y: -(creation_spec.height / 2.0),
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let bottom_front_left_pos = Vec3 {
+        x: -(creation_spec.width / 2.0),
+        y: -(creation_spec.height / 2.0),
+        z: -(creation_spec.depth / 2.0),
+    };
+
+    let bottom_normal = calc_triangle_surface_normal(
+        &bottom_back_right_pos,
+        &bottom_back_left_pos,
+        &bottom_front_right_pos,
+    );
+
+    vertices[VertexIndex::BottomBackRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(bottom_back_right_pos)
+                .normal(bottom_normal),
+            Side::Bottom,
+            Corner::BottomRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::BottomBackLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(bottom_back_left_pos)
+                .normal(bottom_normal),
+            Side::Bottom,
+            Corner::BottomLeft,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::BottomFrontRight as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(bottom_front_right_pos)
+                .normal(bottom_normal),
+            Side::Bottom,
+            Corner::TopRight,
+        )
+        .build(),
+    );
+
+    vertices[VertexIndex::BottomFrontLeft as usize] = Some(
+        vertex_builder_cb(
+            VertexBuilder::default()
+                .pos(bottom_front_left_pos)
+                .normal(bottom_normal),
+            Side::Bottom,
+            Corner::TopLeft,
+        )
+        .build(),
+    );
+}