Custom Tool.

Move the cursor across the screen to draw. In addition to creating software tools to simulate pens and pencils, it is possible to create unique tools to draw with.

int dots = 1000;
float[] dX = new float[dots];
float[] dY = new float[dots];

float l_0 = 0.0;
float h_0 = 0.0;

float legX = 0.0;
float legY = 0.0;
float thighX = 0.0;
float thighY = 0.0;

float l = 60.0; // Length of the 'leg'
float h = 90.0; // Height of the 'leg'

float nmx, nmy = 0.0;
float mx, my = 0.0;

int currentValue = 0;
int valdir = 1;

void setup() 
{
  size(640, 360);
  noStroke();
  smooth();
  background(102);
}

void draw() 
{
  // Smooth the mouse
  nmx = mouseX;
  nmy = mouseY;
  if((abs(mx - nmx) > 1.0) || (abs(my - nmy) > 1.0)) { 
    mx = mx - (mx-nmx)/20.0;
    my = my - (my-nmy)/20.0;

    // Set the drawing value
    currentValue += 1* valdir;
    if(currentValue > 255 || currentValue <= 0) {
      valdir *= -1;
    }
  }

  iKinematics();
  kinematics();

  pushMatrix();
  translate(width/2, height/2);
  stroke(currentValue); 
  line(thighX, thighY, legX, legY);
  popMatrix();

  stroke(255);
  point(legX + width/2, legY + height/2);
}

void kinematics() 
{
  thighX = h*cos(h_0);
  thighY = h*sin(h_0);
  legX = thighX + l*cos(h_0 - l_0);
  legY = thighY + l*sin(h_0 - l_0);
}

void iKinematics()
{
  float tx = mx - width/2.0;
  float ty = my - height/2.0;
  float c2 = (tx*tx + ty*ty - h*h - l*l)/(2*h*l); //in degrees
  float s2 = sqrt(abs(1 - c2*c2)); // the sign here determines the bend in the joint  
  l_0 = -atan2(s2, c2);
  h_0 = atan2(ty, tx) - atan2(l*s2, h+l*c2);
}