I understand the theory behind Per Pixel Collision in Xna, you get the texture data from two textures, and then compare them, checking the alpha values of, for example, your character texture.
What I'm wanting to do is use Per Pixel Collision to check if the Player Sprite has touched the map by checking for collisions with a certain colour (Black). I've tried implementing this before, but the characters always falls through the map with no programming errors thrown.
Please point me towards articles/tutorials/videos, or if anybody here could give me some tips and points that would be great too.
I would not check pixel to pixel between two textures, if I were you. Checking just one point vs a map is not too bad, though;
//In Class-scope:
Color[] CollisionMapData;
Texture2D CollisionMap;
public void LoadContent()
{
CollisionMap = Content.Load<Texture2D>("map");
CollisionMapData = new Color[CollisionMap.Width * CollisionMap.Height];
CollisionMap.GetData<Color>(CollisionMapData);
}
public Boolean Collision(Vector2 position)
{
int index = (int)position.Y * CollisionMap.Width + (int)position.X;
if (index < 0 || index >= CollisionMapData.Length) //Out of bounds
return true;
if (CollisionMapData[index] == Color.Black)
return true;
return false;
}
To check the entire player-sprite against a map, you would have to call the Collision-method for each pixel in the players sprite, creating a vector2 to get the right point.
It is a lot easier to check maybe a few points (for instance; topleft, topmiddle, topright, left, right, bottomleft, bottommiddle, bottomright. No need to check middle because sides are already being tested.)
Related
My problem is pretty simple, but yet I struggle to find an answer. Brief context, I have a sprite that moves accross the Y-axis according to microphone input. Beforehand, I prompted the user to record their lowest and highest note, calculated the frequency of these two notes and am using it as a reference for positioning the sprite on the Y-axis.
Let's say the lowest note is 100 Hz and the highest one 400 Hz. So if the player makes a tone of 100 Hz, the sprite should move down to the bottom of the Y-axis. To move back to the center (Y-position 0), the player would have to make a tone of 250 Hz (midpoint between 100 and 400).
So we know that for that player, 250 Hz equals to Y-position 0. But I need to know the Y-position equivalents of the lowest note (bottom edge) and highest note (top edge). When I move the sprite manually to the top edge and look at the Y-value in the inspector, it's apparently 4.58. But I'm not sure if hard-coding 4.58 would scale well across different screen-sized devices.
Screenshot here: https://i.ibb.co/pjrkSNV/Capture.png
I ideally want to have a method called FrequencyToY(float frequency) that converts a frequency value to the corresponding Y-value on the axis. I saved the lowest and highest frequency values in PlayerPrefs. Important note about the sprite movement, I don't want gravity. The bird should just smoothly move to the corresponding Y-position every time the player produces a tone, and stay in place otherwise.
This is my current script attached to my sprite:
public class Player : MonoBehaviour
{
public AudioSource audioPlayer;
public AudioMixer masterMixer;
private float[] _spectrum;
private float _fSample;
private Transform playerTransform;
void Start()
{
playerTransform = transform;
//Code for microphone loop
masterMixer.SetFloat("masterVolume", -80f);
_spectrum = new float[AudioAnalyzer.QSamples];
_fSample = AudioSettings.outputSampleRate;
audioPlayer.clip = Microphone.Start("", true, 10, 44100);
audioPlayer.loop = true;
while(!(Microphone.GetPosition("") > 0)) { }
audioPlayer.Play();
}
void Update()
{
//Calculate frequency of currently detected tones
audioPlayer.GetSpectrumData(_spectrum, 0, FFTWindow.BlackmanHarris);
float pitchVal = AudioAnalyzer.calculateFrequency(ref _spectrum, _fSample);
if(pitchVal != 0)
{
if (pitchVal < PlayerPrefs.GetFloat("lowestFrequency"))
pitchVal = PlayerPrefs.GetFloat("lowestFrequency");
else if (pitchVal < PlayerPrefs.GetFloat("highestFrequency"))
pitchVal = PlayerPrefs.GetFloat("highestFrequency");
//This is how I'd like to call the function
//But if someone could change this and make the sprite actually
//"move" to that point instead of just popping there it would be awesome!
transform.position = new Vector2(0, FrequencyToY(pitchVal));
}
}
//Converts frequency to position on Y-axis
public float FrequencyToY(float frequency)
{
float x = 0;
return x;
}
}
You need to define the range of your Y coordinates that you want to use (say, 0 -> 100) and then scale the pitch you're given against their scale (so what % on 0 - 100 of their scale) and then use that % as a point on Y.
Thus, if they give you a note that's exactly in the middle of their scale (50%) and your Y coordinates in game range from 0-10, you want to put them at 5.
I'm trying to get the corners of the following shape:
By corners I mean this (red dots):
The minimum quantity of points that can define this shape.
And I have implemented the following:
public Shape Optimize()
{
// If the vertices are null or empty this can't be executed
if (vertices.IsNullOrEmpty())
return this; // In this case, return the same instance.
if (!edges.IsNullOrEmpty())
edges = null; //Reset edges, because a recalculation was requested
// The corners available on each iteration
var corners = new Point[] { Point.upperLeft, Point.upperRight, Point.downLeft, Point.downRight };
//The idea is to know if any of the following or previous vertice is inside of the the array from upside, if it is true then we can add it.
Point[] vs = vertices.ToArray();
for (int i = 0; i < vertices.Count - 1; ++i)
{
Point backPos = i > 0 ? vs[i - 1] : vs[vertices.Count - 1],
curPos = vs[i], //Punto actual
nextPos = i < vertices.Count - 1 ? vs[i + 1] : vs[0];
// We get the difference point between the actual point and the back & next point
Point backDiff = backPos - curPos,
nextDiff = nextPos - curPos,
totalDiff = nextPos - backPos;
if (corners.Contains(backDiff) || corners.Contains(nextDiff) || corners.Contains(totalDiff))
AddEdge(curPos, center); // If any of the two points are defined in the corners of the point of before or after it means that the actual vertice is a edge/corner
}
return this;
}
This works rectangled shapes, but rotated shapes are very sharp, so, this code doesn't work well:
Blue pixels (in this photo and the following) are the vertices variable processed on Optimize method.
Green pixels are the detected corners/edges (on both photos).
But sharpness in a shape only defines the side inclination, so what can I do to improve this?
Also, I have tested Accord.NET BaseCornersDetector inherited classes, but the best result is obtained with HarrisCornersDetector, but:
Many edges/corners are innecesary, and they aren't in the needed place (see first photo).
Well, after hours of research I found a library called Simplify.NET that internally runs the Ramer–Douglas–Peucker algorithm.
Also, you maybe interested on the Bresenham algorithm, with this algorithm you can draw a line using two Points.
With this algorithm, you can check if your tolerance is too high, comparing the actual points and the points that this algorithm outputs and making some kind of percentage calculator of similarity.
Finally, is interesting to mention Concave Hull and Convex Hull algorithms.
All this is related to Unity3D.
My outputs:
And my implementation.
It's very important to say, that points needs to be sorted forcing them to be connected. If the shape is concave as you can see on the second photo maybe you need to iterate walls of the shape.
You can see an example of implementation here. Thanks to #Bunny83.
I'm trying to create a simple mouse emulator controlled by a joystick's right thumbstick. I was trying to have the mouse move in the direction the stick pointed with a smooth gradient of pressure values dictating speed, but I've hit a number of snags when trying to do so.
The first is how to accurately translate the angle into accurate X and Y values. I can't find a way to implement the angle correctly. The way I have it, the diagonals are likely to move considerably faster than the cardinals.
I was thinking I need something like Math.Cos(angle) for the X values, and Math.Sin(angle) for the Y values to increment the mouse, but I can't think of a way to set it up.
The second, is smooth movement of the mouse, and this is probably the more important of the two. Since the SetPosition() function only works with integers, the rate at which pixels move over time seems very limited. The code I have is very basic, and only registers whole number values of 1-10. That not only creates small 'jumps' in acceleration, but limits diagonal movement as well.
The goal would to have something like 10 pixels-per-second, with the program running at 100hz, and each cycle outputting 0.1 pixel movement.
I'd imagine I might be able to keep track of the pixel 'decimals' for the X and Y values and add them to the axes when they build to whole numbers, but I'd imagine there's a more efficient way to do so and still not anger the SetPosition() function.
I feel like Vector2 objects should get this done, but I don't know how the angle would fit in.
Sample code:
//Poll Gamepad and Mouse. Update all variables.
public void updateData(){
padOne = GamePad.GetState(PlayerIndex.One, GamePadDeadZone.None);
mouse = Mouse.GetState();
currentStickRX = padOne.ThumbSticks.Right.X;
currentStickRY = padOne.ThumbSticks.Right.Y;
currentMouseX = mouse.X;
currentMouseY = mouse.Y;
angle = Math.Atan2(currentStickRY, currentStickRX);
vectorX = (int)( currentStickRX*10 );
vectorY = (int)( -currentStickRY*10 );
mouseMoveVector.X = vectorX;
mouseMoveVector.Y = vectorY;
magnitude = Math.Sqrt( Math.Pow( (currentStickRX - 0), 2 ) + Math.Pow( (currentStickRY - 0), 2 ) );
if (magnitude > 1){
magnitude = 1;
}
//Get values not in deadzone range and re-scale them from 0-1
if(magnitude >= deadZone){
activeRange = (magnitude - deadZone)/(1 - deadZone);
}
Console.WriteLine(); //Test Code
}
//Move mouse in in direction at specific rate.
public void moveMouse(){
if (magnitude > deadZone){
Mouse.SetPosition( (currentMouseX + vectorX), (currentMouseY + vectorY));
}
previousStickRX = currentStickRX;
previousStickRY = currentStickRY;
previousActiveRange = activeRange;
}
Note: I'm using all the xna frameworks.
Anyway, apologies if I'm explaining these things incorrectly. I haven't been able to find a good resource for this, and the vector examples I searched only move in integer increments and from point A to B.
Any help with any part of this is greatly appreciated.
I haven't tried it myself but from my point of view, you should normalize the pad axis after reading them, that way diagonals would move the same speed as cardinals. And for the second part, I would keep track of the mouse in floating variables, such as a Vector2 and do the cast (maybe rounding better) when setting the mouse position.
public void Start()
{
mousePosV2 = Mouse.GetState().Position.ToVector2();
}
public void Update(float dt)
{
Vector2 stickMovement = padOne.ThumbSticks.Right;
stickMovement.Normalize();
mousePosV2 += stickMovement*dt*desiredMouseSpeed;
/// clamp here values of mousePosV2 according to Screen Size
/// ...
Point roundedPos = new Point(Math.Round(mousePosV2.X), Math.Round(mousePosV2.Y));
Mouse.SetPosition(roundedPos.X, roundedPos.Y);
}
I'm working on an isometric game (diamond grid) and I've stumbled across a minor problem regarding a character movement.
I'm using A* to find a path between 2 points and then I want to move my character from point A to point B going through all the tiles which form the path but I can't find a way to do this , I mean a simpler and accurate method.
So far I've scrapped this piece of code but it's kinda "rusty"
public void Destination(tile destination)
{
for (int i = 0; i < 8; i++)
{
if (AdjacentTile[i] == destination)
{
characterDirection = i;
}
}
animation.changeSpriteDirection(characterDirection); //After I found which adjacent tile is the next destination I change the character direction based on it's position (1 = North , 2 = Nort Est etc) .. so the Y of the Animation_sourceRectangle it's changed//
Vector2 Position;
Position.X = current_characterTile.X - destination.X;
Position.Y = current_characterTile.Y - destination.Y;
rotation = (float)Math.Atan2(-Position.X, Position.Y);
moveVector = (Vector2.Transform(new Vector2(0, -1), Matrix.CreateRotationZ(rotation))) * characterSpeed;
movingCommand = 1; // the character is supposed to be moving..
Move(); //this function moves the sprite until the *tile.i and tile.j* of the character is the same as tile.j and tile.i of the destination
//something like this
if ( characterTile.i == destination.i && characterTile.j == destination.j)
movingCommand = 0 //stop
else
character_Position += moveVector;
}
If anyone could give me a hint on what to do or help me I'll be very grateful.
Thank You.
Possibilities:
At each tile, determine the character's speed vector and also determine how much time it will take for the character to move to next tile. When that time elapses, immediately begin moving to the next tile. (This is what I implemented below.)
At each tile, determine the character's speed vector. Then, when the character is sufficiently close to the next tile (say, the difference between their X and Y coordinates is less than 2 pixels?), snap it to the tile and begin moving to the next tile. This will causes artifacts and be in general less precise.
A solution:
Let's assume you already ran your pathfinding algorithm and found a linked list of a tiles that you must go through to arrive at target. Let's also assume those tiles cannot become blocked partway through the movement (it is simple to modify the algorithm if they can, though).
I usually do something like this to handle this problem:
Run the pathfinding algorithm, which returns a List, if a path
exists.
character.Path = theListThatAStarReturned;
character.beginMovingToTarget(character.Path[0]);
character.Path.RemoveAt(0);
The beginMovingToTarget() method will determine the velocity vector and also determine the the time needed to arrive at the tile. When the time is reached, we immediately go to the next tile, until the Path is empty. Let's call this time variable character.timeToArrival.
Update():
if (!character.Moving) return; // Or just don't execute the rest of this code.
character.position += character.speed * elapsedSeconds;
character.timeToArrival -= elapsedSeconds;
// Did the character arrive in a tile?
if (character.timeToArrival <= 0)
{
// This will ensure the character is precisely in the tile, not a few pixels veered off.
character.position = character.movingToTile.position;
if (character.Path.Count == 0)
{
character.Moving = false;
// We are at final destination.
}
else
{
character.beginMovingToTarget(character.Path[0]);
character.Path.RemoveAt(0);
}
}
And the beginMovingToTarget(targetTile) function:
this.movingToTile = targetTile;
Vector2 direction;
direction = targetTile.position - this.position;
this.timeToArrival = direction.Length() / this.speedPerSeconds;
direction.Normalize();
direction *= this.speedPerSeconds;
this.speed = direction;
// Here, you may also want to change the character's animation, if you want to, or you may do that directly in the Draw() method based on its speed vector.
Make sure the division is in floats, not integers.
I'm been developing my own physics engine for a school project and recently I encountered a problem: Per pixel collisions on big sprites make my FPS drop A LOT.
Here's my pixel collision code. Before entering the following code I'm using Intersects() to see if their bounding boxes collided.
private bool PerPixelCollision(IObject a, IObject b)
{
Color[] bitsA = new Color[a.Texture.Width * a.Texture.Height];
a.Texture.GetData(bitsA);
Color[] bitsB = new Color[b.Texture.Width * b.Texture.Height];
b.Texture.GetData(bitsB);
// Calculate the intersecting rectangle
int x1 = Math.Max(a.Bounds.X, b.Bounds.X);
int x2 = Math.Min(a.Bounds.X + a.Bounds.Width, b.Bounds.X + b.Bounds.Width);
int y1 = Math.Max(a.Bounds.Y, b.Bounds.Y);
int y2 = Math.Min(a.Bounds.Y + a.Bounds.Height, b.Bounds.Y + b.Bounds.Height);
Color c;
Color d;
// For each single pixel in the intersecting rectangle
for (int y = y1; y < y2; ++y)
{
for (int x = x1; x < x2; ++x)
{
// Get the color from each texture
c = bitsA[(x - a.Bounds.X) + (y - a.Bounds.Y) * a.Texture.Width];
d = bitsB[(x - b.Bounds.X) + (y - b.Bounds.Y) * b.Texture.Width];
if (c.A != 0 && d.A != 0) // If both colors are not transparent (the alpha channel is not 0), then there is a collision
{
return true;
}
}
}
// If no collision occurred by now, we're clear.
return false;
}
In the example I'm using to test I'm dropping 4 sprites in another sprite that represents the floor (736x79). When I change the sprite that represents the floor to a bigger sprite (3600x270) the FPS drops. I know the problem is in the pixel collision because I'm using a profiler.
Does anyone have any idea on how to optimize the collision?
P.S.: Sorry if I wasn't clear enough about my problem. My english is not so good.
EDIT: The first problem was solved by using the solution provided by #pinckerman but I found another one related to pixel collision detection.
When a sprite collide with a the transparent part of a texture, we get the part that intersected and check all the pixels of that part. The problem is: When the transparent part is big enough to cover the whole sprite, I check the whole texture of that sprite (currently using 50x50 textures which is 2500 pixels). Is there any way to not check the whole texture?
Thanks
I'm pretty sure that your FPS drop so much because you're doing
Color[] bitsA = new Color[a.Texture.Width * a.Texture.Height];
a.Texture.GetData(bitsA);
Color[] bitsB = new Color[b.Texture.Width * b.Texture.Height];
b.Texture.GetData(bitsB);
at the beginning of your method.
I suppose you call your PerPixelCollision every Update loop and creating and coping millions of values every game cycle it's not a very efficient thing to do.
A big sprite creates a huge Color[] array: the bigger are your arrays, the slower will be this method.
EDIT:
For your second problem, I think that, if you don't know beforehand where is the transparent area of your "big" texture, you have to check the whole sprite anyway.
If your sprite it's not too big that's not a big waste of performance.
PS: I see that you get the intersecting Rectangle on your own, maybe you could find useful this method.