C++ – How to convert quadratic bezier curve code into cubic bezier curve

bezierccurvedirectxopengl

So I've recently picked up graphics programming and I wanted to compute a cubic Bézier curve. I found this excellent answer on quadratic Bézier but I don't know how to convert this to a cubic Bézier curve.

Best Answer

For cubic Bézier curve, as you see in the link you shared, the green lines are obtained from the same procedure as the quadratic one. the differences are: you have two green lines, and then you need to calculate a blue line based on them. So the for loop changes as: 

for( float i = 0 ; i < 1 ; i += 0.01 )
{
    // The Green Lines
    xa = getPt( x1 , x2 , i );
    ya = getPt( y1 , y2 , i );
    xb = getPt( x2 , x3 , i );
    yb = getPt( y2 , y3 , i );
    xc = getPt( x3 , x4 , i );
    yc = getPt( y3 , y4 , i );

    // The Blue Line
    xm = getPt( xa , xb , i );
    ym = getPt( ya , yb , i );
    xn = getPt( xb , xc , i );
    yn = getPt( yb , yc , i );

    // The Black Dot
    x = getPt( xm , xn , i );
    y = getPt( ym , yn , i );

    drawPixel( x , y , COLOR_RED );
}
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