wip: begin refactor of model loading system

src/gpu/material.rs

@@ -0,0 +1,9 @@
+use vulkano::buffer::BufferContents;
+
+/// Mirrors the `MaterialPushConstants` block in `triangle_frag.glsl`. Pushed once per submesh
+/// draw call, since each submesh may use a different material.
+#[derive(BufferContents, Debug, Clone, Copy)]
+#[repr(C)]
+pub struct MaterialPushConstants {
+    pub base_color: [f32; 4],
+}