Overview
MIDAS is a client/server application that allows you to deliver the graphics power of a remote display to your local workstation.
It works by redirecting the OpenGL of an unmodified application to a different display, then sending the imagery back into the window of the original application. In this way, the hardware-accelerated OpenGL features of a graphics card may be used on a completely separate display. It decouples the OpenGL implementation from the final display.
MIDAS demo
Concept
In the X Window System, OpenGL is delivered to the end user through the GLX protocol. This protocol embeds OpenGL commands inside the X11 stream. All OpenGL primitives generated by the application are delivered over the network to the end user's desktop for rasterization and display.
While this provides much needed network transparency for remote applications, it is not very flexible when it comes to the hardware doing the rasterization. Only the user's desktop machine can be used to accelerate the display.
OpenGL
MIDAS (Merlot Image Delivery Application Server) augments the services that X11 and GLX provide by redirecting the GLX commands to a second "high end" machine. Primitives are rendered there, and imagery is shipped back to the user's desktop for display. Since the imagery is blitted back into the original application's window, the user has the same experience with the application as they are used to.
One major advantage of this is that the second machine can be a much higher-end machine than is feasible to put on a user's desktop. Plus, it can be a shared resource. When one user is not using it, others can. This makes for a very flexible and cost effective remote delivery solution.
MIDAS (Merlot Image Delivery Application Server)
Another advantage is that all rendering is done in "direct" mode. Most OpenGL applications will see dramatic speedups when rendering is done on a local GLX/X11 display. Thus, while MIDAS adds additional overhead due to its processing, this overhead may be more than made up by the speedups of using direct rendering.

MIDAS may also be used in a second, more advanced mode, where the application is run on a different machine than the one doing the rendering or the final display. This method has the advantage of a complete decoupling of the application, the rendering, and the final display. However, it removes the advantage of direct rendering. MIDAS may also be used in a second, more advanced mode
Notable Technology and Merlot
To insert itself into an unmodified OpenGL application, MIDAS makes use of the system's runtime loader. The midas_launch script sets up environment variables that cause the system to load MIDAS's library before the system's OpenGL library is loaded. MIDAS's library contains implementations of certain OpenGL functions (glXSwapBuffers, glXMakeCurrent, etc.) that allow the GLX stream to be redirected. This is similar to how systems like Chromium work.

MIDAS makes use of compression and temporal coherence to reduce the payload that is transmitted over the network. For each window, the frame is compared to the frame immediately preceding it, and a delta is calculated. Only this delta is considered for transmission.
MIDAS example - MIDAS Example = MIDAS example
After a delta is computed, the image is then compressed. MIDAS currently supports two different forms of compression: RLE (Run-Length Encoding) and gzip compression. RLE compression (the default) provides the least compression, but requires the least computation to encode and decode. Gzip compression at level 6 requires a good amount of computation, and so is most appropriate in low bandwidth situations, especially coupled with frame differencing.

Currently, MIDAS's compressors are hardcoded. Only temporal differencing, RLE, and gzip are supported. Once Merlot is sufficiently developed, MIDAS will be adapted to use its more flexible image transport mechanisms.
Current Status and Download
MIDAS is currently under active development. The current 0.8.8 version is very usable, and has been demonstrated to work well in a number of environments.
MIDAS 0.8.8 source code
Change history:
  • Version 0.8.8:
    • Made midas_launch stop looking for the binary, and instead just watch if execvp executes properly.
    • Compatibility fixes for Windows.
  • Version 0.8.7:
    • Added much more thread safety.
    • Added a -port option to midas_receiver, allowing the specification of the listening port. Without this, the port is randomly chosen between 1024 and 49151.
Contact
For more information about MIDAS, contact Sean Ahern.
For more information about ASC visualization, contact Rebecca Springmeyer