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  Rotate an image with AffineTransform without coordinate change.  (Read 2024 times)
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Offline .

Junior Newbie





« Posted 2012-10-04 13:31:01 »



I have a game that i am making, where a ship is in the centre of the screen and planets scroll around it. The ship can rotate about it's centre, but can not change position.(the planets do that, for a scrolling effect) The problem is that I don't know how to move the planets in a certain direction based on where the ship is pointing. my first approach was to increment the planet's x and y coordinates based on where the ship was. example:
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if(ships_rotation > 22.5 && ships rotation < 67.5){
            planet.x-= ship.y*speed;
            planet.y+= ship.y*speed;
            }
However this is very time-consuming because I have to write similar code for every direction the planet moves, as well as having very choppy movement. So I decided to attach a AffineTransform to the planet, because as i have found out earlier, AffineTransform can rotate coordinates. This next block of code shows an example of moving the ship diagonally just by incrementing x.
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        aft.rotate(Math.toRadians(45));
        aft.translate(50,0);
However, there is one thing wrong with this code, and it is that the image rotates WITH the coordinates. My new approach is to rotate the image opposite the way I want it to go WITHOUT coordinate change, then rotate it back normally.(So the coordinates change) How can I accomplish this? I am open to other solutions, but NOT installing libraries. Thanks in advance.
Offline ReBirth
« Reply #1 - Posted 2012-10-04 15:04:01 »

Set/translate to the center of the image.

Offline Roquen
« Reply #2 - Posted 2012-10-04 16:58:57 »

I'm not really understanding your description.  The ship can rotate, but is always "shown" at the center of the screen.  The ship moves, it's just the "camera" is always keeping it in the center (so planets don't move when the ship does).
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Offline .

Junior Newbie





« Reply #3 - Posted 2012-10-04 21:51:03 »

I'm not really understanding your description.  The ship can rotate, but is always "shown" at the center of the screen.  The ship moves, it's just the "camera" is always keeping it in the center (so planets don't move when the ship does).
The ship turns, but stays in the center. The planets go past the ship to create a "moving" effect.
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