I am working on developing a free hand drawing application for the iPad. I have just started out developing the application. I have so far succeeded in capturing the touch points. But, I am unable to render these pixels on the screen.
Are their any particular methods to perform the task? Please help!
Thank You.
Hey Amitabh,I got This while surfing,may be helpful to you. You can get the zip file of the code in the same link,they are implementing freehand tool in the application.
Thanks.
You probably want to maintain a list of points captured and render them to the UIView instance corresponding to your app's canvas. If you want a more detailed answer, we would need a more detailed question (eg, code you have so far, structure of your GUI, etc)
store the last point and use a CGContext to draw a bezier curve (CGContextAddCurveToPoint()) from the last point to the current point. You will probably need to not do this every time the touchesMoved instead make an accumulator.
static int accum = 0;
if ((accum == 0) || (accum == threshold)) {
// drawing code goes here
accum = 0;
}
accum++;
threshold should be an instance variable. You can change the threshold dynamically if you need more precision on curves.
Related
I'm on Yosemite 10.10.5 and Xcode 7, using Swift to make a game targeting iOS 8 and above.
EDIT: More details that might be useful: This is a 2D puzzle/arcade game where the player moves stones around to match them up. There is no 3D rendering at all. Drawing is already too slow and I haven't even gotten to explosions with debris yet. There is also a level fade-in, very concerning. But this is all on the simulator so far. I don't yet have an actual iPhone to test with yet and I'm betting the actual device will be at least a little faster.
I have my own Draw2D class, which is a type of UIView, set up as in this tutorial. I have a single NSTimer which initiates the following chain of calls in Draw2D:
[setNeedsDisplay]; // which calls drawRect, which is the master draw function of Draw2D
drawRect(rect: CGRect)
{
scr_step(); // the master update function, which loops thru all objects and calls their individual update functions. I put it here so that updating and drawing are always in sync
CNT = UIGraphicsGetCurrentContext(); // get the curret drawing context
switch (Realm) // based on what realm im in, call the draw function for that realm
{
case rlm.intro: scr_draw_intro();
case rlm.mm: scr_draw_mm();
case rlm.level: scr_draw_level(); // this in particular loops thru all objects and calls their individual draw functions
default: return;
}
var i = AARR.count - 1; // loop thru my own animation objects and draw them too, note it's iterating backwards because sometimes they destroy themselves
while (i >= 0)
{
let A = AARR[i];
A.scr_draw();
i -= 1;
}
}
And all the drawing works fine, but slow.
The problem is now I want to optimize drawing. I want to draw only in the dirty rectangles that need drawing, not the whole screen, which is what setNeedsDisplay is doing.
I could not find any tutorials or good example code for this. The closest I found was apple's documentation here, but it does not explain, among other things, how to get a list of all dirty rectangles so far. It does not also explicitly state if the list of dirty rectangles is automatically cleared at the end of each call to drawRect?
It also does not explain if I have to manually clip all drawing based on the rectangles. I found conflicting info about that around the web, apparently different iOS versions do it differently. In particular, if I'm gonna hafta manually clip things then I don't see the point of apple's core function in the first place. I could just maintain my own list of rectangles and manually compare each drawing destination rectangle to the dirty rectangle to see if I should draw anything. That would be a huge pain, however, because I have a background picture in each level and I would hafta draw a piece of it behind every moving object. What I'm really hoping for is the proper way to use setNeedsDisplayInRect to let the core framework do automatic clipping for everything that gets drawn on the next draw cycle, so that it automatically draws only that piece of the background plus the moving object on top.
So I tried some experiments: First in my array of stones:
func scr_draw_stone()
{
// the following 3 lines are new, I added them to try to draw in only dirty rectangles
if (xvp != xv || yvp != yv) // if the stone's coordinates have changed from its previous coordinates
{
MyD.setNeedsDisplayInRect(CGRectMake(x, y, MyD.swc, MyD.shc)); // MyD.swc is Draw2D's current square width in points, maintained to softcode things for different screen sizes.
}
MyD.img_stone?.drawInRect(CGRectMake(x, y, MyD.swc, MyD.shc)); // draw the plain stone
img?.drawInRect(CGRectMake(x, y, MyD.swc, MyD.shc)); // draw the stone's icon
}
This did not seem to change anything. Things were drawing just as slow as before. So then I put it in brackets:
[MyD.setNeedsDisplayInRect(CGRectMake(x, y, MyD.swc, MyD.shc))];
I have no idea what the brackets do, but my original setNeedsDisplay was in brackets just like they said to do in the tutorial. So I tried it in my stone object, but it had no effect either.
So what do I need to do to make setNeedsDisplayInRect work properly?
Right now, I suspect there's some conditional check I need in my master draw function, something like:
if (ListOfDirtyRectangles.count == 0)
{
[setNeedsDisplay]; // just redraw the whole view
}
else
{
[setNeedsDisplayInRect(ListOfDirtyRecangles)];
}
However I don't know the name of the built-in list of dirty rectangles. I found this saying the method name is getRectsBeingDrawn, but that is for Mac OSX. It doesn't exist in iOS.
Can anyone help me out? Am I on the right track with this? I'm still fairly new to Macs and iOS.
You should really avoid overriding drawRect if at all possible. Existing view/technologies take advantage of any hardware capabilities to make things a lot faster than manually drawing in a graphics context could, including buffering the contents of views, using the GPU, etc. This is repeated many times in the "View Programming Guide for iOS".
If you have a background and other objects on top of that, you should probably use separate views or layers for those rather than redraw them.
You may also consider technologies such as SpriteKit, SceneKit, OpenGL ES, etc.
Beyond that, I'm not quite sure I understand your question. When you call setNeedsDisplayInRect, it will add that rect to those that need to be redrawn (possibly merging with rectangles that are already in the list). drawRect: will then be called a bit later to draw those rectangles one at a time.
The whole point of the setNeedsDisplayInRect / drawRect: separation is to make sure multiple requests to redraw a given part of the view are merged together, and drawing only happens once per redraw cycle.
You should not call your scr_step method in drawRect:, as it may be called multiple times in a cycle redraw cycle. This is clearly stated in the "View Programming Guide for iOS" (emphasis mine):
The implementation of your drawRect: method should do exactly one
thing: draw your content. This method is not the place to be updating
your application’s data structures or performing any tasks not related
to drawing. It should configure the drawing environment, draw your
content, and exit as quickly as possible. And if your drawRect: method
might be called frequently, you should do everything you can to
optimize your drawing code and draw as little as possible each time
the method is called.
Regarding clipping, the documentation of drawRect states that:
You should limit any drawing to the rectangle specified in the rect
parameter. In addition, if the opaque property of your view is set to
YES, your drawRect: method must totally fill the specified rectangle
with opaque content.
Not having any idea what your view shows, what the various method you call do, what actually takes time, it's difficult to provide much more insight into what you could do. Provide more details into your actual needs, and we may be able to help.
My app already has the drawing enabled for the user on the screen. How can I define certain points in the screen and detect when the user draws through that point? Read about a few swift methods but can't quite grasp if they are applicable for what I need, also I can't find any "collision" methods.
You can use the .containspoint method. However I would recommend you to use a rectangle and not a point. It`s very difficult to draw over one certain point. So you could use CGRect for a rectangle and then again .containspoint(from the user touched point).
I have been struggling with this problem for a time and being unable to solve it led me here. I'm recently new to Actionscript (2.0). I want to do something similar to:
http://gnarshmallow.com/
Were i want something to be painted behind a moving object in real time.
I would like some advice on how to approach the problem.
You need to use line drawing to do this. You will need two points, and it will draw a line from one to the next. I recommend having it run on every movement call. Have it draw the line between the racer's location in the previous frame, and his location in the current frame. For further reference, check out this page.
http://www.actionscript.org/resources/articles/730/1/Drawing-lines-with-AS2/Page1.html
In XNA I've created a note sequence, and I'm trying to get the item to be drawn to the screen at a certain time? my check for this is a simple int that gets updated as the gametime does Convert.ToInt64(time)
is the code for that. However the only problem I got was it seemed that it kept drawing it which made the note lag? Could somebody please help?
Create a global variable that check if you draw it or not.
Once you draw it make it true.
In the update, do:
if(!variable&&time>"yourtime")
...
I am using XNA for a 2D project. I have a problem and I don't know which way to solve it. I have a texture (an image) that is drawn to the screen for example:
|+++|+++|
|---|---|
|+++|+++|
Now I want to be able to destroy part of that structure/image so that it looks like:
|+++|
|---|---|
|+++|+++|
so that collision now will work as well for the new image.
Which way would be better to solve this problem:
Swap the whole texture with another texture, that is transparent in the places where it is destroyed.
Use some trickery with spriteBatch.Draw(sourceRectangle, destinationRectangle) to get the desired rectangles drawn, and also do collision checking with this somehow.
Split the texture into 4 smaller textures each of which will be responsible for it's own drawing/collision detection.
Use some other smart-ass way I don't know about.
Any help would be appreciated. Let me know if you need more clarification/examples.
EDIT: To clarify I'll provide an example of usage for this.
Imagine a 4x4 piece of wall that when shot at, a little 1x1 part of it is destroyed.
I'll take the third option:
3 - Split the texture into 4 smaller
textures each of which will be
responsible for it's own
drawing/collision detection.
It's not hard do to. Basically it's just the same of TileSet struct. However, you'll need to change your code to fit this approach.
Read a little about Tiles on: http://www-cs-students.stanford.edu/~amitp/gameprog.html#tiles
Many sites and book said about Tiles and how to use it to build game worlds. But you can use this logic to everything which the whole is compost from little parts.
Let me quick note the other options:
1 - Swap the whole texture with
another texture, that is transparent
in the places where it is destroyed.
No.. have a different image to every different position is bad. If you need to change de texture? Will you remake every image again?
2- Use some trickery with
spriteBatch.Draw(sourceRectangle,
destinationRectangle) to get the
desired rectangles drawn, and also do
collision checking with this somehow.
Unfortunately it's don't work because spriteBatch.Draw only works with Rectangles :(
4 Use some other smart-ass way I don't
know about.
I can't imagine any magic to this. Maybe, you can use another image to make masks. But it's extremely processing-expensive.
Check out this article at Ziggyware. It is about Deformable Terrain, and might be what you are looking for. Essentially, the technique involves settings the pixels you want to hide to transparent.
Option #3 will work.
A more robust system (if you don't want to be limited to boxes) would use per-pixel collision detection. The process basically works as follows:
Calculate a bounding box (or circle) for each object
Check to see if two objects overlap
For each overlap, blit the sprites onto a hidden surface, comparing pixel values as you go. If a pixel is already set when you try to draw the pixel from the second sprite, you have a collision.
Here's a good XNA example (another Ziggyware article, actually): 2D Per Pixel Collision Detection
Some more links:
Can someone explain per-pixel collision detection
XNA 2-d per-pixel collision
I ended up choosing option 3.
Basically I have a Tile class that contains a texture and dimention. Dimention n means that there are n*n subtiles within that tile. I also have an array that keeps track of which tiles are destroyed or not. My class looks like this in pseudo code:
class Tile
texture
dimention
int [,] subtiles; //0 or 1 for each subtile
public Tile() // constructor
subtiles = new int[dimention, dimention];
intialize_subtiles_to(1);
public Draw() // this is how we know which one to draw
//iterate over subtiles
for(int i..
for(int j ...)
if(subtiles[i,j] == 1)
Vector2 draw_pos = Vector2(i*tilewidth,
j*tileheight)
spritebatch.Draw(texture, draw_pos)
In a similar fashion I have a collision method that will check for collision:
public bool collides(Rectangle rect)
//iterate over subtiles
for i...
for j..
if(subtiles[i,j]==0) continue;
subtile_rect = //figure out the rect for this subtile
if(subtile_rect.intersects(rect))
return true;
return false;
And so on. You can imagine how to "destroy" certain subtiles by setting their respective value to 0, and how to check if the whole tile is destroyed.
Granted with this technique, the subtiles will all have the same texture. So far I can't think of a simpler solution.