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processing4/java/examples/Books/Nature of Code/chp5_physicslibraries/CollisionsEqualMass/drawVector.pde

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void drawVector(PVector v, PVector loc, float scayl) {
pushMatrix();
float arrowsize = 4;
// Translate to location to render vector
translate(loc.x,loc.y);
stroke(0);
// Call vector heading function to get direction (note that pointing up is a heading of 0) and rotate
rotate(v.heading2D());
// Calculate length of vector & scale it to be bigger or smaller if necessary
float len = v.mag()*scayl;
// Draw three lines to make an arrow (draw pointing up since we've rotate to the proper direction)
line(0,0,len,0);
line(len,0,len-arrowsize,+arrowsize/2);
line(len,0,len-arrowsize,-arrowsize/2);
popMatrix();
}
void mousePressed() {
showVectors = !showVectors;
}