rendering, physics, player and camera WIP

src/picking.rs

@@ -0,0 +1,87 @@
+use crate::camera::Camera;
+use crate::mesh::Mesh;
+use glam::{Mat4, Vec3, Vec4};
+
+pub struct Ray
+{
+    pub origin: Vec3,
+    pub direction: Vec3,
+}
+
+impl Ray
+{
+    pub fn from_screen_position(
+        screen_x: f32,
+        screen_y: f32,
+        screen_width: u32,
+        screen_height: u32,
+        camera: &Camera,
+    ) -> Self
+    {
+        let ndc_x = (2.0 * screen_x) / screen_width as f32 - 1.0;
+        let ndc_y = 1.0 - (2.0 * screen_y) / screen_height as f32;
+
+        let clip_coords = Vec4::new(ndc_x, ndc_y, -1.0, 1.0);
+
+        let view_matrix = camera.view_matrix();
+        let projection_matrix = camera.projection_matrix();
+        let inv_projection = projection_matrix.inverse();
+        let inv_view = view_matrix.inverse();
+
+        let eye_coords = inv_projection * clip_coords;
+        let eye_coords = Vec4::new(eye_coords.x, eye_coords.y, -1.0, 0.0);
+
+        let world_coords = inv_view * eye_coords;
+        let direction = Vec3::new(world_coords.x, world_coords.y, world_coords.z).normalize();
+
+        Ray {
+            origin: camera.position,
+            direction,
+        }
+    }
+
+    pub fn intersects_mesh(&self, mesh: &Mesh, transform: &Mat4) -> Option<f32>
+    {
+        let inv_transform = transform.inverse();
+        let local_origin = inv_transform.transform_point3(self.origin);
+        let local_direction = inv_transform.transform_vector3(self.direction).normalize();
+
+        let mut closest_distance = f32::MAX;
+        let mut hit = false;
+
+        for triangle_idx in (0..mesh.num_indices).step_by(3)
+        {
+            let distance =
+                self.intersects_triangle_local(local_origin, local_direction, mesh, triangle_idx);
+
+            if let Some(d) = distance
+            {
+                if d < closest_distance
+                {
+                    closest_distance = d;
+                    hit = true;
+                }
+            }
+        }
+
+        if hit
+        {
+            Some(closest_distance)
+        }
+        else
+        {
+            None
+        }
+    }
+
+    fn intersects_triangle_local(
+        &self,
+        local_origin: Vec3,
+        local_direction: Vec3,
+        _mesh: &Mesh,
+        _triangle_idx: u32,
+    ) -> Option<f32>
+    {
+        None
+    }
+}