update README.md and Dockerfile

Dockerfile

@@ -13,10 +13,6 @@ RUN wget https://github.com/andrewwutw/build-djgpp/releases/download/v3.0/djgpp-
   tar xjf djgpp-linux64-gcc930.tar.bz2 && \
   rm djgpp-linux64-gcc930.tar.bz2
 
-RUN wget http://bisqwit.iki.fi/jutut/kuvat/programming_examples/djgpp_mesa.zip && \
-  echo 'e752ac3e63f24dc3d8048adf6ccde30f0abc13ae5469f528629b66eb5bdf63a4  djgpp_mesa.zip' | sha256sum djgpp_mesa.zip && \
-  unzip -p djgpp_mesa.zip libOSMesa.a > /lib/libOSMesa.a
-
 RUN mkdir /sm64
 WORKDIR /sm64
 ENV PATH="/sm64/tools:/djgpp/bin:${PATH}"

README.md

@@ -24,6 +24,20 @@ For *best* performance:
  - Use `ENABLE_OPENGL_LEGACY=1` to enable the legacy OpenGL renderer
  - Use `DISABLE_SKYBOX=1` to avoid drawing the skybox
  - Use `DISABLE_AUDIO=1` to save your ears and some CPU cycles
+ - Use `DOS_GL=dmesa` to enable 3Dfx-backed OpenGL instead of software-backed (this only works with legacy OpenGL!)
+
+### 3Dfx mode:
+
+When `DOS_GL` is set to `dmesa`, the game will render using FXMesa, which is a Mesa driver that uses 3Dfx for rendering.
+That means you will need a 3Dfx card (Voodoo II and above recommended, but will run on a Voodoo I probably) and appropriate
+drivers to run it.
+
+The drivers can be obtained from this repository (see [lib/glide3/README.md](lib/glide3/README.md)). Put the appropriate
+`glide3x.dxe` file next to the EXE.
+
+When running Windows 9x, you will have to reboot into DOS mode before running the game for this to work.
+
+dosbox-x and PCem can emulate Voodoo cards for testing purposes.
 
 ## Running