update doc

docs/building.md

-[[Home]](index) [[Mesh Edit]](./meshedit/overview) [[Path Tracer]](./pathtracer/overview) [[Animation]](./animation/overview)
+[[Home]](/docs/index.md) [[Mesh Edit]](/docs/meshedit/overview.md) [[Path Tracer]](/docs/pathtracer/overview.md) [[Animation]](/docs/animation/overview.md)
 
 ---
 
@@ -6,7 +6,7 @@
 
 <!-- ![Ubuntu Build Status](https://github.com/CMU-Graphics/Scotty3D/workflows/Ubuntu/badge.svg) ![MacOS Build Status](https://github.com/CMU-Graphics/Scotty3D/workflows/MacOS/badge.svg) ![Windows Build Status](https://github.com/CMU-Graphics/Scotty3D/workflows/Windows/badge.svg) -->
 
-To get a copy of the codebase, see [Git Setup](./git).
+To get a copy of the codebase, see [Git Setup](/docs/git.md).
 
 Note: the first build on any platform will be very slow, as it must compile most dependencies. Subsequent builds will only need to re-compile your edited Scotty3D code.
 

docs/git.md

-[[Home]](index) [[Mesh Edit]](./meshedit/overview) [[Path Tracer]](./pathtracer/overview) [[Animation]](./animation/overview)
+[[Home]](/docs/index.md) [[Mesh Edit]](/docs/meshedit/overview.md) [[Path Tracer]](/docs/pathtracer/overview.md) [[Animation]](/docs/animation/overview.md)
 
 ---
 

docs/index.md

-[[Home]](/docs/index) [[Mesh Edit]](/docs/meshedit/overview) [[Path Tracer]](/docs/pathtracer/overview) [[Animation]](/docs/animation/overview)
+[[Home]](/docs/index.md) [[Mesh Edit]](/docs/meshedit/overview.md) [[Path Tracer]](/docs/pathtracer/overview.md) [[Animation]](/docs/animation/overview.md)
 
 ---
 
@@ -11,14 +11,14 @@ constitutes the majority of the coursework for CS403 (Computer Graphics) at Shan
 
 
 These pages describe how to set up and use Scotty3D. Start here!
-- [Git Setup](/docs/git): create a private git mirror that can pull changes from Scotty3D.
-- [Building Scotty3D](/docs/building): build and run Scotty3D on various platforms.
-- [User Guide](/docs/guide/guide): learn the intended functionality for end users.
+- [Git Setup](/docs/git.md): create a private git mirror that can pull changes from Scotty3D.
+- [Building Scotty3D](/docs/building.md): build and run Scotty3D on various platforms.
+- [User Guide](/docs/guide/guide.md): learn the intended functionality for end users.
 
 The developer manual describes what you must implement to complete Scotty3D. It is organized under the three main components of the software:
-- [MeshEdit](/docs/meshedit/overview)
-- [PathTracer](/docs/pathtracer/overview)
-- [Animation](/docs/animation/overview)
+- [MeshEdit](/docs/meshedit/overview.md)
+- [PathTracer](/docs/pathtracer/overview.md)
+- [Animation](/docs/animation/overview.md)
 
 ## Project Philosophy
 
@@ -28,7 +28,7 @@ Scotty3D, which is a modern package for 3D modeling, rendering, and animation.
 In terms of basic structure, this package doesn't look much different from
 "real" 3D tools like Maya, Blender, modo, or Houdini. Your overarching goal is
 to use the developer manual to implement a package that
-works as described in the [User Guide](/docs/guide/guide), much as you would at a real
+works as described in the [User Guide](/docs/guide/guide.md), much as you would at a real
 software company (more details below).
 
 Note that the User Guide is **not** an Assignment Writeup. The User Guide