feat: add model matrix transforms and set tail rotor reference point for scene nodes

src/main.rs

@@ -129,16 +129,29 @@ unsafe fn create_vao(vertices: &Vec<f32>, normals: &Vec<f32>, colors: &Vec<f32>,
 
 // Scene graph drawing function
 unsafe fn draw_scene(node: &scene_graph::SceneNode, transform_loc: i32, view_projection: &glm::Mat4, transform_so_far: &glm::Mat4) {
+    // Build model matrix from node transformations
+    let translation = glm::translation(&node.position);
+    let rot_x = glm::rotation(node.rotation.x, &glm::vec3(1.0, 0.0, 0.0));
+    let rot_y = glm::rotation(node.rotation.y, &glm::vec3(0.0, 1.0, 0.0));
+    let rot_z = glm::rotation(node.rotation.z, &glm::vec3(0.0, 0.0, 1.0));
+    let rotation = rot_z * rot_y * rot_x;
+    let scaling = glm::scaling(&node.scale);
+    let refp = node.reference_point;
+    let to_ref = glm::translation(&refp);
+    let from_ref = glm::translation(&-refp);
+    let model = translation * to_ref * rotation * scaling * from_ref;
+    let new_transform = *transform_so_far * model;
+
     // Draw this node if drawable
     if node.index_count > 0 {
-        let model_transform = view_projection * *transform_so_far;
-        gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, model_transform.as_ptr());
+        let mvp = view_projection * new_transform;
+        gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, mvp.as_ptr());
         gl::BindVertexArray(node.vao_id);
         gl::DrawElements(gl::TRIANGLES, node.index_count, gl::UNSIGNED_INT, ptr::null());
     }
     // Recurse to children
     for &child in &node.children {
-        draw_scene(&*child, transform_loc, view_projection, transform_so_far);
+        draw_scene(&*child, transform_loc, view_projection, &new_transform);
     }
 }
 
@@ -232,7 +245,10 @@ fn main() {
         let body_node       = SceneNode::from_vao(heli_body_vao, helicopter.body.index_count);
         let door_node       = SceneNode::from_vao(heli_door_vao, helicopter.door.index_count);
         let main_rotor_node = SceneNode::from_vao(heli_main_rotor_vao, helicopter.main_rotor.index_count);
-        let tail_rotor_node = SceneNode::from_vao(heli_tail_rotor_vao, helicopter.tail_rotor.index_count);
+        let mut tail_rotor_node = SceneNode::from_vao(heli_tail_rotor_vao, helicopter.tail_rotor.index_count);
+        // Set reference point for tail rotor (pivot around its hub)
+        let mut tail_rotor_pin = tail_rotor_node.as_mut();
+        unsafe { tail_rotor_pin.get_unchecked_mut().reference_point = glm::vec3(0.35, 2.3, 10.4); }
 
         heli_root.add_child(&*body_node);
         heli_root.add_child(&*door_node);