max lacks a curve drawing tool with an intuitive GUI?!?

On Sep 8, 2007, at 10:03 AM, Johannes wrote:

> I don't know, if it's better for understanding now, but maybe
> somebody has an idea, how to put "endless" many points into the
> bspline-object...

hello, i did put endless points in a spline object...
splining is just a fancy interpolation that instead of using 2 normal
points as end, begin, it usually uses 4, drawing only in the space
between the middle two control points.

so basically, you need to keep track where you are interpolating, and
the moment you reach the end of _this 4 points interp_ you should
instantly change the control points, in fifo fashion. this behaviour
will make your spline continuous.

some pseudo code that exhibits continuous point calling spline and
regular spline reading n breakpoints..

// inside the object define:

//4 points for the continuous spline interp+next point
pt pt1,pt2,pt3,pt4,next;

// N breakpoints for regular spline path making
pt points[];
int numbreakpoints;

// store a head val that will keep track of where you are in the spline
float head=0.;
float stride=0.01;

// an example continuous function will only be triggered when
// you reach past 1. in the head

void spline_continuous_setpoint(pt next) {
    //fifo control points
    pt1 = pt2;
    pt2 = pt3;
    pt3 = pt4;
    pt4 = next;
}

pt read_spline_continuous() {

    //advance control val
    head+=stride;
    if(head>1.) {
        head-=1.; //make sure control wraps
        notify_user_point_is_past_head_so_he_can_update_next_pt();

        pt nextpt = read_next_pt_into_x->next();
        spline_continuous_setpoint(nextpt);
    }

    pt =    somespline(p1,p2,p3,p4,head);

    return pt;
}

pt read_spline_control_points() {

    //advance control val and find control points
    head+=stride;
    if(head>x->numbreakpoints-2)
        head-=x->numbreakpoints-2; //make sure control acesses all stored
points

    int c = (int) head; //cheap floor
    float sinterp = head-c; //set the spline interp range 0.-1. in
between breakpoints

    // so the points for the spline interp are..

    p1 = x->points[c-1];
    p2 = x->points[c+0];
    p3 = x->points[c+1];
    p4 = x->points[c+2];

    // perform the spline function with 4 points above and current head
value

    pt = somespline(p1,p2,p3,p4,sinterp);

    return pt;
}

if you want to see some code working, check out a-hspline3d from my
a-objects, available in my site at www.s373.net/code

the 'stack' message i implemented in the object uses these coding
concepts
to make a continuous ever-ending spline. however, its not an object
suitable
for curve drawing in max, i guess..

hope this helps,

a