If you're affiliated with a university, it's very likely that a Matlab license is already available to you. I do research in graphics, and I find it extremely productive to test ideas in Matlab. you can hardly find a better time-saving procedure than testing an idea in Matlab and knowing in 10 minutes that it doesn't work, instead of spending a week implementing it in C++. Once you find what works, re-implementation in C++ is a breeze.