WebGLRenderer: Add initial support for multi draw BatchedMesh (#666)

Author: Methuselah96

types/three/examples/jsm/objects/BatchedMesh.d.ts

@@ -21,6 +21,9 @@ declare class BatchedMesh extends Mesh<BufferGeometry, Material> {
 
     _geometryInitialized: boolean;
     _geometryCount: number;
+    _multiDrawCounts: Int32Array | null;
+    _multiDrawStarts: Int32Array | null;
+    _multiDrawCount: number;
 
     _matrices: Matrix4[];
     _matricesTexture: DataTexture | null;

types/three/src/renderers/webgl/WebGLBufferRenderer.d.ts

@@ -11,7 +11,8 @@ export class WebGLBufferRenderer {
         capabilities: WebGLCapabilities,
     );
 
-    setMode(value: any): void;
-    render(start: any, count: number): void;
-    renderInstances(start: any, count: number, primcount: number): void;
+    setMode: (value: any) => void;
+    render: (start: any, count: number) => void;
+    renderInstances: (start: any, count: number, primcount: number) => void;
+    renderMultiDraw: (starts: Int32Array, counts: Int32Array, drawCount: number) => void;
 }

types/three/src/renderers/webgl/WebGLIndexedBufferRenderer.d.ts

@@ -1,8 +1,9 @@
 export class WebGLIndexedBufferRenderer {
     constructor(gl: WebGLRenderingContext, extensions: any, info: any, capabilities: any);
 
-    setMode(value: any): void;
-    setIndex(index: any): void;
-    render(start: any, count: number): void;
-    renderInstances(start: any, count: number, primcount: number): void;
+    setMode: (value: any) => void;
+    setIndex: (index: any) => void;
+    render: (start: any, count: number) => void;
+    renderInstances: (start: any, count: number, primcount: number) => void;
+    renderMultiDraw: (starts: Int32Array, counts: Int32Array, drawCount: number) => void;
 }