Rotate object to point at mouse position

Question

I have an image of a spaceship, which I want to rotate to point at the mouse position. To calculate the angle I have to rotate I use the following code:

void CinderGaemApp::CalculateAngleBetweenMouseAndObject() { float deltaY = mouseLoc_.y - 10; //hardcoded y coordinate of the tip of the spaceship float deltaX = mouseLoc_.x - 0; //hardcoded x coordinate of the tip of the spaceship angleInDegrees_ = atan2(deltaY,deltaX) * 180 / 3.141; }

After that I update my player object:

void Player::update(float degree) { gl::pushMatrices(); gl::translate(20,20); gl::rotate(degree); gl::translate(-20,-20); gl::popMatrices(); }

Then I draw it. But my problem is, when I use gl::popMatrices(), the image isnt moving at all. If I remove gl::popMatrices(), the image first spins around for 2 seconds or so and is then not pointing correct to the mouse. Is there anything wrong with my code? Please comment if you need more code, I am not really sure how much information you need.

ratchet freak · Accepted Answer · 2013-12-12 09:54:14Z

you need to put the sequence in your render function:

void Player::render() { gl::pushMatrices(); gl::translate(position.x, position.y); gl::translate(20,20); gl::rotate(my_degree); gl::translate(-20,-20); // do other render operations gl::popMatrices(); }

with update simply being

void Player::update(float degree) { my_degree=degree; }

because each block between matching pushMatrix and popMatrix is independent so the code you had in your update was a noop

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