Thank you! Thank you thank you thank you....

hey, I just rewrote this last night with support for prismatic joints, and in a more object oriented way, so it can be easily extended to add more segments.

the prismatics don't work too great at any position besides the base of the arm, unfortunately...



int sx,sy,ex,ey,hx,hy,hxo,hyo;
int armLength,ua,la;
float uad, lad;
ArrayList segments;
int numSegments = 4;

void setup(){
size(500,500);
segments = new ArrayList();
background(255, 224, 150);
for(int i=0;i<numSegments;i++){
Segment segment = new Segment(83.4, 10);
segments.add(segment);
}
Segment current = (Segment)segments.get(3);
current.x = 0;
current.y = 250;
current.type = 1;
current = (Segment)segments.get(1);
//current.type = 1;
}
void draw(){
background(255, 224, 150);
PVector target = reach((Segment)segments.get(0), mouseX, mouseY);
for(int i=1;i<segments.size();i++){
target = reach((Segment)segments.get(i), target.x, target.y);
}
for(int i=segments.size()-1;i>0;i--){
position((Segment)segments.get(i-1), (Segment)segments.get(i));
}
for(int i=0;i<segments.size();i++){
Segment current = (Segment)segments.get(i);
current.draw();
}
}
PVector reach(Segment segment, float xpos, float ypos)
{
float dx = xpos - segment.x;
float dy = ypos - segment.y;
if(segment.type == 0){
float angle = atan2(dy, dx);
segment.rotation = angle;
//segment.rotation += (angle-segment.rotation)*0.3;
}
else{
float h = sqrt(pow(dx, 2)+pow(dy, 2));
//println(segment.rotation);
float pinRot = atan2(segment.getPin().y-segment.y, segment.getPin().x-segment.x);
float missingAngle = PI-(segment.rotation-pinRot+(PI/2));
/*
println("pin rotation: "+degrees(pinRot));
println("segment rotation: "+degrees(segment.rotation));
println("missing angle: "+degrees(missingAngle));
*/
//float a = h*sin(missingAngle);
//segment.segmentWidth = sqrt(pow(h, 2)+pow(a, 2)-2*h*a*cos(missingAngle));

segment.segmentWidth += (h*sin(missingAngle)-segment.segmentWidth)*0.3;
}
float w = segment.getPin().x - segment.x;
float h = segment.getPin().y - segment.y;
float tx = xpos - w;
float ty = ypos - h;
return new PVector(tx, ty);
}
void position(Segment segmentA, Segment segmentB)
{
//if(segmentA.type == 0){
segmentA.x = segmentB.getPin().x;
segmentA.y = segmentB.getPin().y;
//}

//else{
if(segmentA.type == 1){
segmentA.rotation = segmentB.rotation;
}
}

class Segment{
float segmentWidth, segmentHeight, vx, vy, rotation, x, y;
int type;
Segment(float _segmentWidth, float _segmentHeight){
segmentWidth = _segmentWidth;
segmentHeight = _segmentHeight;
type = 0;
}
PVector getPin()
{
float xPos = x + cos(rotation) * segmentWidth;
float yPos = y + sin(rotation) * segmentWidth;
return new PVector(xPos, yPos);
}
void draw(){
color(255, 255, 255);
ellipseMode(CENTER);
//rotate(rotation, 0, 0, 1);
ellipse(x, y, 10, 10);
ellipse(x+cos(rotation)*segmentWidth, y+sin(rotation)*segmentWidth, 10, 10);
line(x, y, x+cos(rotation)*segmentWidth, y+sin(rotation)*segmentWidth);
}
}

thank you for sharing!

i've also been trying to expand the code to incorporate more segments and varying segment lengths but to no avail. did you eventually succeed Jonathan?

cheers