garageCube

I am using a MacBook Pro (Retina, 15-inch, Mid 2015) with OS 10.10.5 to run Madmapper. I am projecting to 4 projectors. 3 using a Matrox TripleHead2Go DP Edition and 1 to HDMI. My MacBook seems to be able to handle the processing but you can hear the fans running and it gets hot. I need the projection to run for 2 hours.

Can anyone suggest how to get my laptop to run not as hot?

4 outputs that's a lot for your graphic card.... so it will naturally heat.
However that shouldn't be problem, I've let mine overheat for hours .. it didn't melt.

Letting some air flow underneath the bottom can be a good idea, but personally, usually I don't care.
Eventually you could get a laptop cooler pad such as:
https://www.google.fr/?client=safari#q= ... cooler+pad

but you'll have to sacrifice on the style....

hey stephan, as Franz said that´s totally normal.

A Macbook can reach around 90° Celsius under load without getting any problems or lagging, and because of it´s aluminum housing the most of the heat comes to the outside and you might think it´s too hot, but it is fine ^^

you can use software like smcfancontrol to monitor the temperature and fans. https://github.com/hholtmann/smcFanControl/releases

if you still want to take care, just take a look at laptop cooling pads like these:
https://www.google.de/search?q=laptop+cooler&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiEs_nNu_7LAhUJXiwKHR-4CpoQ_AUICCgC&biw=1366&bih=653