Add preliminary support for writing shape keys into MDL files

This is not complete as it only deals with the header data and doesn't
append the morphed vertices properly yet.

src/model.rs

@@ -368,6 +368,13 @@ impl Default for Vertex {
     }
 }
 
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct NewShapeValue {
+    pub base_index: u32,
+    pub replacing_vertex: Vertex
+}
+
 #[derive(Clone, Copy)]
 #[repr(C)]
 pub struct SubMesh {
@@ -633,7 +640,7 @@ impl MDL {
                         for shape_value in shape_values {
                             let old_vertex = vertices[indices[shape_value.base_indices_index as usize] as usize];
                             let new_vertex = vertices[shape_value.replacing_vertex_index as usize - model.meshes[j as usize].start_index as usize];
-                            let mut vertex = &mut morphed_vertices[indices[shape_value.base_indices_index as usize] as usize];
+                            let vertex = &mut morphed_vertices[indices[shape_value.base_indices_index as usize] as usize];
 
                             vertex.position[0] = new_vertex.position[0] - old_vertex.position[0];
                             vertex.position[1] = new_vertex.position[1] - old_vertex.position[1];
@@ -692,6 +699,48 @@ impl MDL {
         self.update_headers();
     }
 
+    pub fn remove_shape_meshes(&mut self) {
+        self.model_data.shape_meshes.clear();
+        self.model_data.shape_values.clear();
+
+        for lod in 0..3 {
+            for shape in &mut self.model_data.shapes {
+                shape.shape_mesh_count[lod] = 0;
+                shape.shape_mesh_start_index[lod] = 0;
+            }
+        }
+
+        self.update_headers();
+    }
+
+    pub fn add_shape_mesh(&mut self, lod_index: usize, shape_index: usize, shape_mesh_index: usize, part_index: usize, shape_values: &[NewShapeValue]) {
+        let part = &mut self.lods[lod_index].parts[part_index];
+
+        // TODO: this is assuming they are added in order
+        if shape_mesh_index == 0 {
+            self.model_data.shapes[shape_index].shape_mesh_start_index[lod_index] = self.model_data.shape_meshes.len() as u16;
+        }
+
+        self.model_data.shape_meshes.push(ShapeMesh {
+            mesh_index_offset: self.model_data.meshes[part.mesh_index as usize].start_index,
+            shape_value_count: shape_values.len() as u32,
+            shape_value_offset: self.model_data.shape_values.len() as u32
+        });
+
+        for shape_value in shape_values {
+            part.vertices.push(shape_value.replacing_vertex);
+
+            self.model_data.shape_values.push(ShapeValue {
+                base_indices_index: self.model_data.meshes[part.mesh_index as usize].start_index as u16 + shape_value.base_index as u16,
+                replacing_vertex_index: self.model_data.meshes[part.mesh_index as usize].start_index as u16 + (part.vertices.len() - 1) as u16
+            })
+        }
+
+        self.model_data.shapes[shape_index].shape_mesh_count[lod_index] += 1;
+
+        self.update_headers();
+    }
+
     pub(crate) fn update_headers(&mut self) {
         // update values
         for i in 0..self.file_header.lod_count {
@@ -784,6 +833,10 @@ impl MDL {
         for i in 0..self.lods.len() {
             self.file_header.index_offsets[i] = self.model_data.lods[i].index_data_offset;
         }
+
+        self.model_data.header.shape_count = self.model_data.shapes.len() as u16;
+        self.model_data.header.shape_mesh_count = self.model_data.shape_meshes.len() as u16;
+        self.model_data.header.shape_value_count = self.model_data.shape_values.len() as u16;
     }
 
     pub fn write_to_buffer(&self) -> Option<ByteBuffer> {