WPF has Presentation Framework, Presentation Core & Composition Engine (MIL).

Each one sit on the top of the other in the following order

1. Composition Engine

2. Presentation Core &

3. Presentation Framework

WPF uses 3D pipeline to render everything.  It uses 3d hardware and graphics card while rendering, even to render 2D graphics.

1. Composition Engine Is also called MIL, Media Integration Layer. It takes Bitmaps, Vectors, and media render them to the DirectX. MIL sits as unmanaged layer to minimize CPU usage

2. Presentation Core

It provides .NET API that uses rendering services for the MIL. During graphics programming we work with Core API.

3. Presentation Framework

Most of the important WPF elements are in Presentation Framework. Provides high-level services like layout, data binding, command handling.