Lookup Table of 12bits in VHDL

I assume the LUT is for a sine wave, where the amplitude is quantized to 12 bits. How many look up points do you need? If it isn't many you can build the full sine wave (1 period) in a lut array: http://stackoverflow.com/questions/21976749/design-of-a-vhdl-lut-module

If you want more resolution, you can create half period lut arrays (t = [0: pi]) or quarter period (t = [0:pi/2]) lut arrays. But then you would need more logic to infer values outside of the lut array range.