feat: actors stage 1

engine/render/Material.ts

@@ -0,0 +1,12 @@
+import type { Texture } from "./Texture"
+import type { Mesh } from "../scene/Mesh"
+
+/** How a surface is drawn: which texture, and whether back-faces are culled.
+ *  (Alpha-cutout is global in the `Rasterizer`.) A `Material` is shared by every
+ *  draw that uses it, so the renderer no longer needs to know content by name. */
+export type Material = { texture: Texture; cull: boolean }
+
+/** A baked mesh paired with the material it draws with. A chunk (or any baked
+ *  batch) is just a list of these, so adding a new surface/texture is data, not a
+ *  new branch in the render loop. */
+export type DrawGroup = { mesh: Mesh; material: Material }