Bezier curve
in
Programming Questions
•
8 months ago
Hi, found this sketch on openprocessing.
I want to use this in some project and wanted to ask, how can i change the
speed of the ellipse going from point A to B in the following code.
The cubic equations (xn and yn) are from wiki.[bezierPoint() wasn't exactly helping] Search 'Bezier curves' on wiki. Anyway, Here's the code-
- float x1, y1, x2, y2, x3, y3, x4, y4, t;
- void setup() {
- size(200,200);
- t = 0;
- x1 = 10;
- y1 = 180;
- x2 = 50;
- y2 = 5;
- x3 = 100;
- y3 = 10;
- x4 = 180;
- y4 = 180;
- noFill();
- }
- void draw() {
- background(255.0);
- stroke(0.0);
- strokeWeight(1.0);
- beginShape();
- vertex(x1, y1);
- bezierVertex(x2, y2, x3, y3, x4, y4);
- endShape();
- //find any point on the curve:
- t+=0.01;
- if(t>1) { t=0; }
- double mu, mum1,mum13,mu3;
- mu = t;
- mum1 = 1 - mu;
- mum13 = mum1 * mum1 * mum1;
- mu3 = mu * mu * mu;
- float xn = (float) ( mum13*x1 + 3*mu*mum1*mum1*x2 + 3*mu*mu*mum1*x3 + mu3*x4 );
- float yn = (float) ( mum13*y1 + 3*mu*mum1*mum1*y2 + 3*mu*mu*mum1*y3 + mu3*y4 );
- stroke(255.0, 0.0, 0.0);
- strokeWeight(5.0);
- point(xn, yn);
- stroke(0.0, 100.0);
- strokeWeight(1.0);
- line(x1, y1, x2, y2);
- line(x2, y2, x3, y3);
- line(x3, y3, x4, y4);
- //intersecion
- float x12 = x1+(x2-x1)*t;
- float y12 = y1+(y2-y1)*t;
- float x23 = x2+(x3-x2)*t;
- float y23 = y2+(y3-y2)*t;
- float x34 = x3+(x4-x3)*t;
- float y34 = y3+(y4-y3)*t;
- line(x12, y12, x23, y23);
- line(x23, y23, x34, y34);
- float x123 = x12+(x23-x12)*t;
- float y123 = y12+(y23-y12)*t;
- float x234 = x23+(x34-x23)*t;
- float y234 = y23+(y34-y23)*t;
- line(x123, y123, x234, y234);
- stroke(255.0, 0.0, 0.0);
- strokeWeight(2.0);
- point(x123,y123);
- point(x234,y234);
- stroke(255.0, 0.0, 0.0, 100.0);
- strokeWeight(3.0);
- beginShape();
- vertex(x1, y1);
- bezierVertex(x12, y12, x123, y123, xn, yn);
- endShape();
- stroke(0.0, 255.0, 0.0, 100.0);
- beginShape();
- vertex(x4, y4);
- bezierVertex(x34, y34, x234, y234, xn, yn);
- endShape();
- }
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