Thread: Moving object in the y-axis

Hi guys,

I'm new in this forum and I'm using it to help me in my coding classes.

I just have one problem with a "car" program in java.
The objective is to move the car in the direction it is facing.
Moving forward in the normal position (when the angle is zero) means moving in the x-axis. Choosing to turn the car function (for example: 90º) and then using the forward function should move up or down the car in the y-axis. However the y-axis is not working.
I will leave here the code in bluej and what teacher wants me to do...


I hope that someones can teach me how to do this... I'm stuck.



PS: I don't know if someone in forum already posted this.
Car2 Demo.rarThe Problem to be solved.JPGmyanswer.JPGMoveforwardfunction.jpg

Welcome to the forum! Please read this topic to learn how to post code in code or highlight tags and other useful info for new members.

Sorry :\
Here it goes...

 public void moveForward(int dist)
    { 
        // Obtain the current rotation in degrees
        int rotationInDegrees  = carImage.getRotation();
        // Convert the current rotation from degrees to radians
        rotationInDegrees=0;
        double rotationInRadians = 0.0;
        rotationInRadians=Math.toRadians(rotationInDegrees); 
        IO.outputln("The result of radians is: "+rotationInRadians);
 
        // Calculate the distance to move in both x and y directions
        double distX=dist;
        double distY=0.0;
 
        distX=dist*Math.cos(Math.toRadians(rotationInRadians));
        distY=dist*Math.sin(Math.toRadians(rotationInRadians));
          IO.outputln("x= "+distX);
          IO.outputln("y= "+distY);
 
 
 
 
        // Move the car in both x and y directions with the correct distances
        // Notice that setX() and setY() take int as argument
         carImage.setX(carImage.getX() + (int)distX);
 
 
         carImage.setY(carImage.getY() + (int)distY);       
    }

 public void makeTurn(int angle) 
    { 
        // Change the orientation of car from current orientation plus angle
        carImage.setRotation(carImage.getRotation() + angle);
    }

How I can I move the car in the y-axis after using the "maketurn" function ?


Thanks

I'm assuming you have a paintComponent() method somewhere that draws the car starting at some x, y coordinate. To move the car across the drawing area to the right, you increase the x-coordinate and redraw the car. Similarly, to move the car up the drawing area, you'd decrease the y-coordinate and redraw the car. Decreasing x moves the car to the left, increasing y moves the car down. If you increase both x and y in equal proportions, then the car will move in a 45-degree direction towards the bottom right corner.

You'll want to determine the correct proportions in which to vary x and y according to the direction in which the car is pointed. Do you know basic trig, like sine and cosine?

Thanks for your fast reply.

The program doesn't use the paint component.
And yes, I know some basic trig, although it was very long time that I studied that.

And sorry because I forgot to post all the rest of the program, since the teacher only wants me to modify in the moveforward function

import comp102x.IO;
import comp102x.Canvas;
import comp102x.ColorImage;
public class Car2
{
 
    String owner = "NoName";
    ColorImage carImage = new ColorImage("Car1.png");
    double gasMileage = 10.0;
    double gasInTank = 10.0;
  public void Car2Demo()
    {
        Canvas canvas = new Canvas();
        canvas.add(carImage,200,200);
    }

The gasMileage and gasintank is for other functions. (just forget about them )
Hope it's more clear now.

And sorry that I didn't read Post #4 very carefully.

How I can I move the car in the y-axis after using the "maketurn" function ?

"Functions" in Java are called methods.

The makeTurn() method sets the car's rotation, then in the moveForward() method, the car's rotation is retrieved and applied to distX and distY which are then used to modify the car's x and y coordinates. What I don't see is where the car image is redrawn using the new coordinates. Either the carImage object should draw itself using the updated coordinates, or there should be a statement that updates the canvas object with the car image's new coordinates. I don't see where that's happening.

No matter what I do, the car only moves in the x-axis. It's like it's not recognizing the y-axis coordinates.

I suppose will be this

...
    carImage.setX(carImage.getX() + (int)distX);
         carImage.setY(carImage.getY() + (int)distY); 
..

But it's not working.

Can I show you by stream the running of car2demo ?

Can't you post the source code necessary to compile and run the app to witness what is/isn't happening?

Ok.

I will repost again all the code of car2 class (the class that I'm working in)

import comp102x.IO;
import comp102x.Canvas;
import comp102x.ColorImage;
 
/**
 * Write a description of class Cars here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Car2
{
 
    String owner = "NoName";
    ColorImage carImage = new ColorImage("Car1.png");
    double gasMileage = 10.0;
    double gasInTank = 10.0;
 
    public Car2 () {}
 
    public Car2(String nameOfOwner) 
    {
        owner = nameOfOwner;
        carImage = new ColorImage();
    }
 
    public Car2 (String nameOfOwner, double newGasMileage) 
    {
        owner = nameOfOwner;
        carImage = new ColorImage( );
        gasMileage = newGasMileage;
    }
 
    public void moveForward(int dist)
    { 
        // Obtain the current rotation in degrees
        int rotationInDegrees  = carImage.getRotation();
        // Convert the current rotation from degrees to radians
        rotationInDegrees=0;
        double rotationInRadians = 0.0;
        rotationInRadians=Math.toRadians(rotationInDegrees); 
        IO.outputln("The result of radians is: "+rotationInRadians);
 
        // Calculate the distance to move in both x and y directions
        double distX=dist;
        double distY=0.0;
 
        distX=dist*Math.cos(Math.toRadians(rotationInRadians));
        distY=dist*Math.sin(Math.toRadians(rotationInRadians));
          IO.outputln("x= "+distX);
          IO.outputln("y= "+distY);
        // Move the car in both x and y directions with the correct distances
        // Notice that setX() and setY() take int as argument
         carImage.setX(carImage.getX() + (int)distX);
         carImage.setY(carImage.getY() + (int)distY);
 
        // Update the amount of gas in tank assumming that each unit of dist is 10m
        double distKm = dist / 100.0;
        double gasUsed = distKm / 100.0 * gasMileage;
        gasInTank = gasInTank - gasUsed;
        IO.outputln("Amount of gas used: " + gasUsed + ", gas remained: " + gasInTank);
    }
 
    public void makeTurn(int angle) 
    { 
        // Change the orientation of car from current orientation plus angle
        carImage.setRotation(carImage.getRotation() + angle);
    }
 
    // addGas adds an amount of gas equal to gasToAdd to gasInTank
     public void addGas(double gasToAdd) {
         //gasInTank = gasInTank + gasUsed;
         gasInTank = gasInTank + gasToAdd;
    }
 
    public void Car2Demo()
    {
        Canvas canvas = new Canvas();
        canvas.add(carImage,200,200);
    }
 
}

The answer to my question is, "No, you can't because of the non-standard API on which the program relies and I can't find."

It's interesting that in the moveForward() method, distX is initialized to dist, but distY is initialized to 0.

Looking at the math closer:

rotationInDegrees=0;
double rotationInRadians = 0.0;
rotationInRadians=Math.toRadians(rotationInDegrees );

So rotationInRadians = 0.

distY=dist*Math.sin(Math.toRadians(rotationInRadia ns));

I don't understand why rotationInRadians is being converted to radians (again), so that might be wrong, but also, the sin( 0 ) is 0, so distY will always be 0.

You might try plugging in some appropriate constants for distY to see if that causes the Y-coordinate to change - or just use distX to start with. In other words, change this statement:

carImage.setY(carImage.getY() + (int)distY);

to:

carImage.setY(carImage.getY() + (int)distX);

Once you've done that and see that successfully changing the y-coordinate causes the image to move in the y direction, then you need to review the math to see what you've done wrong, if anything. (Not sure what you were given and what you've written.)

Good luck!

Greg

I tried this and now works
I took off the rotationinRadians=0.0; and did other small modifications
see

 public void moveForward(int dist)
    { 
 
 
        // Calculate the distance to move in both x and y directions
       double rotationInRadians=Math.toRadians(carImage.getRotation());
        double distX=dist*Math.cos(rotationInRadians);
        double distY=dist*Math.sin(rotationInRadians);
          IO.outputln("x= "+distX);
          IO.outputln("y= "+distY);
        // Move the car in both x and y directions with the correct distances
        // Notice that setX() and setY() take int as argument
         carImage.setX(carImage.getX() + (int)distX);
         carImage.setY(carImage.getY() + (int)distY); 
        // Update the amount of gas in tank assumming that each unit of dist is 10m
        double distKm = dist / 100.0;
        double gasUsed = distKm / 100.0 * gasMileage;
        gasInTank = gasInTank - gasUsed;
        IO.outputln("Amount of gas used: " + gasUsed + ", gas remained: " + gasInTank);
    }

Anyone can use this code if needed.
Thanks

Glad you figured it out.