I'm trying to add direction arrows to a MKPolyline, and I've almost got it, but for some reason some of the arrows are chopped off (see screen shot below). I'm not great at drawing with Core Graphics, so my guess is it's something in there. Anyone have any pointers on how to deal with the clipped arrows?
The following code does the drawing from in the drawMapRect:zoomScale:inContext: method of a subclassed MKPolylineRenderer:
MKMapPoint prevMapPoint = mapPoints[0];
MKMapPoint mapPoint = mapPoints[1];
for (NSUInteger i = 1; i < pointCount; i++) {
mapPoint = _mapPoints[i];
CGPoint prevCGPt = [self pointForMapPoint:prevMapPoint];
CGPoint cgPoint = [self pointForMapPoint:mapPoint];
CGFloat bearing = atan2(cgPoint.y - prevCGPt.y, cgPoint.x - prevCGPt.x) - M_PI;
//Get other two corners of triangle
CGFloat arrowAngle = degreesToRadians(40.0);
CGPoint pt2 = PointAtBearingFromPoint(cgPoint, bearing+arrowAngle/2, arrowLength);
CGPoint pt3 = PointAtBearingFromPoint(cgPoint, bearing-arrowAngle/2, arrowLength);
//Draw triangle and fill
CGContextBeginPath(context);
CGContextMoveToPoint(context, cgPoint.x, cgPoint.y); //go to tip of triangle
CGContextAddLineToPoint(context, pt2.x, pt2.y);
CGContextAddLineToPoint(context, pt3.x, pt3.y);
CGContextClosePath(context);
CGContextFillPath(context);
}
prevMapPoint = mapPoint;
(also in the drawMapRect:zoomScale:inContext: method is a For loop to decide where to put each arrow and populate the mapPoints array, but I'm assuming that isn't the problem).
Related
I have created a class where I define Shape objects for my program. Each of these Shapes has a transparent ellipse drawn around it (I defined that in my constructor) and if any other Shape moves into that circular ellipse area, I want that Shape to change it's direction so that it moves in a circular path.
Each Shape object has a defined radius attribute (because of the ellipse I draw around each object) and I want to use that value to determine how big of a circular pattern the Shape has to move in when it collides.
Please help! Anything is greatly appreciated!
EDIT:
As I said above, I want the shape to move into a circular path. HOWEVER, I want it only to move in a circular path once (meaning it moves around a circle once) and then I want it to continue on the original path it was programmed with.
The short answer is that you'll have to use basic trig to figure out the angle between the points, and then more basic trig to determine subsequent points on the circular path.
Check out the trigonometry section of the Processing reference for more info.
But basically, if you have two points, you can use the atan2() function to calculate the angle between them. You'd use this to find the starting angle from the center of your circle to the shape.
Once you have that angle, you can simply increment it, and then use cos() and sin() to figure out the x and y coordinates at that new angle.
Here is a basic sketch that does all of the above:
PVector center;
float angle;
float radius;
void setup() {
size(500, 500);
center = new PVector(width/2, height/2);
//get the initial point
//for you, this would be the initial location of the object
PVector point = new PVector(random(width), random(height));
//find the angle between the points
float deltaX = center.x - point.x;
float deltaY = center.y - point.y;
angle = atan2(deltaX, deltaY);
//find the radius of the circle
radius = dist(center.x, center.y, point.x, point.y);
ellipseMode(RADIUS);
}
void draw() {
background(0);
//draw the center point
ellipse(center.x, center.y, 10, 10);
//find the point based on the angle
float x = center.x + cos(angle)*radius;
float y = center.y + sin(angle)*radius;
//draw the traveling point
ellipse(x, y, 10, 10);
//increment the angle to move the point
angle += PI/120;
}
Well, before I saw Kevin's post, I did one also. Not using objects, just a simple procedural example. Posting anyway :)
PVector pos, speed, stored;
float diam = 40;
boolean wonder = false;
float angle = 0;
void setup() {
size(300, 300);
// arbitrary positioning and speeding
pos = new PVector(-20, height/2);
speed = new PVector(1, 0);
noStroke();
}
void draw() {
background(5);
// normally increment speed
if (!wonder) {
pos.add(speed);
} else {
// if is to wonder...
if (angle <= 360) {
//get circle path by trig
pos.x = stored.x + cos(radians(angle))*diam;
pos.y = stored.y + sin(radians(angle))*diam;
} else {
// if the circle is complete
// reset angle and stop wondering
wonder = false;
angle = 0;
}
// increment angle
angle++;
}
// draw
ellipse(pos.x, pos.y, diam, diam);
}
void mouseClicked() {
if (isOverCircle() ) {
// store position where it has being clicked
stored = pos.get();
// off set the diam
stored.x -= diam;
// trig wondering
wonder = true;
angle = 0;
}
}
boolean isOverCircle() {
float disX = pos.x - mouseX;
float disY = pos.y - mouseY;
return sqrt(sq(disX) + sq(disY)) < diam/2;
}
UPDATE
I need to draw a circle onto a MKMapView, something where I can get the radius of the circle and it's center coordinate. However, I would also like the circle to be a subview of the MKMapView, so that the map view can scroll underneath the circle, updating its center coordinate as the map moves and updating its radius as the map is zoomed in and out.
Does anyone know how I might be able to accomplish this?
This is the original wording of the question
I've drawn a circle onto a MKMapView using the code below:
- (void)viewDidLoad
{
[super viewDidLoad];
self.locationManager = [[CLLocationManager alloc] init];
self.locationManager.delegate = self;
self.region = [MKCircle circleWithCenterCoordinate:self.locationManager.location.coordinate radius:kViewRegionDefaultDistance];
[self.mapView addOverlay:self.region];
}
- (MKOverlayPathRenderer *)mapView:(MKMapView *)map viewForOverlay:(id <MKOverlay>)overlay
{
MKCircleRenderer *region = [[MKCircleRenderer alloc] initWithOverlay:overlay];
region.strokeColor = [UIColor blueColor];
region.fillColor = [[UIColor blueColor] colorWithAlphaComponent:0.4];
return region;
}
This works and produces a circle on the map view. However, when I scroll the map view, the circle moves with it. I would like the circle to remain stationary and have the map view scroll underneath the circle.
Is is important to note that I will need to get the center coordinate and radius of the circle in order to create a region. For that reason, I cannot simply draw a UIView on top of the MKMapView, as I would have no way to get the radius in meters of the UIView.
I solved it!
Step 1:
I created a UIView and added it as a subview to the map view. It is important to note that I made sure to center the UIView on the map view. This is important because you will use the centerCoordinate property of the MKMapView to calculate the radius.
self.region = [[UIView alloc] initWithFrame:centerOfMapViewFrame];
self.region.contentMode = UIViewContentModeRedraw;
self.region.userInteractionEnabled = NO;
self.region.alpha = 0.5;
self.region.layer.cornerRadius = widthOfView/2;
self.region.backgroundColor = [UIColor blueColor];
[self.mapView addSubview:self.region];
The image below shows the circular UIView added as a subview to the mapView.
Step 2:
Calculate the radius based off of the center coordinate of map view and the edge coordinate of the UIView.
CLLocationCoordinate2D edgeCoordinate = [self.mapView convertPoint:CGPointMake((CGRectGetWidth(self.region.bounds)/2), 0) toCoordinateFromView:self.region]; //self.region is the circular UIView
CLLocation *edgeLocation = [[CLLocation alloc] initWithLatitude:edgeCoordinate.latitude longitude:edgeCoordinate.longitude];
CLLocation *centerLocation = [[CLLocation alloc] initWithLatitude:self.mapView.centerCoordinate.latitude longitude:self.mapView.centerCoordinate.longitude];
CGFloat radius = [edgeLocation distanceFromLocation:centerLocation]; //is in meters
The image below shows an annotation on the edgeLocation and on the centerLocation.
Swift 4.2/5 adaptation
let edgeCoordinate = self.mapView.convert(mapView.center, toCoordinateFrom: overlayView)
let edgeLocation: CLLocation = .init(latitude: edgeCoordinate.latitude, longitude: edgeCoordinate.longitude)
let centerLocation: CLLocation = .init(latitude: mapView.centerCoordinate.latitude, longitude: mapView.centerCoordinate.longitude)
let radius = edgeLocation.distance(from: centerLocation)
// do something with the radius
Where overlayView is the custom circle you created to represent radius
Why is my SKPhysicsBody positioned way off from the SKSpriteNode that it is attached to? This is how I create the physics body:
self.pin = [SKSpriteNode spriteNodeWithImageNamed:[IPGameManager sharedGameData].world.player.ship.type];
self.pin.position = CGPointMake([IPGameManager sharedGameData].world.player.location.xCoordinate, [IPGameManager sharedGameData].world.player.location.yCoordinate);
self.pin.userInteractionEnabled = NO;
NSLog(#"Pin width: %f", self.pin.size.width);
NSLog(#"Pin position: %f %f", self.pin.position.x, self.pin.position.y);
self.pin.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:self.pin.size.width * 0.5 center:self.pin.position];
self.pin.physicsBody.dynamic = YES;
self.pin.physicsBody.allowsRotation = NO;
self.pin.physicsBody.friction = 0.0;
self.pin.physicsBody.linearDamping = 0.0;
By setting skView.showsPhysics = YES;, it shows the physics bodies and the circle is WAY off the SKSpriteNode. Any idea why?
You are setting the center position of the physicsBody to the be the CGPoint value of self.pin.position, which is a point in self.pin's parent node's coordinate space. If you are looking to have the physics body simply be centered in self.pin, then you would either use a 0,0 position for center (or not use the method with center at all), or an offset point if you have moved the anchor position of self.pin:
[SKPhysicsBody bodyWithCircleOfRadius:self.pin.size.width * 0.5 center:CGPointZero];
//OR
[SKPhysicsBody bodyWithCircleOfRadius:self.pin.size.width * 0.5 ]
I need a radial gradient in the shape of an oval or ellipse and it seems like it CGContextDrawRadialGradient can only draw a perfect circle. I've been drawing to a square context then copying/drawing into a rectangular context.
Any better way to do this?
Thanks!
The only way I've found to do this is as Mark F suggested, but I think the answer needs an example to be easier to understand.
Draw an elliptical gradient in a view in iOS (and using ARC):
- (void)drawRect:(CGRect)rect {
CGContextRef ctx = UIGraphicsGetCurrentContext();
// Create gradient
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = {0.0, 1.0};
UIColor *centerColor = [UIColor orangeColor];
UIColor *edgeColor = [UIColor purpleColor];
NSArray *colors = [NSArray arrayWithObjects:(__bridge id)centerColor.CGColor, (__bridge id)edgeColor.CGColor, nil];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)colors, locations);
// Scaling transformation and keeping track of the inverse
CGAffineTransform scaleT = CGAffineTransformMakeScale(2, 1.0);
CGAffineTransform invScaleT = CGAffineTransformInvert(scaleT);
// Extract the Sx and Sy elements from the inverse matrix
// (See the Quartz documentation for the math behind the matrices)
CGPoint invS = CGPointMake(invScaleT.a, invScaleT.d);
// Transform center and radius of gradient with the inverse
CGPoint center = CGPointMake((self.bounds.size.width / 2) * invS.x, (self.bounds.size.height / 2) * invS.y);
CGFloat radius = (self.bounds.size.width / 2) * invS.x;
// Draw the gradient with the scale transform on the context
CGContextScaleCTM(ctx, scaleT.a, scaleT.d);
CGContextDrawRadialGradient(ctx, gradient, center, 0, center, radius, kCGGradientDrawsBeforeStartLocation);
// Reset the context
CGContextScaleCTM(ctx, invS.x, invS.y);
// Continue to draw whatever else ...
// Clean up the memory used by Quartz
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
Put in a view with a black background you get:
You can change the transform of the context to draw an ellipse (for example, apply CGContextScaleCTM(context, 2.0, 1.0) just before calling CGContextDrawRadialGradient () to draw an elliptical gradient that's twice as wide as it is high). Just remember to apply the inverse transform to your start and end points, though.
XNA doesn't have any methods which support circle drawing.
Normally when I had to draw circle, always with the same color, I just made image with that circle and then I could display it as a sprite.
But now the color of the circle is specified during runtime, any ideas how to deal with that?
You can simply make an image of a circle with a Transparent background and the coloured part of the circle as White. Then, when it comes to drawing the circles in the Draw() method, select the tint as what you want it to be:
Texture2D circle = CreateCircle(100);
// Change Color.Red to the colour you want
spriteBatch.Draw(circle, new Vector2(30, 30), Color.Red);
Just for fun, here is the CreateCircle method:
public Texture2D CreateCircle(int radius)
{
int outerRadius = radius*2 + 2; // So circle doesn't go out of bounds
Texture2D texture = new Texture2D(GraphicsDevice, outerRadius, outerRadius);
Color[] data = new Color[outerRadius * outerRadius];
// Colour the entire texture transparent first.
for (int i = 0; i < data.Length; i++)
data[i] = Color.TransparentWhite;
// Work out the minimum step necessary using trigonometry + sine approximation.
double angleStep = 1f/radius;
for (double angle = 0; angle < Math.PI*2; angle += angleStep)
{
// Use the parametric definition of a circle: http://en.wikipedia.org/wiki/Circle#Cartesian_coordinates
int x = (int)Math.Round(radius + radius * Math.Cos(angle));
int y = (int)Math.Round(radius + radius * Math.Sin(angle));
data[y * outerRadius + x + 1] = Color.White;
}
texture.SetData(data);
return texture;
}