Is there a faster sine function?

Question

I am working on generation 3d perlin noise. The C# Math library seems like overkill for what I need since most of its functions use double percision. I use Math.Sin() in several places to generate the noise. Does anyone know of a faster sine function?

Answer 1

You can use a parabola to aproximate the value of the sine function. This has the advantage of having the roots at exactly -pi/2 and pi/2 which is usually not the case with other fast approximations based on the TaylorSeries or MaclaurinSeries.

public float Sin(float x)
{
    const float B = 4 / PI;
    const float C = -4 / (PI*PI);

    return -(B * x + C * x * ((x < 0) ? -x : x));
} 

Here is a comparison to the actual sine function:

Answer 2

What is the range of input values to your sin() function? For what you're using it for, it sounds like they might be limited, which means you could pre-compute the values. For instance, if you're rounding up the input values to the nearest degree, then you only have 360 possible values - just pre-compute them and store in a table.

If you need slightly more values, say to one decimal place, you could interpolate from the table - I'm not familiar with perlin noise, but the word "noise" seems to indicate it doesn't require high accuracy. :) (You could also just make a larger table, 3600 entries isn't much space).

Answer 3

You might want to read this too, it's got fast sine and cosine approximations