Continue rotating a circular image with mouseDragged where it was left off

Processing Coding Questions
1

Hi, I’m trying to rotate a circular image on mouseDragged and I got the image to rotate when dragging the mouse but when I stop dragging and start dragging again from a different position of the image it doesn’t continue the drag where it was left off. How can I start dragging again from its end position. This is some of the code I have:

float rotAngle = 0;
void draw(){ 
    pushMatrix();
    translate(width/2, height/2);
    rotate(rotAngle);
    imageMode(CENTER);
    image(abc, 0, 0, ABC_SIZE, ABC_SIZE);  //abc is the image and ABC_SIZE the size of the image
    popMatrix();  
}

void mouseDragged(){
    rotAngle = atan2(mouseY - height/2, mouseX - width/2);
}
1 Like
2

I was able to kinda do it with this code:

float rotAngle, originalRotAng, newRot, originalTouchAng = 0;
void draw() { 
    if (mousePressed == true) {
       originalTouchAng = atan2(mouseY - height/2, mouseX - width/2);   //original angle at which the image was tapped
    }
    pushMatrix();
    translate(width/2, height/2);
    rotate(rotAngle);
    imageMode(CENTER);
    image(abc, 0, 0, ABC_SIZE, ABC_SIZE);  //abc is the image and ABC_SIZE the size of the image
    popMatrix();  
}

void mouseDragged() {
    originalRotAng = rotAngle;                              // original angle of the image
    newRot = atan2(mouseY - height/2, mouseX - width/2);    // 
    rotAngle = originalRotAng + newRot - originalTouchAng;  // new angle for the rotation of the image
}

It does continue the rotation where it was left off but now it rotates way faster than the mouse drag the farther it is rotated from the center. Any ideas?

3

If you want it to “smoothly” rotate, maybe base the newRot off of the change of the mouse’s position (Something like mousex - pmousex).

Otherwise, just try different things! There’s no right way to do this haha

Edit: Welcome to the forums!

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4

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