Question

I am having trouble finding out how to form a triangle (not sawtooth) wave from a sine wave.

I understand how to create it for a Square wave:

if( sineValue >= 0 )
        value = amp;
    else
        value = -amp;

But I am not sure how to change this to accommodate for a triangle wave.

Answer 1

A triangle wave is the integral of a square wave. So you need to integrate (sum) your square wave over time:

if (sineValue >= 0)
{
    value += delta;
}
else
{
    value -= delta;
}

Note that this can be written more succinctly as:

value += (sineValue >= 0) ? delta : -delta;