in my previous code, I changed the coordinate system in my view's drawRect, so that the rectangle had 0,0 in the centre, 0,1 at the top centre and 1,0 in the centre of the right edge. I.e. a normalised Cartesian system.
{
// SCALE so that we range from TL(0, 0) - BR(2, -2)
CGContextScaleCTM (X, 0.5 * bitmapSize.width, -0.5 * bitmapSize.height);
// TRANSLATE so that we range from TL(-1, 1) - BR(1, -1)
// ie: a cartesian coordinate system, centred on (0, 0) with:
// x increasing to the right
// y increasing upwards
// x&y each ranging from -1 to 1
CGContextTranslateCTM(X, 1, -1);
T = CGContextGetCTM (X);
}
in this box I create a wheel with 12 custom drawn buttons arranged around it. The buttons glow before gradually fading when pressed.
now I am redesigning the code, as the animation was rendering far too slowly
in my view's Load event I create a wheel object, which draws the wheel onto its own CALayer. this is then added as a sublayer to the view's Layer.
( the wheel object will in turn create the buttons which will each draw onto their own CALayer, and these layers will be added as sub layers to the wheels layer )
anyway, I would very much like to perform the drawing of the wheel and the buttons using my normalised Cartesian system. But I can't quite see how to implement it.
I could change the views transform. But this changes the boundary rectangle of the view. One solution would be to have a view within a view, but I discovered by chance testing that clipping to a circular path and drawing within that path will substantially slower than drawing without the clip. So I am hesitant to do this. I am looking for optimal efficiency (without going to GL, just yet -- I'm not ready for that -- I need to understand this stuff first, I think)
alternatively I could change the transform of the layer. but this is a 3D transform! I am having a lot of trouble getting my head around the logic of this. IPhone is a 2D screen. On it is represented a 2D interface. views and layers I conceptualise as flat rectangles sitting on top of one another. Is this wrong? Is this 3-D business just to do funky flip effects?
what if the layer has been set to rasterize, and it has a weird transform? How can it rasterize if it doesn't know what pixel resolution it is running? what if we have 10 nested layers each with a funky transform? And the innermost one needs to be rasterised? Does it somehow go all the way down the chain and figure out what pixels it is to overlay? What if the base layer is within a view within a view within a view and these views have 2D transforms on them? Does it really go all the way until it gets to pixel?
I want to rasterize my buttons -- that's why I'm asking. They are very complex drawing objects. It would save a lot of CPU GPU if they were prerendered dead and alive, and the fading would simply consist of compositing x*dead plus (1-x)*alive. so really I want bitmaps for both.
could someone slay my confusion?
many thanks,
Ohmu
Related
I am currently trying to map textures using image labels onto 2 different triangles (because im using right angle wedges so i need 2 to make scalene triangles), but here is the problem, I can only set positional, size, and rotational data so I need to figure out how I can use this information to correctly map the texture onto the triangle
the position is based on the topleft corner and size of triangle (<1,1> corner is at the bottom right and <0,0> corner is at top left) and the size is based on triangle size also (<1,1> is same size as triangle and <0,0> is infinitely tiny) and rotation is central based.
I have the UV coordinates (given 0-1) and face vertices, all from an obj file. The triangles in 3D are made up of 2 wedges which are split at a right angle from the longest surface and from the opposite angle.
I don't quite understand this however it may be help to change the canvas properties on the Surface GUI
I have successfully implemented shadow maps in my engine but the problem is the shadow map doesn't cover the whole scene. If I make the shadowmap large shadow quality will drop. So I'm trying make my shadows move with camera. I can do this if I can calculate the 8 world space positions of camera frustum vertices.
So how can I calculate world space positions of camera frustum vertices ? I'm working with Directx if it changes the way how it's calculated.
Thanks.
The frustum (near plane, far plane, fov) is in view space so multiplying it with an inverse view matrix will move it into world space. If you use DirectXMath (which I recommend) you can utilize the bounding frustum object. An example code might look something like this:
DirectX::BoundingFrustum frustum;
DirectX::BoundingFrustum::CreateFromMatrix(frustum, camera.getProjectionMatrix());
DirectX::XMMATRIX inverseViewMatrix = DirectX::XMMatrixInverse(nullptr, camera.getViewMatrix());
frustum.Transform(frustum, inverseViewMatrix);
BoundingFrustum docs: https://msdn.microsoft.com/en-us/library/windows/desktop/microsoft.directx_sdk.directxmath.boundingfrustum(v=vs.85).aspx
If your frustum is big and you have to view a large area (e.g. outdoor scene) then even a large moving shadow map might not be enough (or it takes a huge amount of memory). One technique to solve this is called cascaded shadow maps (CSM). In CSM more precise shadow maps are rendered close to the camera and less precise shadows are rendered in the distance where the low quality is not visible anyway. Here is a CSM tutorial in case you are interested: https://msdn.microsoft.com/en-us/library/windows/desktop/ee416307(v=vs.85).aspx
I want to draw a line with dynamic width as shown in attached picture. What should be the best approach for this. ?
Updated:
My task is to draw line on finger move. And the line width is changes as speed of swipe is change. both (Line width and finger swipe speed) are directly proportional .
As the image you posted doesn't has any consistent height-width proportion to calculate and change, i doubt this cannot be achieved.
In other solution you can draw a line of fixed pixel say 2 pixel and based on drawn length inflate the width if line till center and then again start deflate from center point to end point.
You need to see the difference between x coordinates otherwise if a sine wave is drawn with high nodes the line width will overlap each other.
Edited : This link might be of your interest then.You can modify it according to your need, its in cocos2d.
There is no direct support for variable thickness curves in iOS (or Mac OS for that matter.) The cocos2d project looks like a good approach.
There is also no support for soft-edged curves who's edges are feathered to transparent. I've thought about implementing a similar approach to the one outlined in the Cocos link using OpenGL. This would be a good application for a vertex shader, since it would take advantage of the parallel vertex processing and vector math available in shaders.
Take a look at this article Smooth Freehand Drawing. It might be helpfull.
You can manipulate with control points of
[path addCurveToPoint:pts[3] controlPoint1:pts[1] controlPoint2:pts[2]];
and fill the area between two bezierPaths. I am not sure if it will work, but you can try if you dont find anything else.
How to draw a circle overlapping another circle in the moved phase of touch event,such that no gap is left out between the circles.The circles must be tightly packed to one another,so that even when user moves his hand on the screen faster or lightly,no gap must be present between the circles.
Just two circles? Or many circles? If just two, then detecting if they overlap is simply verifying that their centers are not closer than the sum of their radii. For example, if Circle1's raduis is 10 pixels, and Circle2's radius is 25 pixels, then they overlap if the center of Circle1 is less than 35 pixels from the center of Circle2.
So if you do your calculations in the "moved" phase and find that they're too close, you have to adjust the position of one of them. How you go about that will depend on the specifics of your application. You could:
Keep the y coordinate of the moving circle the same, and calculate the necessary x coordinate to maintain the required distance.
Same as above but swap x and y.
As above, but move the "unmoving" circle away from the "moving" circle.
Some other calculation that makes sense for your application.
NOTE: You should accept some of the answers you've been given.
I have a texture with 250px width and 2000px height. 250x250 part of it drawn on screen according to various conditions (some kind of sprite sheet, yes). All I want is to draw it within a fixed destination rectangle with some rotation. Is it possible?
Yes. Here's how to effectively rotate your destination rectangle:
Take a look at the overloads for SpriteBatch.Draw.
Notice that none of the overloads that take a Rectangle as a destination take a rotation parameter. It's because such a thing does not make much sense. It's ambiguous as to how you want the destination rotated.
But you can achieve the same effect as setting a destination rectangle by careful use of the position and scale parameters. Combine these with the origin (centroid of scaling and rotation, specified in pixels in relation to your sourceRectangle) and rotation parameters to achieve the effect you want.
(If, on the other hand, you want to "fit" to a rectangle - effectively scaling after rotating - you would have to also use the transformMatrix parameter to Begin.)
Now - your question isn't quite clear on this point: But if the effect you are after is more like rotating your source rectangle, this is not something you can achieve with plain ol' SpriteBatch.
The quick-and-dirty way to achieve this is to set a viewport that acts as your destination rectangle. Then draw your rotated sprite within it. Note that SpriteBatch's coordinate system is based on the viewport, not the screen.
The "nicer" (but much harder to implement) way to do it would be to not use SpriteBatch at all, but implement your own sprite drawing that will allow you to rotate the texture coordinates.