Weird Plasma

[Zaei]

I am having a strange problem. I am using a plasma function in VB, and it works great, but it is mush to slow. So, I tried to convert it into C++, but the function seems to be returning incorrect values. I have attached an image of just how odd it looks. The function is this:

32 + 63 * fabs(sin(hypot(400 - j, 400 - i) / 72) + cos(0.5 * 13 * sin(i / 65) + sin(j / 50)));

Any help is appreciated.

Z.