I've finally found the time to tackle an issue that has been on the ToDo list for a while - render the glow of the heat shield during entry properly.
This has been a bit more tricky than I anticipated, but I am fairly happy with the final solution.
* max. temperature at the nose/leading wing edge is computed by the heating simulation
* using a temperature map based on the IR image the Kuiper Airborne Observatorium has taken of Columbia's heat shield during an entry, the max. temperature is mapped into a temperature field across the orbiter surface (I know this isn't 100% correct since the flow pattern and hence the location of hotspots has likely Mach dependence, so the image doesn't tell the whole story, but... we all have to finish somewhere, right?)
* and using some GLSL magic, the temperature value is converted into an (rgb) and mix factor corresponding to blackbody radiation at that temperature
Some bare tests of the heat map just inserting peak temperature by hand (temperatures are 750 K, 1000 K and 2000 K):
And in-situ testing during a simulated entry:
(The code can also do quite goofy things, like have the whole Shuttle glow in bright blue at 12.000 K temperature...)