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  [Solved] LibGdx - Wierd behavior with Sprite rotation  (Read 2104 times)
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Offline mrbenebob

Junior Newbie

« Posted 2013-06-19 13:09:54 »

So I was going to have a go at making a little 2D space action combat game, but have unfortunately fallen at the first hurdle and cant seem to get the players ship going in the right direction.

The ship has an X and Y, an X Velocity value, a Y Velocity and an angle, all floats.

When the up key is pressed, a force is added to the X and Y velocities depending on the ships rotation.

            shipVX += 0.05 * (float) Math.cos(shipAngle);
            shipVY += 0.05 * (float) Math.sin(shipAngle);

However, the ships angle and the directions of the force don't seem to match up in any way. I've tried rejigging that bit of code, but cant get anything that makes any sense.  Undecided

Its probably just my maths that's at fault, haven't had to do any physics since college, anyway, any thoughts and suggestions would be greatly appreciated.

Full code here:
Offline heisenbergman

JGO Coder

Medals: 14

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« Reply #1 - Posted 2013-06-19 13:59:57 »

^ Is your shipAngle variable in degrees? Because if it is, you need to convert it to radians:

            shipVX += 0.05 * (float) Math.cos(Math.toRadians(shipAngle));
            shipVY += 0.05 * (float) Math.sin(Math.toRadians(shipAngle));

Offline davedes
« Reply #2 - Posted 2013-06-19 14:08:19 »

Some useful LibGDX utilities worth noting:
MathUtils.cosDeg( angleInDegrees )
MathUtils.sinDeg( angleInDegrees )

MathUtils.cos( angleInRadians )
MathUtils.sin( angleInRadians )

MathUtils.PI2  //PI * 2, already cast to float
MathUtils.PI    //already cast to float

float rad = degrees * MathUtils.degRad //degrees to radians
float deg = radians * MathUtils.radDeg  //radians to degrees

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Offline mrbenebob

Junior Newbie

« Reply #3 - Posted 2013-06-19 14:44:21 »

Ah, that'll be it, knew I was missing something dumb.
Thanks guys, working now  Grin
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