Develop Reference

Rotate item in a circle shape using phone accelerometer/gravity sensor vector

I'm trying to make a small circle move in another bigger circle as a ball moving in circle relative to Android phone tilting. I'm doing this in Godot but I think the principle is the same in all game engines probably. I make a scene in Godot and add two sprites as the two circles as the following picture. I get the accelerometer 3D vector, use x and y values and calculate the angle in x and y plate (relative to y axis i.e Vector2(0, 1) ) and rotate the mentioned scene to that degree using an animation, using this code
func _process(delta: float) -> void:
var vec3 = Input.get_accelerometer()
accelVec = Vector2(-stepify(vec3.x, 0.1), -stepify(vec3.y, 0.1))
var angle = accelVec.angle_to(Vector2(0, 1))
rotateTween.interpolate_property(self, "rotation", rotation, angle, 0.2,
Tween.TRANS_LINEAR)
rotateTween.start()
return
But the problem lies in here that when the x value of accelerometer 3D vector changes from a positive to negative value i.e when the ball is at top of the circle and is going to go to the other half of the circle, it actually moves from bottom of the circle to the desired point rather than from top of the circle.
I hope I explained the problem well, though I doubt it.
I added the Gif that shows actual test on an android phone here Testing in Android.
Any idea how to solve this problem?
Thanks in advance.

This is because Tween is interpolating linear values. It doesn't know it's working with angles, or that they should wrap around.
So when you're at -179 degrees and you tween to 179--a difference of 2 degrees--Tween just sees -179 -> 179 and goes through the whole circle.
You probably don't need a Tween here at all because _process() happens every frame.

TranslateAnimation not moving view to correct place

I have two ImageViews inside a constraint layout. One on top and one on bottom. I want to move the bottom one onto the top one. Of course I know it doesn't change it's actual position which I am ok with. When I use TranslateAnimation to move to the specified coordinates the image goes down and to the right instead of moving up and to the right. Also when it moves to the right it is slightly off. I can use view.animate().y(getTop).x(getLeft); and it moves the image into the correct position but then it is stuck there. I can't get it to move back to its original like it would if fillAfter was false.
First I get the destination location
float x = playerOneCard.getLeft();
float y = playerOneCard.getTop();
This code moves the card to the correct location but does not reset it after being moved. I need it to essentially move there, go back to it's original place, and repeat as many times as the button is pressed.
playerOneCardMove.animate().x(x).y(y);
This code moves the image but down and towards the right no where close to lining up with the desired destination.
TranslateAnimation translateAnimation = new
TranslateAnimation(Animation.ABSOLUTE,x,Animation.ABSOLUTE,y);
translateAnimation.setDuration(500);
translateAnimation.setFillAfter(false);
playerOneCardMove.startAnimation(translateAnimation);

Figured it out. Since I was going from the absolute position of the first image the top left of that image is 0,0. So it was moving accordingly. Instead I measured the distance from the top of the image on the bottom to the top of the image above it and then moved it according to distance. I did the same for both x and y coordinates.
float distanceY = Math.abs(playerOneCardMove.getTop() - playerOneCard.getTop());
float distanceX = Math.abs(playerOneCard.getLeft() - playerOneCardMove.getLeft());
TranslateAnimation translateAnimation = new TranslateAnimation(Animation.ABSOLUTE,distanceX ,Animation.ABSOLUTE,(distanceY) - (distanceY*2));
translateAnimation.setDuration(1000);
translateAnimation.setFillAfter(false);
playerOneCardMove.startAnimation(translateAnimation);
Hope this helps someone else.

How to move sprites from the Top to Bottom using Cocos2d Android?

I am trying to move a sprite from the top to bottom of the screen but I do not have any success at this moment... I've used the following as example.
In this case, the sprites, are moving from left to right, and in my case I want to move them from top to bottom.
Can anyone give me a help on this?
How can I proceed to make this work?

Use CCMoveToAction for moving a sprite.
For the movement of sprite from top to bottom
//to get total size of display
CGSize winSize = CCDirector.sharedDirector().displaySize();
CCMoveTo moveTo = CCMoveTo.action(1,
CGPoint.ccp(width, ));

Rotate a Scaled Image From the Center

I have some sprites (Well, custom classes that implement Sprite, but whatever) that I resize. AndEngine resizes the image from the center, which makes an image placed at 0,0 no longer appear at 0,0. To fix this I applied
sprite.setScaleCenterX(0);
sprite.setScaleCenterY(0);
This places the image where I want it. However, now when I rotate the image, the image moves around (If the image were a plain square, rotating it should make no visible change). To fix this I applied
sprite.setRotationCenterX((sprite.getWidth() * sprite.getScaleX()) / 2);
sprite.setRotationCenterY((sprite.getHeight() * sprite.getScaleY()) / 2);
(For some reason, resizing a Sprite doesn't change the dimensions of the sprite, just the visual image, hence multiplying it by the scale). This, however, did not correct the problem, but merely changed where the image moved to when flipped.
Is my math off here? Wouldn't this center the rotation on the image so that the image doesn't move position? Or is there something else I'm missing?
Below is full code:
Sprite sprite = new Sprite(0, 0, singleTrackTR, getVertexBufferObjectManager());
sprite.setScale(scaleX, scaleY);
sprite.setScaleCenterX(0);
sprite.setScaleCenterY(0);
sprite.setRotationCenterX((sprite.getWidth() * sprite.getScaleX()) / 2);
sprite.setRotationCenterY((sprite.getHeight() * sprite.getScaleY()) / 2);

All your code is correct. I tried it myself, both the setProperty(x, y) and the setPropertyX/Y(a) versions.
By any chance, do you have it connected to a Body? Note that the Body also doesn't scale with a Sprite's setScale. It has its own setTransform method, which takes x and y (that you both have to divide by PhysicsConstants.PIXEL_TO_METER_RATIO_DEFAULT) and a rotation value.

Android screen coordinate system : how to set (0,0) at the bottom left side of android screen as first quadrent of xy plane

how to set the screen coordinate system of android screen as first Quadrant of the XY plane
,iwant the (0,0) position to be at bottom left , and i wanna know if i can use the trignometric equation on android screen as Android XY plane is not like the Xy plane

I don't think there's a way to do it that would affect the entire system, such as the XML layout files. But if you just want to draw with a Canvas, you can use translate() and scale().
First use translate() to slide the canvas down so 0,0 is at the bottom. Now the top of the screen would be a negative number, so call scale() to flip it around. Now 0,0 is still at the bottom, and the top of the screen is a positive number.
I'm working with information from this answer and its comments. Use something like:
canvas.save(); // need to restore after drawing
canvas.translate(0, canvas.getHeight()); // reset where 0,0 is located
canvas.scale(1, -1); // invert
... // draw to canvas here
canvas.restore(); // restore to normal
And yes, you can use normal 2D trigonometric functions with the XY coords. You can do it even if they're not translated, you just have to think it through more carefully.

I don't know that you're going to have much luck changing where (0,0) is located, but you could set a constant that accounts for such. myY = y minus screenHeight so (x, myY) adjusts y to the bottom of the screen and works from there +/-.

look up canvas.scale(xs,ys,xp,yp)
xp and yp are the new coordinates that you set for your (0,0) point.