feat: add vec3 to stem

packages/utils/src/geometry/geometry.rs

@@ -0,0 +1,74 @@
+use crate::log;
+
+pub struct GeometryData<'a> {
+    pub positions: &'a mut [f32], // View into `data`
+    pub normals: &'a mut [f32],   // View into `data`
+    pub faces: &'a mut [i32],     // View into `data`
+}
+
+pub fn create_geometry_data(vertex_amount: usize, face_amount: usize) -> Vec<i32> {
+    let amount = 3 // definition (type, vertex_amount, face_amount)
+      + 4 // opening and closing brackets
+      + vertex_amount * 3  // positions
+      + vertex_amount * 3  // normals
+      + face_amount * 3; // faces
+
+    let mut geo = vec![0; amount];
+
+    geo[0] = 0; // opening bracket
+    geo[1] = amount as i32 - 2; // opening bracket
+    geo[2] = 1; // type: geometry
+    geo[3] = vertex_amount as i32;
+    geo[4] = face_amount as i32;
+    geo[amount - 2] = 1; // closing bracket
+    geo[amount - 1] = 1; // closing bracket
+
+    geo
+}
+
+pub fn wrap_geometry_data(geometry: &mut [i32]) -> GeometryData {
+    // Basic validity checks
+    assert!(
+        geometry.len() > 5,
+        "Geometry vector does not contain enough data for a header."
+    );
+
+    // Split at after header
+    let (header, rest) = geometry.split_at_mut(5);
+
+    let vertices_amount = header[3] as usize;
+    let face_amount = header[4] as usize;
+    let total_floats = vertices_amount * 3 * 2;
+
+    let (faces, rest) = rest.split_at_mut(face_amount * 3);
+    let (positions_slice, rest) = rest.split_at_mut(vertices_amount * 3);
+    let (normals_slice, _) = rest.split_at_mut(vertices_amount * 3);
+
+    log!(
+        "Vertices: {}, normals: {}, Total floats: {}",
+        positions_slice.len(),
+        normals_slice.len(),
+        total_floats
+    );
+
+    assert!(
+        positions_slice.len() + normals_slice.len() == total_floats,
+        "Slices do not match the expected sizes."
+    );
+
+    let positions: &mut [f32] = unsafe {
+        std::slice::from_raw_parts_mut(
+            positions_slice.as_mut_ptr() as *mut f32,
+            positions_slice.len(),
+        )
+    };
+    let normals: &mut [f32] = unsafe {
+        std::slice::from_raw_parts_mut(normals_slice.as_mut_ptr() as *mut f32, normals_slice.len())
+    };
+
+    GeometryData {
+        positions,
+        normals,
+        faces,
+    }
+}