It's been a while, as I was hospitalized for 3 months after a motorcycle accident.
So I just got to renew my apple programming subscription :-)
I have another question that has been on my mind for quite some time.
In my iPad application I draw a triangle in the center of an iPad like this:
- (void)initTriangle
{
CGRect screenBound = [[UIScreen mainScreen] bounds];
CGSize screenSize = screenBound.size;
CGFloat screenWidth = screenSize.width;
CGFloat screenHeight = screenSize.height;
// draw triangle (TRIANGLE)
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path,NULL, 0.5*screenWidth, 0.5*screenHeight-25);
CGPathAddLineToPoint(path, NULL, 0.5*screenWidth-25, 0.5*screenHeight+25);
CGPathAddLineToPoint(path, NULL, 0.5*screenWidth+25, 0.5*screenHeight+25);
CGPathAddLineToPoint(path, NULL, 0.5*screenWidth, 0.5*screenHeight-25);
CAShapeLayer *triangle = [CAShapeLayer layer];
[triangle setPath:path];
[triangle setFillColor:[[UIColor blackColor] CGColor]];
[[[self view] layer] addSublayer:triangle];
CGPathRelease(path);
}
And I call this from my viewDidLoad like this:
[self initTriangle];
Now I'm trying to rotate this triangle with the rotation of my iPad around Z-Axis while laying flat on the table. I have a function that gives me the yaw readings in float and I'm calling my
-(void)updateTriangleWithYaw:(float)yaw
method, but I don't know what to exactly put in there to make it rotate.
here is what my method looks like so far:
-(void)updateTriangleWithYaw:(float)yaw
{
CGRect screenBound = [[UIScreen mainScreen] bounds];
CGSize screenSize = screenBound.size;
CGFloat screenWidth = screenSize.width;
CGFloat screenHeight = screenSize.height;
NSLog(#"YAW: %f", yaw);
Z += 2 * yaw;
Z *= 0.8;
CGFloat newR = R + 10 * yaw;
self.triangle.frame = CGRectMake(0.5*screenWidth, 0.5*screenHeight, newR, newR);
}
Any help will be greatly appreciated!
Thanks and be safe guys!!
You should set the layer's affineTransform. You can apply a rotation transform like:
[self.triangle setAffineTransform:CGAffineTransformMakeRotation(yaw)];
This method, setAffineTransform is a convenience to set the transform property of the layer, which is a more general type of transform CATransform3D. You can also set the transform of the layer directly, and if you want to do that you can make a rotation about the z-axis like:
self.triangle.transform = CATransform3DMakeRotation(yaw, 0, 0, 1);
In this case the first argument is the angle (in radians) and the last three arguments specify the axis of rotation.
Note that you should not assign or depend on the value of the frame property of a layer whose transform is not the identity (CGAffineTransformIdentity). When you use the transform property you should set the size and position of your layer by assigning the layer's center and bounds properties, and similarly you should read the center and bounds when you want to find out information about the layer's position and size.
I'm having some trouble achieving the result I need.
Using the method visibleRect of UIScrollView, and using the gesture recognizer, I can get where, in the screen, the user touched, or draw a rect, for example.
Where I'm having some trouble is getting the information of where that touch event is relative to the document shown in the UIScrollView.
So, if I have a document like A4 size or Letter size, and the visible part is the bottom of that document, using the above method I can see the user tapped the top content of the window. But how can I know what that point refers to the document shown?
Use contentOffset to achieve that:
Add scroll offest to x and y touches:
CGFloat xOffset = _myScrollView.contentOffset.x;
CGFloat yOffset = _myScrollView.contentOffset.y;
Then take of it the position of the scrollview:
CGRect frame = _myScrollView.frame;
All:
CGFloat pdfTouchX = screenTouchX - frame.origin.x + xOffset;
CGFloat pdfTouchY = screenTouchY - frame.origin.y + yOffset;
Can I change the color of NSTableView's border. The gray line at the pointer.
Thanks.
You need to SubClass your NSScrollView . NSScrollView doesn't usually do any drawing, and probably has a weird interaction with its child views in that way. I'd suggest putting something like
- (void)drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
// We're going to be modifying the state for this,
// so allow it to be restored later
[NSGraphicsContext saveGraphicsState];
// Choose the correct color; isFirstResponder is a custom
// ivar set in becomeFirstResponder and resignFirstResponder
[[NSColor redColor]set];
// Create two rects, one slightly outset from the bounds,
// one slightly inset
NSRect bounds = [self bounds];
NSRect innerRect = NSInsetRect(bounds, 2, 2);
NSRect outerRect = NSMakeRect(bounds.origin.x - 2,
bounds.origin.y - 2,
bounds.size.width + 4,
bounds.size.height + 4);
// Create a bezier path using those two rects; this will
// become the clipping path of the context
NSBezierPath * clipPath = [NSBezierPath bezierPathWithRect:outerRect];
[clipPath appendBezierPath:[NSBezierPath bezierPathWithRect:innerRect]];
// Change the current clipping path of the context to
// the enclosed area of clipPath; "enclosed" defined by
// winding rule. Drawing will be restricted to this area.
// N.B. that the winding rule makes the order that the
// rects were added to the path important.
[clipPath setWindingRule:NSEvenOddWindingRule];
[clipPath setClip];
// Fill the rect; drawing is clipped and the inner rect
// is not drawn in
[[NSBezierPath bezierPathWithRect:outerRect] fill];
[NSGraphicsContext restoreGraphicsState];
}
Easy way to set border to scrollview
let scrollView = NSScrollView()
scrollView.contentView.wantsLayer = true
scrollView.contentView.layer?.borderColor = NSColor.black
scrollView.contentView.layer?.cornerRadius = 6
I need to draw lots of polygons 500k to a million on the iPad. After experimenting, I can only get only get 1 fps if that. This is just an example my real code has some good sized polygons.
Here are a few question:
Why don't I have to add the Quartz Framework to my project?
If many of the polygons repeat can I leverage that with views or are they too heavy etc?
Any alternatives, QTPaint can handle this but dips into the gpu. Is there is anything like QT or ios?
Can Opengl increase 2d performance of this type?
Example drawrect:
//X Y Array of boxes
- (void)drawRect:(CGRect)rect
{
int reset = [self pan].x;
int markX = reset;
int markY = [self pan].y;
CGContextRef context = UIGraphicsGetCurrentContext();
for(int i = 0; i < 1000; i++)//1,000,000
{
for(int j = 0; j < 1000; j++)
{
CGContextMoveToPoint(context, markX, markY);
CGContextAddLineToPoint(context, markX, markY + 10);
CGContextAddLineToPoint(context, markX + 10, markY + 10);
CGContextAddLineToPoint(context, markX + 10, markY);
CGContextAddLineToPoint(context, markX, markY);
CGContextStrokePath(context);
markX+=12;
}
markY += 12;
markX = reset;
}
}
The pan just move the array of boxes around on screen with pan gesture. Any help or hints would greatly appreciated.
The key issue with your example is that it is not optimized. Whenever drawRect: is called, the device is rendering all 1,000,000 squares. Worse still, it's making 6,000,000 calls to those APIs in the loop. If you want to refresh this view at even a modest 30fps, that is 180,000,000 calls / second.
With your 'simple' example, the size of the draw area is 12,000px × 12,000px; the maximum area you can display on the iPad's display is 768×1024 (assuming full-screen portrait). Therefore, the code is wasting a lot of CPU resources drawing outside the visible area. UIKit has ways of handling this scenario with relative ease.
When managing content that is significantly larger than the visible area, you should limit drawing to only that which is visible. UIKit has a couple of ways of handing this; UIScrollView in combination with a view backed by a CATiledLayer is your best bet.
Steps:
Disclaimer: This is specifically an optimization of your example code above
Create a new View Based Application iPad project
Add a reference to the QuartzCore.framework
Create a new class, say MyLargeView, subclassed from UIView and add the following code:
:
#import <QuartzCore/QuartzCore.h>
#implementation MyLargeView
- (void)awakeFromNib {
CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
tiledLayer.tileSize = CGSizeMake(512.0f, 512.0f);
}
// Set the layer's class to be CATiledLayer.
+ (Class)layerClass {
return [CATiledLayer class];
}
- (void)drawRect:(CGRect)rect {
// Drawing code
// only draws what is specified by the rect parameter
CGContextRef context = UIGraphicsGetCurrentContext();
// set up some constants for the objects being drawn
const CGFloat width = 10.0f; // width of rect
const CGFloat height = 10.0f; // height of rect
const CGFloat xSpace = 4.0f; // space between cells (horizontal)
const CGFloat ySpace = 4.0f; // space between cells (vertical)
const CGFloat tWidth = width + xSpace; // total width of cell
const CGFloat tHeight = height + ySpace;// total height of cell
CGFloat xStart = floorf(rect.origin.x / tWidth); // first visible cell (column)
CGFloat yStart = floorf(rect.origin.y / tHeight); // first visible cell (row)
CGFloat xCells = rect.size.width / tWidth + 1; // number of horizontal visible cells
CGFloat yCells = rect.size.height / tHeight + 1; // number of vertical visible cells
for(int x = xStart; x < (xStart + xCells); x++) {
for(int y = yStart; y < (yStart + yCells); y++) {
CGFloat xpos = x*tWidth;
CGFloat ypos = y*tHeight;
CGContextMoveToPoint(context, xpos, ypos);
CGContextAddLineToPoint(context, xpos, ypos + height);
CGContextAddLineToPoint(context, xpos + width, ypos + height);
CGContextAddLineToPoint(context, xpos + width, ypos);
CGContextAddLineToPoint(context, xpos, ypos);
CGContextStrokePath(context);
}
}
}
#end
Edit the view controller nib and add a UIScrollView to the view
Add a UIView to the UIScrollView and make sure it fills the UIScrollView
Change the class to MyLargeView
Set frame size of MyLargeView to 12,000×12,000
Finally, open up the view controller .m file and add the following override:
:
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
[super viewDidLoad];
UIScrollView *scrollView = [self.view.subviews objectAtIndex:0];
scrollView.contentSize = CGSizeMake(12000, 12000);
}
If you look at the drawRect: call, it is only drawing into the area specified by the rect parameter, which will correspond to the tile size (512×512) for the CATiledLayer we configured in the awakeFromNib method. This will scale to a 1,000,000×1,000,000 pixel canvas.
Alternatives to look at are the ScrollViewSuite example, specifically 3_Tiling.
OpenGL is GPU hardware accelerated on iOS devices. Core Graphics drawing is not, and can be many many times slower when dealing with a large number of small graphics primitives (lines).
For lots of small squares, just writing them into a bitmap in C code is faster than Core Graphics line drawing. Then just draw the bitmap to the view once when done. But Open GL would be even faster.
point 4. OpenGL should do that fine. Check if you could reuse those objects and whether you could move some of the logic to GLSL code.
OpenGL performance optimization (in context of WebGL but most of it should apply): http://www.youtube.com/watch?v=rfQ8rKGTVlg
I don't know the details of iOS history so this may not have been an option when the question was first posted. However, I wanted to call out CAShapeLayer as a simple option when dealing with path performance problems. "iOS Core Animation: Advanced Techniques" (find it on Google Books) says CAShapeLayer "uses hardware-accelerated drawing" which I'm taking to mean that it's a GPU-based implementation. The same book has a good usage example in chapter 6, which boils down to this:
Create a CAShapeLayer
Configure its lineWidth, fillColor, strokeColor, etc.
Add the layer as a sublayer of your view's containerView.layer
To draw a path, just set it to the layer's "path" property
This made a gigantic performance difference in my app, as measured by Instruments. If your performance problem is path-based, don't wade into OpenGL before you've tried CAShapeLayer.
I encountered the same problem. After endless searching on google,CAShapeLayer saved me finally! Here is the detail steps you need to do:
Create a view with CAShapeLayer as it's layer type by override UIView's + (Class)layerClass method
Configure the layer's lineWidth, fillColor, strokeColor, etc.
Create an UIBezierPath instance
To draw a path,use UIBezierPath instance to add lines,curve,or acr etc, after you finished drawing, just set bezierPath.CGPath to the
layer's "path" property
Here is a simple demo to draw a simple curve when you touch the demo view:
//Simple ShapelayerView.m
-(instancetype)init {
self = [super init];
if (self) {
_bezierPath = [UIBezierPath bezierPath];
CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
shapeLayer.lineWidth = 5;
shapeLayer.lineJoin = kCALineJoinRound;
shapeLayer.lineCap = kCALineCapRound;
shapeLayer.strokeColor = [UIColor yellowColor].CGColor;
shapeLayer.fillColor = [UIColor blueColor].CGColor;
}
return self;
}
+ (Class)layerClass {
return [CAShapeLayer class];
}
- (void) customDrawShape {
CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
[_bezierPath removeAllPoints];
[_bezierPath moveToPoint:CGPointMake(10, 10)];
[_bezierPath addQuadCurveToPoint:CGPointMake(2, 2) controlPoint:CGPointMake(50, 50)];
shapeLayer.path = _bezierPath.CGPath;
}
- (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
[super touchesBegan:touches withEvent:event];
[self customDrawShape];
}
1.Create a cocoa application (not document-based)
2.Create a new class "StretchView"(subclass NSView)
3.Open the Interface builder and drag a "Scroll view" to the main window
4.Choose the "Scroll view" and set the class "StretchView" (in class identity window)
The size of the contentview is 500*500 and the size of the strechview is also 500*500
(horizontal Scroll is enabled).
Then I start to draw some numbers(1,2,3,4......) horizontally one after the other.
When the number is out of ranger(the x pos is larger than 500) I increase the width
of the StretchView. (Everything works fine up till this point)
Then I tried to make the horizontal scroller to automatically scroll to the end so
that everytime I increase the width of the StretchView the last number coulde be
seen.
Here's the code:
//The timer is called every sec
-(void)myTimerAction:(NSTimer *) timer
{
NSLog(#"myTimerAction");
//......
int i = _myArray.count;
NSRect rect = [self frame];
int width = rect.size.width;
//The width between two number is 10
//When the x pos of current num is bigger then the scroll's width
if((i * 10) > width) {
//reset the width
width = i * 10;
[self setFrameSize:CGSizeMake(width, rect.size.height)];
//How to make it autoscroll???
//...............................
}
//......
[self setNeedsDisplay:YES];
}
Try this:
NSView *contentView = [[self enclosingScrollView] contentView];
CGFloat newXPosition = width - NSWidth([contentView bounds]);
if (newXPosition > 0.0) [self scrollPoint:NSMakePoint(newXPosition, 0.0)];
contentView is the clipping view in the enclosing scroll view. You want to scroll your current view to the x point in your view such that this x point + the clipping view width give the last clipping view width points of your view.