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I am trying to make a 2D tile-based top-down game in XNA. It is 16 x 16 tiles, and each tile is 25 pixels.
I have a character sprite starting at (0, 0) first tile, and I'm trying to make it movable using the keyboard from tile to tile. So in the Update method, when the arrow key is pressed, I tried adding or subtracting 25 to x or y of the position vector. It seems to be aligned in the tiles when moving, but it's moving about 4-5 tiles instead of just 1 tile at a time. I have tried multiplying it with gameTime.TotalGameTime.TotalSeconds, but it doesn't seem to help.
I'm kind of new to using XNA. Does anyone have any tutorials or can help with how to calculate the movement? Thanks in advance.
If you just check IsKeyDown every frame, it will say it is down on each frame that it is held down. At 60 frames-per-second, pressing a key will result in it being in the down state for several frames. Hence on each frame you are moving your character! By the time you let go of the key - he'll have moved several squares.
If you want to detect each key press (the key entering the "down" state), you need something like this:
KeyboardState keyboardState, lastKeyboardState;
bool KeyPressed(Keys key)
{
return keyboardState.IsKeyDown(key) && lastKeyboardState.IsKeyUp(key);
}
override void Update(GameTime gameTime)
{
lastKeyboardState = keyboardState;
keyboardState = Keyboard.GetState();
if(KeyPressed(Keys.Right)) { /* do stuff... */ }
}
However if you want to add a "repeat" effect when holding down the key (like what happens in typing), you need to count the time - something like this:
float keyRepeatTime;
const float keyRepeatDelay = 0.5f; // repeat rate
override void Update(GameTime gameTime)
{
lastKeyboardState = keyboardState;
keyboardState = Keyboard.GetState();
float seconds = (float)gameTime.ElapsedGameTime.TotalSeconds;
if(keyboardState.IsKeyDown(Keys.Right))
{
if(lastKeyboardState.IsKeyUp(Keys.Right) || keyRepeatTime < 0)
{
keyRepeatTime = keyRepeatDelay;
// do stuff...
}
else
keyRepeatTime -= seconds;
}
}
When you use IsKeyDown, you don't have to use timers.
public void HandleInput(KeyboardState keyState)
{
if (keyState.IsKeyDown(Keys.Left))
{
//go left...
}
}
Related
this is my first time of asking a question in stackoverflow, sorry if my english is not really good. I hope this is a good start.
I am currently trying to use my stm32's key button/ user button (i mean the one button which already included on it in buying written "key") and i want to use the button to do some project. I did some research and found the key button is on pin A0, so i labelled it to BUTTON. So i try to check if the button is functioning using this code:
on private variable section
int a; //variable declare
on while section
while (1){
a = 0
if (HAL_GPIO_ReadPin(BUTTON_GPIO_Port, BUTTON_Pin)){
a = 1;
} else {
a = 0;
}
}
i'm expecting that when i debug the code and then see the live variable, i will find that variable "a" is gonna turn into 1 when i press the key button, but it is not working as i expected. The variable "a" is still on 0 whatever i do.
im kinda desperate, please help, i appreciate all of the answer :D.
You are setting a = 0; every time around the loop. It might briefly be set to 1 if the button is pressed, but then it will be set back to zero.
Also, the compiler may well detect that the variable a is not actually used for anything, so it might just optimize out the setting of a.
Lastly, HAL_GPIO_ReadPin() can return GPIO_PIN_RESET or GPIO_PIN_SET. So you should test that it is one of those.
Try this:
volatile int a = 0; // Tell compiler not to optimize out setting of 'a'
while (1) {
// No need to set 'a' to zero here
if (HAL_GPIO_ReadPin(BUTTON_GPIO_Port, BUTTON_Pin) == GPIO_PIN_SET){
a = 1;
} else {
a = 0;
}
}
I am playing around, trying to make a little JavaFX application to visualize data received via the serial port from an arduino-based board and some sensors.
After adding some live-updating LineGraphs, I am currently trying to display the roll, pitch and yaw values received from the micro-controller, by rotating a simple box-element.
I have one thread calling a function every x ms, which stores the incoming data into an ObservableList with an changeListener and calls the controller based function to update/rotate the orientation of the box.
Since the calculation of the angles is allready done on the micro-controller, I would like to rotate the box to the received absolute orientation.
From what I've understand so far, I can't simply rotate from any previous orientation to a new absolute one, but only change the orientation relatively to the previous one.
I came up with the following idea to just subtract the last roll/pitch/yaw values from the penultimate one of the observableList.
Data dataTmp = observableList.get(observableList.size()-2);
Data dataTmp2 = observableList.get(observableList.size()-1);
newRoll = dataTmp2.getRoll() - dataTmp.getRoll();
newPitch = dataTmp2.getPitch() - dataTmp.getPitch();
newYaw = dataTmp2.getYaw() - dataTmp.getYaw();
Platform.runLater(new Runnable() {
#Override
public void run() {
controller.setToPosition(newRoll, newPitch, newYaw);
}
});
//...
This only works out to a certain extent. I still want to rotate to the absolute position received from the micro-controller.
So my question is this: Is there a way to reset the orientation of the box to e.g. 0, 0, 0 from where I could rotate to my new absolute orientation? Simply removing the box and adding a new one did not work out at all.
group.getChildren().remove(box);
box = new Box(300,50,300);
group.getChildren().add(box);
Thank you in advance for any ideas or even solutions. If you need more information or code snippets let me know.
Referring to this example, an onMouseMoved handler rotates the red Box around the x and y axes as the mouse moves. The following onKeyPressed handler restores the red Box to its original position when the Z key is pressed. Each handler uses the setAngle() method of the Rotate class.
scene.setOnKeyPressed(e -> {
if (e.getCode() == KeyCode.Z) {
content.rx.setAngle(0);
content.ry.setAngle(0);
content.rz.setAngle(0);
}
});
Similarly, your setToPosition() implementation can invoke setAngle() to establish the new roll, pitch and yaw values.
Before:
After:
More subtly, verify that you synchronize access to any data shared between your data acquisition thread and the JavaFX application thread. This example illustrates a Task<Canvas>, while your application might instead implement a Task<Point3D>, where a Point3D holds the roll, pitch and yaw values.
I have a drone following a path for movement. That is, it doesn't use a rigidbody so I don't have access to velocity or magnitude and such. It follows the path just fine, but I would like to add banking to it when it turns left or right. I use a dummy object in front of the drone, thinking I could calculate the bank/tilt amount using the transform vectors from the two objects.
I've been working on this for days as I don't have a lot of math skills. Basically I've been copying pieces of code trying to get things to work. Nothing I do works to make the drone bank. The following code manages to spin (not bank).
// Update is called once per frame
void Update () {
Quaternion rotation = Quaternion.identity;
Vector3 dir = (dummyObject.transform.position - this.transform.position).normalized;
float angle = Vector3.Angle( dir, transform.up );
float rollAngle = CalculateRollAngle(angle);
rotation.SetLookRotation(dir, transform.right);// + rollIntensity * smoothRoll * right);
rotation *= Quaternion.Euler(new Vector3(0, 0, rollAngle));
transform.rotation = rotation;
}
/// <summary>
/// Calculates Roll and smoothes it (to compensates for non C2 continuous control points algorithm) /// </summary>
/// <returns>The roll angle.</returns>
/// <param name="rollFactor">Roll factor.</param>
float CalculateRollAngle(float rollFactor)
{
smoothRoll = Mathf.Lerp(smoothRoll, rollFactor, rollSmoothing * Time.deltaTime);
float angle = Mathf.Atan2(1, smoothRoll * rollIntensity);
angle *= Mathf.Rad2Deg;
angle -= 90;
TurnRollAngle = angle;
angle += RollOffset;
return angle;
}
Assuming you have waypoints the drone is following, you should figure out the angle between the last two (i.e. your "now-facing" and "will be facing" directions). The easy way is to use Vector2.Angle.
I would use this angle to determine the amount I'll tilt the drone's body: the sharper the turn, the harder the banking. I would use a ratio value (public initially so I can manipulate it from the editor).
Next, instead of doing any math I would rely on the engine to do the rotation for me - so I would go for Transform.Rotate function.In case banking can go too high and look silly, I would set a maximum for that and Clamp my calculated banking angle between zero and max.
Without knowing exactly what you do and how, it's not easy to give perfect code, but for a better understand of the above, here's some (untested, i.e. pseudo) code for the solution I visualize:
public float turnSpeed = 7.0f; //the drone will "rotate toward the new waypoint" by this speed
//bankSpeed+turnBankRatio must be two times "faster" (and/or smaller degree) than turning, see details in 'EDIT' as of why:
public float bankSpeed = 14.0f; //banking speed
public float turnBankRatio = .5f; //90 degree turn == 45 degree banking
private float turnAngle = 0.0f; //this is the 'x' degree turning angle we'll "Lerp"
private float turnAngleABS = 0.0f; //same as turnAngle but it's an absolute value. Storing to avoid Mathf.Abs() in Update()!
private float bankAngle = 0.0f; //banking degree
private bool isTurning = false; //are we turning right now?
//when the action is fired for the drone it should go for the next waypoint, call this guy
private void TurningTrigger() {
//remove this line after testing, it's some extra safety
if (isTurning) { Debug.LogError("oups! must not be possible!"); return; }
Vector2 droneOLD2DAngle = GetGO2DPos(transform.position);
//do the code you do for the turning/rotation of drone here!
//or use the next waypoint's .position as the new angle if you are OK
//with the snippet doing the turning for you along with banking. then:
Vector2 droneNEW2DAngle = GetGO2DPos(transform.position);
turnAngle = Vector2.Angle(droneOLD2DAngle, droneNEW2DAngle); //turn degree
turnAngleABS = Mathf.Abs(turnAngle); //avoiding Mathf.Abs() in Update()
bankAngle = turnAngle * turnBankRatio; //bank angle
//you can remove this after testing. This is to make sure banking can
//do a full run before the drone hits the next waypoint!
if ((turnAngle * turnSpeed) < (bankAngle * bankSpeed)) {
Debug.LogError("Banking degree too high, or banking speed too low to complete maneuver!");
}
//you can clamp or set turnAngle based on a min/max here
isTurning = true; //all values were set, turning and banking can start!
}
//get 2D position of a GO (simplified)
private Vector2 GetGO2DPos(Vector3 worldPos) {
return new Vector2(worldPos.x, worldPos.z);
}
private void Update() {
if (isTurning) {
//assuming the drone is banking to the "side" and "side" only
transform.Rotate(0, 0, bankAngle * time.deltaTime * bankSpeed, Space.Self); //banking
//if the drone is facing the next waypoint already, set
//isTurning to false
} else if (turnAngleABS > 0.0f) {
//reset back to original position (with same speed as above)
//at least "normal speed" is a must, otherwise drone might hit the
//next waypoint before the banking reset can finish!
float bankAngle_delta = bankAngle * time.deltaTime * bankSpeed;
transform.Rotate(0, 0, -1 * bankAngle_delta, Space.Self);
turnAngleABS -= (bankAngle_delta > 0.0f) ? bankAngle_delta : -1 * bankAngle_delta;
}
//the banking was probably not set back to exactly 0, as time.deltaTime
//is not a fixed value. if this happened and looks ugly, reset
//drone's "z" to Quaternion.identity.z. if it also looks ugly,
//you need to test if you don't """over bank""" in the above code
//by comparing bankAngle_delta + 'calculated banking angle' against
//the identity.z value, and reset bankAngle_delta if it's too high/low.
//when you are done, your turning animation is over, so:
}
Again, this code might not perfectly fit your needs (or compile :P), so focus on the idea and the approach, not the code itself. Sorry for not being able right now to put something together and test myself - but I hope I helped. Cheers!
EDIT: Instead of a wall of text I tried to answer your question in code (still not perfect, but goal is not doing the job, but to help with some snippets and ideas :)
So. Basically, what you have is a distance and "angle" between two waypoints. This distance and your drone's flight/walk/whatever speed (which I don't know) is the maximum amount of time available for:
1. Turning, so the drone will face in the new direction
2. Banking to the side, and back to zero/"normal"
As there's two times more action on banking side, it either has to be done faster (bankSpeed), or in a smaller angle (turnBankRatio), or both, depending on what looks nice and feels real, what your preference is, etc. So it's 100% subjective. It's also your call if the drone turns+banks quickly and approaches toward the next waypoint, or does things in slow pace and turns just a little if has a lot of time/distance and does things fast only if it has to.
As of isTurning:
You set it to true when the drone reached a waypoint and heads out to the next one AND the variables to (turn and) bank were set properly. When you set it to false? It's up to you, but the goal is to do so when the maneuver is finished (this was buggy in the snippet the first time as this "optimal status" was not possible to ever be reached) so he drone can "reset banking".For further details on what's going on, see code comments.Again, this is just a snippet to support you with a possible solution for your problem. Give it some time and understand what's going on. It really is easy, you just need some time to cope ;)Hope this helps! Enjoy and cheers! :)
I recently had an interview with Microsoft for an internship and I was asked this question in the interview.
Its basically like, you have 2 parallel staircases and both the staircases have n steps. You start from the bottom and you may move upwards on either of the staircases. Each step on the staircase has a penalty attached to it.
You can also move across both the staircases with some other penalty.
I had to find the minimum penalty that will be imposed for reaching the top.
I tried writing a recurrence relation but I couldn't write anything because of so many variables.
I recently read about dynamic programming and I think this question is related to that.
With some googling, I found that this question is the same as
https://www.hackerrank.com/contests/frost-byte-final/challenges/stairway
Can you please give a solution or an approach for this problem ?
Create two arrays to keep track of the minimal cost to reach every position. Fill both arrays with huge numbers (e.g. 1000000000) and the start of the arrays with the cost of the first step.
Then iterate over all possible steps, and use an inner loop to iterate over all possible jumps.
foreach step in (0, N) {
// we're now sure we know minimal cost to reach this step
foreach jump in (1,K) {
// updating minimal costs here
}
}
Now every time we reach updating there are 4 possible moves to consider:
from A[step] to A[step+jump]
from A[step] to B[step+jump]
from B[step] to A[step+jump]
from B[step] to B[step+jump]
For each of these moves you need to compute the cost. Because you already know that you have the optimal cost to reach A[step] and B[step] this is easy. It's not guaranteed this new move is an improvement, so only update the target cost in your array if the new cost is lower then the cost already there.
Isn't this just a directed graph search? Any kind of simple pathfinding algorithm could handle this. See
https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
https://en.wikipedia.org/wiki/A*_search_algorithm
Just make sure you enforce the directional of the stairs (up only) and account for penalties (edge weights).
Worked solution
Of course, you could do it with dynamic programming, but I wouldn't be the one to ask for that...
import java.io.;
import java.util.;
public class Main {
public static int csmj(int []a,int src,int[] dp){
if(src>=a.length){
return Integer.MAX_VALUE-1;
}
if(src==a.length-1){
return 0;
}
if(dp[src]!=0){
return dp[src];
}
int count=Integer.MAX_VALUE-1;
for(int i=1;i<=a[src];i++){
count = Math.min( count , csmj(a,src+i,dp)+1 );
}
dp[src] = count;
return count;
}
public static void main(String args[] ) throws Exception {
Scanner s = new Scanner(System.in);
int n = s.nextInt();
int a[] = new int[n];
for(int i=0;i<n;i++){
a[i] = s.nextInt();
}
int minJumps = csmj(a,0,new int[n]);
System.out.println(minJumps);
}
}
bro you can have look at that solution my intuition is that
Hi first time posting here. I searched and found how re-implementing the QSpinBox class allows for custom uses. However I am not sure if my needs are addressed in as much as what I found by re-implementing the validate method.
I need a custom range that excludes a zero value in the range of values. The spinner is used for selecting zoom ratio for a loaded image. The initial range at design time is -25 to 10. That range could change depending on the dimensions of the image. Nevertheless, I have to be able to "skip" zero for a desired zoom factor. For example, the range would have to always be going from -1 to 1 or vice-versa.
I assume you're listening to QSpinbox::valueChanged(int i) signal, there you can do something like this:
void zoomImage(int i) {
if (i == 0) {
if (lastValue < 0) //if sliding from negative values
spinBox->setValue(1);
else
spinBox->setValue(-1);
return; //skip processing for 0
}
else
lastValue = i; //save last state to a class variable
//processing...
}
EDIT: int lastValue is used for storing the position of slider before it hits 0 in order to determine if the user slides to negative or positive values
What seems to have worked:
void MainWindow::zoomImage(int ctlValue)
{
if(ctlValue == 0)
{
if(zoomLastValue < 0)
ui->sbScaleImage->stepBy(1);
else
ui->sbScaleImage->stepBy(-1);
}
zoomLastValue = ui->sbScaleImage->value();
}
Apologies if I screwed up the formatting.