I have a Camera class that basically follows the player around the map and keeps him centered on the screen. The math im applying works great until the scale(Zooming in and OUt) of the camera is altered. Here it is:
x = -cell.x - cell.mass/2 + Game.width/2 / sX;
// Where x is the Camera's X, Cell is the Player and sX is the scale factor
I've been playing around with different equations but they all fail once the scale is altered. I can't seem to wrap my head around this and I could really use some insight on how to factor it in.
Here are some bits of the Camera Class:
public void set(Graphics bbg){
Graphics2D g2 = (Graphics2D)bbg;
g2.translate(x, y);
g2.scale(sX, sY);
}
public void unset(Graphics bbg){
Graphics2D g2 = (Graphics2D)bbg;
g2.translate(-x, -y);
}
public void scale(double sx, double sy){
sX = sx;
sY = sy;
}
public void Update(Cell cell){
scale(0.9,0.9);
x = -cell.x - cell.mass/2 + Game.width/2 / sX;
y = -cell.y - cell.mass/2 + Game.height/2 / sY;
}
public double toWorldX(int x){
return x - this.x / sX;
}
public double toWorldY(int y){
return y - this.y / sY;
}
The first image displays the result when the scale factor is 1(Normal Zoom). The second image displays the result when the scale factor is 0.9(Zoomed Out).
I'm having a little difficulty in determining what some of your variables mean (such as cell.mass, I'm assuming it is the size) and I assume that Game.width is the actual width of the window. It would help to know what EXACTLY happen when the zoom is changed (like is the "center" of the zoom at a particular corner of the screen).
Now for an answer, without know what happens to the actual zoom... have you tried the addition of parenthesis like this...
x = ((cell.x + cell.mass/2) - Game.width/2) / sX;
or (because you use '-' a lot, I'm not sure how your coordinates work)
x = ((-cell.x - cell.mass/2) + Game.width/2) / sX;
Just an idea.
The working equation for making the camera follow a player while factoring a scale factor is:
x =((cell.x + cell.mass * 0.5) - Game.width/sX * 0.5);
Related
The issue I have is that I'm attempting to add drag to an object in this basic physics simulation (Java [Processing]), but once I add the appropriate formula, it causes the objects velocity to increase drastically in the opposite direction. Of course the problem is that drag for some reason is being calculated too high but I'm not sure why thats happening as I'm using the real world equation.
void setup(){size(1280,720);}
class Circle{
float x,y,r,m,dx,dy,ax,ay,fx,fy;
Circle(float xPos, float yPos, float Radius, float Mass){
x = xPos;
y = yPos;
r = Radius;
m = Mass;
}
void ADD_DRAG(){
fx -= 0.5 * 1.225 * dx * dx * 0.5 * r * PI;
fy -= 0.5 * 1.225 * dy * dy * 0.5 * r * PI;
}
void update(){
ADD_DRAG();
ax = fx / m;
ay = fy / m;
dx += ax / frameRate;
dy += ay / frameRate;
x += dx / frameRate;
y += dy / frameRate;
}
}
Circle[] SceneObjects = {new Circle(50,50,20,20000),new Circle(50,50,2,20)};
void draw(){
background(51);
for (Circle c : SceneObjects){
c.update();
circle(c.x * 3,c.y * 3,c.r * 3);
}
}
void mouseClicked(){
if(SceneObjects[1].fx != 2000)
SceneObjects[1].fx = 2000;
else
SceneObjects[1].fx = 0;
}
This is the code, essentially there is a Circle class which stores the objects properties and then the forces applies are updated each draw loop. The mouseClicked void is just for testing by adding a force to the objects. All and any help is appreciated, thanks!
Maths I am Using:
Rearranged F=ma for ax = fx / m;
Acceleration * time = Speed for dx += ax / frameRate; (frameRate is 1/time)
Distance = Speed * time = for x += dx / frameRate; (same as above)
For drag im using this equation https://www.grc.nasa.gov/WWW/K-12/rocket/drageq.html with the constants eg air density etc added as seen.
There are a couple of things wrong here.
You haven't given us numbers (or a minimal complete example), but the vector algebra is off.
Yes, the acceleration is f = -kv2, and |v|2 = vx2 + vy2, but that doesn't mean that you can decompose f into fx=kvx2 and fy=kvy2. Not only is your magnitude off, but your acceleration is now not (in general) aligned with the motion; the path of your projectile will tend to curve toward a diagonal between the axes (e.g. x=y).
Also, your code always gives acceleration in the negative x and negative y directions. If your projectile happens to start out going that way, your version of air resistance will speed it up.
Finally, your time interval may simply be too large.
There is a better way. The differential equation is v' = -k v|v|, and the exact solution is v = (1/kt) z, (with appropriate choice of the starting time) where z is the unit direction vector. (I don't know how to put a caret over a letter.) This leads to v(t) = (1/t)v(t=1.0)
So you can either work out a fictional time t0 and calculate each new velocity using 1/(kt), or you can calculate the new velocity from the previous velocity: vn+1 =vn/(kd vn + 1), where d is the time interval. (And then of course you have to decompose v into vx and vy properly.)
If you're not familiar with vector algebra, this may seem confusing, but you can't get an air-resistance sim to work without learning the basics.
Is there some sort of formula for rotating the arrow in this link right here to make sure it's always pointing toward the red? Each time I've tried, I'd always get a number that's off, and the arrow's rotation is not in sync with the arrow's turning and movement.
A couple of snippets of code to show what I'm working with:
arrow.moveX(true);
arrow.moveY(true);
if(arrow.turning) {
arrow.turn(player.direction / (0.75 * arrow.getSpeed()));
}
The arrow's speed is 12.5 units/time if that's important. As for the movement itself:
public void moveX(boolean turn) {
if(turn) {
x += speed * Math.cos(angle);
} else {
x += speed;
}
}
public void moveY(boolean turn) {
if(turn) {
y += speed * Math.sin(angle);
} else {
y += speed;
}
}
I'm trying to figure out how to render the arrow's sprite make sure that the pointer itself is facing that "forward" direction that it's moving in, no matter how much it rotates. Here is the render method itself if that's necessary:
#Override
public void render(Canvas c, Paint p) {
matrix.setTranslate((float)x, (float)y);
if(alive) {
matrix.postRotate(drawnAngle, (float) (x + width / 2), (float) (y + height / 2));
} else {
matrix.postRotate(angle, (float) (x + width / 2), (float) (y + height / 2));
angle += speed * 2;
}
c.drawBitmap(getSprite(), matrix, p);
}
The variable drawnAngle has a value of 0 right now, it's a placeholder. It was just my attempt of trying to find the right number to rotate the arrow by.
So I've actually spent hours trying to figure this out, and the moment I decide to post for help, I figured it out! It turns out that while I was using radians in the first snippet of code (the actual movement), I was supposed to be using degrees in the actual rotate in that last snippet!
I changed drawnAngle to (float)(angle * (180 / Math.PI)) and this worked as a solution for me!
Hopefully no one else has this problem.
I'm trying to draw a circle on my canvas. Pseudocode of my algorithm looks like that
double R = 1.0;
// Draw 11 points, lying on the circle with the radius of 1
// and angle from 0 to 90 degrees
for(int i=0; i<=10; i++)
{
drawPoint( R*cos(PI*i/20), R*sin(PI*i/20) );
}
// Draw a circle with center at the (0; 0) and with the radius of 1
drawCircle(0, 0, R);
That's what I've got:
Looks fine, but there is one problem. When I increase radius only points with angles 0, 45 and 90 lie on a circle.
That's how it looks 72 degrees:
There is no any info about accuracy of the method drawCircle on developer.android.com.
I guess that it draws, based on the values at points with angles 0, 45, 90, ..., and calculate line in other positions very approximately.
I know, that I can draw circle as accurate as I want to, if I'll draw it like a polyline with tiny step, but it will work very slow.
So I want to find out - is there any methods to draw circle accurate in Android?
UPD 1:
How do I draw a points:
int x, y;
x = getPixelX(point.getX());
y = getPixelY(point.getY());
canvas.drawCircle(x, y, point.radius, paint);
Where getPixelX and getPixelY takes a coorditate of the point on plane and returns the same coordinate on the screen, basing on scale and offset.
I thought that I could make some mistake in those methods, but they work perfectly with the lines. I can zoom in lines and there is no error, all the points lies just on the line.
UPD 2:
There are comments, that probably I make a mistake in my calculations. I do not argue, perhaps you're right. So here is my "calculations".
How do I zoom in:
public void mouseWheelMoved(MouseWheelEvent e) {
// zoomQ is 0.9 or 1.1
double zoomQ = (e.getWheelRotation() + 10) / 10.0;
scaleX *= zoomQ;
scaleY *= zoomQ;
}
How do I move the plane:
public void mouseDragged(MouseEvent e) {
centerX -= (e.getX() - lastMouseX)/scaleX;
centerY -= (e.getY() - lastMouseY)/scaleY;
lastMouseX = e.getX();
lastMouseY = e.getY();
}
How do getPixelX/Y works:
public int getPixelX(double planeX) {
return (int)Math.round( scaleX*(planeX - centerX) + ScreenWidth/2 );
}
public int getPixelY(double planeY) {
return (int)Math.round( scaleY*(planeY - centerY) + ScreenHeight/2 );
}
Alright, I'm trying to do some simple object moving in the direction of where you touched the screen.
If I touch directly northwest of the object, it'll kind of move into the direction of the touch position. If I touch directly southeast of the object, it will kind of move into the direction of the touch position as well. However, if I touch directly northeast of the object, it'll move into the opposite direction towards the southwest. If I touch directly southwest of the object, it'll also move to the opposite direction towards northeast.
Also, if I touch north of the object, but just a little to the west, it will go straight west with a little to the north. Same with touching west of the object with a little bit to the north, it'll go straight north with a little bit to the west. Same thing for other directions.
Really, all the directions are from somewhat to obviously incorrect. I've been doing some paper calculations as well and I've seemed to be getting some correct angles, but at this point I'm completely stumped.
Does anyone know what the problem may be?
package com.badlogic.androidgames.texasholdem;
import java.util.List;
import android.util.FloatMath;
import com.badlogic.androidgames.framework.Game;
import com.badlogic.androidgames.framework.Graphics;
import com.badlogic.androidgames.framework.Input.TouchEvent;
import com.badlogic.androidgames.framework.Screen;
public class MainMenuScreen extends Screen {
public static float TO_RADIANS = (1 / 180.0f) * (float) Math.PI;
public static float TO_DEGREES = (1 / (float) Math.PI) * 180;
float num_x = 0; // Position of object on X axis
float num_y = 0; // Position of object on Y axis
float angle = 0;
public MainMenuScreen(Game game) {
super(game);
}
public void update(float deltaTime) {
Graphics g = game.getGraphics();
List<TouchEvent> touchEvents = game.getInput().getTouchEvents();
game.getInput().getKeyEvents();
int len = touchEvents.size();
for(int i = 0; i < len; i++) {
TouchEvent event = touchEvents.get(i);
if(event.type == TouchEvent.TOUCH_UP) {
if(inBounds(event, 0, 0, g.getWidth(), g.getHeight()) ) {
// Calculate the angle of the direction between two points
angle = (float) Math.atan2(event.x - num_x, event.y - num_y) * TO_DEGREES;
if (angle < 0)
angle += 360;
// This is just to give me numbers on the Math.atan2 result, angle, to/from X position, and to/from Y position
System.out.println("Pressed! - ATAN: " + Math.atan2(event.x - num_x, event.y - num_y)
+ " - ANGLE:" + angle + " - POS: " + event.x + "tx/"
+ (int)num_x + "fx " + event.y + "ty/" + (int)num_y + "fy");
}
}
}
// Moving object in direction at 1f speed
num_x += (1f * (float) Math.cos(angle * TO_RADIANS));
num_y += (1f * (float) Math.sin(angle * TO_RADIANS));
}
private boolean inBounds(TouchEvent event, int x, int y, int width, int height) {
if(event.x > x && event.x < x + width - 1 &&
event.y > y && event.y < y + height - 1)
return true;
else
return false;
}
public void present(float deltaTime) {
Graphics g = game.getGraphics();
g.drawPixmap(Assets.background, 0, 0);
g.drawPixmap(Assets.backcard, (int)num_x, (int)num_y);
}
public void pause() {
Settings.save(game.getFileIO());
}
public void resume() {
}
public void dispose() {
}
}
if event x> x then x must be positive to move toward event.x
the problem here is that when event.x< x then your moving x must be negative
int dx,dy;
dx = (1f * (float) Math.cos(angle * TO_RADIANS));
dy = (1f * (float) Math.sin(angle * TO_RADIANS));
if(event.x<x){
dx=-dx;}
if(event.y<y){
dy=-dy;}
num_x+=dx;
num_y+=dy;
this way is simpler but less precise....
public void update(){
//(find dif between item x, and touch x)
float xdif=destx-x;
float ydif=desty-y;
if(x<destx){
dx=xdif/8;
}
else if(x>destx){
//we devide both x and y differences by the same number
dx=xdif/8;
}
else if(x==destx){
dx=0;
}
if(y<desty){
dy=ydif/5;
}
else if(y>desty){
dy=ydif/5;
}
else if(y==desty){
dy=0;
}
x+=dx;
y+=dy;
there u go, pathing in a straight line between two points, item.x and touch x.
Firstly, the math - I think the problem is that, for example, tan(135deg) = tan (-45deg) = -1. Therefore, atan has return values ranging between -90deg and 90deg as a resolution to ambiguity (look at its graph here). I think La5t5tarfighter's solution - negating the x movement in some cases - is on the right track, but you need to negate the y component in those cases as well. You could try that, but it would be much simpler if you used libGDX's Vector2 class. This is how I'd do it:
move.set(touchX, touchY); // y should be through flipping or unproject() before this
move.sub(objectPos); // move now points from object to where you touched
move.nor(); // now 1 unit long
move.scl(SPEED*deltaTime); // multiplied by a constant and delta - framerate-independent
objectPos.add(move);
You could even chain it into just one line if you want:
objectPos.add(move.set(x,y).sub(objectPos).nor().scl(SPEED*deltaTime));
Secondly, you're not using a Camera. I'm not completely sure what the default coordinate system is, but I believe the y axis points up which is not the same as the one used for inputs - Input.getY() is given with an y axis pointing down from the top left corner. If you had a Camera, you'd do this:
cam.unproject(someVector.set(Gdx.input.getX(), Gdx.input.getY(), 0));
Lacking that, you might need to flip the y axis:
event.y = Gdx.graphics.getHeight() - event.y;
Still, this could be wrong. Try drawing the object right at the touch position - if I'm right in this, it'll seem mirrored vertically. If it draws correctly where you touch, ignore this part.
I am trying to move a Sprite along a straight line path. I want to move it 5 pixels on the slope, or the hypotenuse each time I go through the method until I reach the end point.
I have the slope and y-intercept of the line, I also have the current X and Y values of the sprite through getX() and getY(). The final X and Y points to stop at are variables finalX and finalY.
I have tried so many equations but I can't seem to get any of them to work. What am I missing!!?
My latest equation was trying to use y=mx+b.
float X = (getY() + 5 - interceptY)/slope;
float Y = slope*(getX() + 5) + interceptY;
setPosition(X, Y);
Can help you with a few equations from my recent game, the code moves an object given its rotation:
float xDirection = FloatMath.sin((float) Math.toRadians(getRotation()))
* currentSpeed;
float yDirection = FloatMath.cos((float) Math.toRadians(getRotation()))
* -currentSpeed;
float newX = getX() + xDirection;
float newY = getY() + yDirection;
You just need to derive the angle in which you need your sprite to move and this will do for you. Hope this helps.