feat(engine): add simple collision

1 files changed, 142 insertions, 0 deletions

diff --git a/engine/src/collision.rs b/engine/src/collision.rs
new file mode 100644
index 0000000..aefd9b6
--- /dev/null
+++ b/engine/src/collision.rs
@@ -0,0 +1,142 @@
+use ecs::Component;
+
+use crate::mesh::Mesh;
+use crate::vector::Vec3;
+
+pub trait Collider<Other>
+{
+    fn intersects(&self, other: &Other) -> bool;
+}
+
+#[derive(Debug, Default, Clone, Component)]
+#[non_exhaustive]
+pub struct BoxCollider
+{
+    pub min: Vec3<f32>,
+    pub max: Vec3<f32>,
+}
+
+impl BoxCollider
+{
+    pub fn for_mesh(mesh: &Mesh) -> Self
+    {
+        let furthest_dir_points = mesh.find_furthest_vertex_positions();
+
+        Self {
+            min: Vec3 {
+                x: furthest_dir_points.left.x,
+                y: furthest_dir_points.down.y,
+                z: furthest_dir_points.back.z,
+            },
+            max: Vec3 {
+                x: furthest_dir_points.right.x,
+                y: furthest_dir_points.up.y,
+                z: furthest_dir_points.front.z,
+            },
+        }
+    }
+
+    pub fn offset(self, offset: Vec3<f32>) -> Self
+    {
+        Self {
+            min: self.min + offset,
+            max: self.max + offset,
+        }
+    }
+}
+
+impl Collider<BoxCollider> for BoxCollider
+{
+    fn intersects(&self, other: &BoxCollider) -> bool
+    {
+        self.min.x <= other.max.x
+            && self.max.x >= other.min.x
+            && self.min.y <= other.max.y
+            && self.max.y >= other.min.y
+            && self.min.z <= other.max.z
+            && self.max.z >= other.min.z
+    }
+}
+
+impl Collider<SphereCollider> for BoxCollider
+{
+    fn intersects(&self, other: &SphereCollider) -> bool
+    {
+        other.intersects(self)
+    }
+}
+
+impl Collider<Vec3<f32>> for BoxCollider
+{
+    fn intersects(&self, other: &Vec3<f32>) -> bool
+    {
+        other.x >= self.min.x
+            && other.y >= self.min.y
+            && other.z >= self.min.z
+            && other.x <= self.max.x
+            && other.y <= self.max.y
+            && other.z <= self.max.z
+    }
+}
+
+#[derive(Debug, Default, Clone, Component)]
+pub struct SphereCollider
+{
+    pub center: Vec3<f32>,
+    pub radius: f32,
+}
+
+impl SphereCollider
+{
+    pub fn offset(self, offset: Vec3<f32>) -> Self
+    {
+        Self {
+            center: self.center + offset,
+            radius: self.radius,
+        }
+    }
+}
+
+impl Collider<SphereCollider> for SphereCollider
+{
+    fn intersects(&self, other: &SphereCollider) -> bool
+    {
+        (&self.center - &other.center).length() <= self.radius + other.radius
+    }
+}
+
+impl Collider<BoxCollider> for SphereCollider
+{
+    fn intersects(&self, other: &BoxCollider) -> bool
+    {
+        let mut min_distance = 0.0;
+
+        if self.center.x < other.min.x {
+            min_distance += (self.center.x - other.min.x).powf(2.0);
+        } else if self.center.x > other.max.x {
+            min_distance += (self.center.x - other.max.x).powf(2.0);
+        }
+
+        if self.center.y < other.min.y {
+            min_distance += (self.center.y - other.min.y).powf(2.0);
+        } else if self.center.y > other.max.y {
+            min_distance += (self.center.y - other.max.y).powf(2.0);
+        }
+
+        if self.center.z < other.min.z {
+            min_distance += (self.center.z - other.min.z).powf(2.0);
+        } else if self.center.z > other.max.z {
+            min_distance += (self.center.z - other.max.z).powf(2.0);
+        }
+
+        min_distance <= self.radius.powf(2.0)
+    }
+}
+
+impl Collider<Vec3<f32>> for SphereCollider
+{
+    fn intersects(&self, other: &Vec3<f32>) -> bool
+    {
+        (&self.center - other).length() <= self.radius
+    }
+}