Develop Reference

Unity Circle calculation

for my programm im programming a "clock like" behaviour. Meaning i
order some pictures in a circle (works)
if i click and drag on any item all items should rotate with the mouse (works)
But i get a weird bug. The first time i click and hold the mouse my images "jump" to different positions. if i hold the mouse down i can rotate my clock ust fine.
When i MouseUp and start dragin from the same image it works well. if i go to another image i get this "Jump" again.
When i only have a few images on my clock i see that it doesnt jump. but the start position seems to bee off.
When i only have one item, i can rotate it in a circle, but the moment i start to rotate it jumps away from my mouse and than i can rotate it as desired.
For me it seems to be a wrong "starting point" when first dragging an item. SInce it works fine when i than drag the same item again and again.
Unfortunately i cant find the damn bug, and im searching the whole day already.
#
public void SetLayoutHorizontal ()
{
Debug.Log ("LAYOUT");
for (var i =0; i < Rect.childCount; i++)
{
var PanelPrefab = Rect.GetChild (i) as RectTransform;
Transform ImageObject = PanelPrefab.GetComponentInChildren<Transform>().Find("Image");
if (PanelPrefab == null)
continue;
PanelPrefab.sizeDelta = CellSize;
PanelPrefab.anchoredPosition = new Vector2(radius * Mathf.Sin( CalculateCircleAngle(i) - deltaRadian),radius * Mathf.Cos(CalculateCircleAngle(i) - deltaRadian));
}
}
private float CalculateCircleAngle(int parts)
{
//parts == Number of parts the whole circle is to be cut into
return parts * (360/Rect.childCount) * (Mathf.PI/180);
}
public void OnDrag (PointerEventData eventData)
{
var diffX = eventData.position.x - _rect.rect.width/2; // MouseX - CenterScreenX
var diffY = eventData.position.y - _rect.rect.height/2; // MouseY - CenterScreenY
deltaRadian = Mathf.Atan2(diffY,diffX);
SetDirty();
}
Edit:
Ok i Edited the code but it still is not working.
I added the following method:
public void OnBeginDrag(PointerEventData eventData)
{
originalX = eventData.position.x;
originalY = eventData.position.y;
}
and i changed the drag method acordingly
public void OnDrag (PointerEventData eventData)
{
var diffX = eventData.position.x - originalX;
var diffY = eventData.position.y - originalY;
deltaRadian = Mathf.Atan2(diffY,diffX);
SetDirty();
}
The "Jumping" at the beginning of my drag event is gone, but the speed of the draggin is not on par with my mouse.
The closer i am to my starting point of the drag, the faster it moves, the further away i am the slower it gets.
I dont know if this brought me closer to a solution or further away :(
Edit2:
Ok i think the problem might be that my calculations were all done from the center point of view as 0,0 point.
Unity has the bottom left point as 0,0. So i somehow have to translate all those coordiantes first...

All that was needed was a transformation to kartesian coordinates
//Convert to kartesian coordinates with 0,0 in center of screen
var diffX = (eventData.position.x - _rect.rect.width / 2) % (_rect.rect.width / 2);
var diffY = (eventData.position.y - _rect.rect.height / 2) % (_rect.rect.height / 2);
and an addition of the delta instead of the subtraction
PanelPrefab.anchoredPosition = new Vector2(radius * Mathf.Sin(CalculateCircleAngle(i) + deltaRadian),radius * Mathf.Cos(CalculateCircleAngle(i) + deltaRadian));

Your mouse coordinates are relative to the control you click in. You could re-calculate them using the control's position within its container or you use absolute coordinates.

I don't think you are displaying all the relevant code, but your OnDrag function, specifically diffX, and diffY probably provide the answer for you.
I believe you're taking the absolute coordinates of the location you pick, and using them to generate your angle - which means that almost anywhere you click is a big jump from however the current angle is set. Your initial click handler should save off a starting coordinate, and your OnDrag should compare itself against that initial coordinate, based on how far you've dragged from that saved location.

Prevent image clipping during rotation Windows Phone

I am using the WriteableBitmapEx extension method to rotate a WriteableBitmap. bi in the code is a WritableBitmap. The RotateFree method rotates the bitmap in any degree and returns a new rotated WritableBitmap. My code:
private void rotate()
{
degree += 1;
var rotate = bi.RotateFree(degree);
ImageControl.Source = rotate;
}
My problem is since the ImageControl size is fixed, it causes the rotated bitmap to be clipped. So what is the best way to prevent this? I guess I am looking for a way to resize the ImageControl during rotation to prevent clipping. Any suggestions?
UPDATE
Based on this useful info Calculate rotated rectangle size from known bounding box coordinates I think I managed to calculate the bounding box width (bx) and height(by) and resize it accordingly during the rotation
double radian = (degree / 180.0) * Math.PI;
double bx = rotate.PixelWidth * Math.Cos(radian) + rotate.PixelHeight * Math.Sin(radian);
double by = rotate.PixelWidth * Math.Sin(radian) + rotate.PixelHeight * Math.Cos(radian);
While it appears that the ImageControl width and height increases/decreases during rotation, the image is still being clipped.
UPDATE 2
Based on #Rene suggestion, I managed to prevent the clipping. Combined with the ImageControl Width/Height calculation, the image size is retained during rotation by also setting its stretch property to NONE.
The issue now is to make sure the ImageControl resize from its center so that it does not appear moving. I can include a sample project if anyone interested
UPDATE 3
For those who might be interested the final solution. This is how I do it. The result is, the image is rotated without clipping and its size is retained during rotation. In addition, the rotation appears to originate from the center.
To adjust the ImageControl position as it's resizing so that the rotation appears to originated from center, I use this code.
var translationDelta = new Point((ImageControl.ActualWidth - bx) / 2.0, (ImageControl.ActualHeight - by) / 2.0);
UpdateImagePosition(translationDelta);
ApplyPosition();
// This code update the ImageControl position on the canvas
public void UpdateImagePosition(Point delta)
{
var newPosition = new Point(ImagePosition.X + delta.X, ImagePosition.Y + delta.Y);
ImagePosition = newPosition;
}
//This apply the new position to make the ImageControl rotate from center
public void ApplyPosition()
{
ObjComposite.TranslateX = ImagePosition.X;
ObjComposite.TranslateY = ImagePosition.Y;
}

Use RotateFree with the crop parameter set to false: RotateFree(degree, false). Also set the ImageControl Stretch property to Uniform: Stretch="Uniform".
rene

Dynamically scaling canvas in WPF by setting in- and outpoints

I'm working on plotting program in WPF using the canvas element. What I want to achieve is a scrollbar with draggable endpoints. Example of these kinds of scrollbars are in the After Effects video editing software by Adobe.
Basic functionality of such a scrollbar is that it is able to scroll trough content that is bigger then it's container, but both the left and right endpoint can be dragged to dynamically change the scale of the content.
I have implemented a similar scrollbar in the plotting program; users should be able to drag around the in and outpoint (Rectangles in a canvas), and the plot canvas should respond to this by scaling to the desired range.
Information I need for this:
Width of the total plot (amount of plotpoints)
Width of the container (static, 600px)
Percentage of the in and out points relative to the total width of the scrollbar canvas
Link to current screenshot
With this information I have created a MatrixTransform, using the ScaleAt() method to scale the plot canvas inside the container so that it matches the in and outpoints in the scrollbar below. For this I used the following code. resetTransform gets called FPS times a second to keep up with the incoming data and XMAX and YMAX are updated elsewhere to reflect this.
public void resetTransform(Boolean useSlider = false)
{
//Add transformgroup to plot
double yscale = plot.Height / view.YMAX; //YMAX is maximum plot value received
double xscale = plot.Width / view.XMAX; //XMAX is total ammount of plotted points
Matrix m = new Matrix(1, 0, 0, 1, 0, 0);
if (useSlider)
{
double maxVal = zoomBar.ActualWidth - outPoint.Width;
double outP = Canvas.GetLeft(outPoint); //points position relative to the scrollbar
double inP = Canvas.GetLeft(inPoint);
double center = (((outP + inP) / 2) / maxVal) * plot.ActualWidth;
double delta = (outP-inP);
double factor = (maxVal/delta) * xscale;
double mappedinP = (inP / maxVal) * view.XMAX;
double anchorOut = (outP / maxVal) * view.XMAX;
double anchorIn = (inP / maxVal) * view.XMAX;
m.ScaleAt(factor, -yscale,center,0); //scale around the center point,
m.Translate(0, plot.Height); //to compensate the flipped graph, move it back down
}
scale = new ScaleTransform(m.M11, m.M22, 0, 0); //save scale factors in a scaletransform for reference
signals.scaleSignalStrokes(scale); //Scale the plotlines to compensate for canvas scaling
MatrixTransform matrixTrans = new MatrixTransform(m); //Create matrixtransform
plot.RenderTransform = matrixTrans; //Apply to canvas
}
Expectation: Everything should work and the plotted graph would scale nicely when the amount of plotpoints grows over time. Reality: The graph scales when moving the points around, but it is not representative; Moreover, the more plot points are added, the more the whole canvas shifts to the right and the less control I seem to have over the transformation. The algorithm as it is now is probably to wrong approach to get the result I need, but I have spent quite some time thinking how to do this right.
Update
I have uploaded a video to give a clearer picture on the interaction. In the video you can clearly see the canvas shifting to the right.
Screencapture video
How should I scale the canvas (plot) to fit within two boundaries?

So, after some struggling, I found the right algorithm to solve this problem. I will post the adjusted version of the resetTransform function below:
//Reset graph transform
public void resetTransform(Boolean useSlider = false)
{
double yscale = plot.Height / view.YMAX; //YMAX is maximum plot value received
double xscale = plot.Width / view.XMAX; //XMAX is total ammount of plotted points
Matrix m = new Matrix(1, 0, 0, 1, 0, 0);
if (useSlider)
{
double maxVal = zoomBar.ActualWidth - outPoint.Width;
double outP = Canvas.GetLeft(outPoint); //points position relative to the scrollbar
double inP = Canvas.GetLeft(inPoint);
double delta = (outP-inP);
double factor = (maxVal/delta) * xscale;
anchorOut = (outP / maxVal) * view.XMAX; //Define anchorpoint coordinates
anchorIn = (inP / maxVal) * view.XMAX;
double center = (anchorOut +anchorIn)/2; //Define centerpoint
m.Translate(-anchorIn, 0); //Move graph to inpoint
m.ScaleAt(factor, -yscale,0,0); //scale around the inpoint, with a factor so that outpoint is plot.Height(=600px) further away
m.Translate(0, plot.Height); //to compensate the flipped graph, move it back down
}
scale = new ScaleTransform(m.M11, m.M22, 0, 0); //save scale factors in a scaletransform for reference
signals.scaleSignalStrokes(scale); //Scale the plotlines to compensate for canvas scaling
MatrixTransform matrixTrans = new MatrixTransform(m); //Create matrixtransform
plot.RenderTransform = matrixTrans; //Apply to canvas
}
So rather than scaling around the centre point, I should first translate the image and then scale around the origin of the canvas with a factor. This means the other side of the canvas is exactly plot.Height pixels away (with some added scaling)
Everything seems to work fine now, but because I am using custom controls (draggable Rectangles in a canvas) I notice these rectangles do not always fire the mousse events.
Since it is out of the scope of this question, I've described the issue further in this post

PictureBox zoom miscalculation

I am attempting to zoom in a picturebox using the mousewheel.
Using the following variables:
public static int offsetX = 0;
public static int offsetY = 0;
public static double scale = .05;
I draw a series of polygons to the picture box. However, I wanted the bottom left corner to refer to 0,, so I draw everything to the form with a -y. The drawn points have been affected by the above variables but the real points stay the same.
void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
{
if (e.Delta > 0)
scale += .025;
else
scale -= .025;
pictureBox1.Invalidate();
}
When the mousewheel is moved forward I increase the scale variable and the box is refreshed. It is repainted using this code in the picturebox paint method:
Graphics g = e.Graphics;
foreach (Member m in activeTruss.members)
{
if (m.Visible == true)
{
Point[] pointArray = new Point[m.poly.Points.Count()];
int index = 0;
foreach (System.Windows.Point p in m.poly.Points)
{
pointArray[index].X = (int)((p.X + offsetX) * scale);
pointArray[index].Y = (int)-((p.Y + offsetY) * scale);
index++;
}
SolidBrush myBrush = new SolidBrush(m.color);
g.FillPolygon(myBrush, pointArray);
}
}
it zooms the correct amount, however it appears to zoom towards the upper left corner because the offsets stay the same. The opposite is true when zooming out. How should I edit the offsets as I turn the mouse wheel in order to zoom directly towards the point under my mouse?

If you want to center your zoom
double offsetX = scale/2
double offsetY = scale/2
Update
To answer your second part about flipped picture, it sounds like you are not making a distinction on the x,y of your picture vs the x,y screen coordinates. Usually, screen coordinates start on the top of the screen, so top left is 0,0, however when you draw your picture, your picture's 0,0 is on the bottom left so you use -y. What you want to do is to start drawing from 0,0 to 0,MAXY without the flip. For this implementation detail, your code would help alot hehe :)

mouse picking a rotating sprite in an Xna game

I am working on a simple game where you click on square sprites before they disappear. I decided to get fancy and make the squares rotate. Now, when I click on the squares, they don't always respond to the click. I think that I need to rotate the click position around the center of the rectangle(square) but I am not sure how to do this. Here is my code for the mouse click:
if ((mouse.LeftButton == ButtonState.Pressed) &&
(currentSquare.Contains(mouse.X , mouse.Y )))
And here is the rotation logic:
float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
RotationAngle += elapsed;
float circle = MathHelper.Pi * 2;
RotationAngle = RotationAngle % circle;
I am new to Xna and programming in general, so any help is appreciated.
Thanks a lot,
Bill

So you're trying to determine if a point is in a rectangle, but when the rectangle is rotated?
The Contains() method will only work if the current rotation is 0 (I guess currentSquare is a rectangle representing the image position without rotation?).
What you will have to do is do the opposite rotation of the image on the mouse coordinates (the mouse coordinates should rotate around the origin of your image), then calculate if the new position is within currentSquare. You should be able to do all of this using vectors.
(Untested)
bool MouseWithinRotatedRectangle(Rectangle area, Vector2 tmp_mousePosition, float angleRotation)
{
Vector2 mousePosition = tmp_mousePosition - currentSquare.Origin;
float mouseOriginalAngle = (float)Math.Atan(mousePosition.Y / mousePosition.X);
mousePosition = new Vector2((float)(Math.Cos(-angleRotation + mouseOriginalAngle) * mousePosition.Length()),
(float)(Math.Sin(-angleRotation + mouseOriginalAngle) * , mousePosition.Length()));
return area.Contains(mousePosition);
}

If you dont need pixel pefect detection you can create bounding sphere for each piece like this.
var PieceSphere = new BoundingSphere()
{
Center =new Vector3(new Vector2(Position.X + Width/2, Position.Y + Height/2), 0f),
Radius = Width / 2
};
Then create another bounding sphere around mouse pointer.For position use mouse coordinates and for radius 1f. Because mouse pointer will be moving it will change its coordinates so you have to also update the sphere's center on each update.
Checking for clicks would be realy simple then.
foreach( Piece p in AllPieces )
{
if ((mouse.LeftButton == ButtonState.Pressed) && p.BoundingSphere.Intersects(MouseBoundingSphere))
{
//Do stuff
}
}

If you are lazy like me you could just do a circular distance check.
Assuming mouse and box.center are Vector2
#gets us C^2 according to the pythagorean Theorem
var radius = (box.width / 2).squared() + (box.height / 2).square
#distance check
(mouse - box.center).LengthSquared() < radius
Not perfectly accurate but the user would have a hard time noticing and inaccuracies that leave a hitbox slightly too large are always forgiven. Not to mention the check is incredibly fast just calculate the radius when the square is created.