I would like draw a curved line and attach an object to it. Is it possible to create fraction (from 0.0 to 1.0) which makes move my object on the path? When fraction is 0 then object is on the beginning, when 0.5 is on half way and finally when is on 1.0 it is at the end. Of course i want a curved path, not a straight line :) Is it possible to do in PaintCode?
If you need it only as a progress bar, it is possible in PaintCode. The trick is to use dashed stroke with very large Gap and then just change the Dash.
Then just attach a Variable and you are done.
Edit: Regarding the discussion under the original post, this solution uses points as the unit, so it will be distributed equally along the curve, no matter how curved the bezier is.
Based on the fact that you're going to walk along the curve using linear distance, a thing Bezier curves are terrible for, you need to build the linear mapping yourself. That's fairly simple though:
When you draw the curve, also build a look-up table that samples the curve once, at say 100 points (t=0, t=0.01, t=0.02, etc). In pseudocode:
lut = [];
lut[0] = 0;
tlen = curve.length();
for(v=0; v<=100; v++) {
t = v/100;
clen = curve.split(0,t).length();
percent = 100*clen/tlen;
lut[percent] = t;
}
This may leave gaps in your LUT - you can either fix those as a secondary step, or just leave them in and do a binary scan on your array to find the nearest "does have a value" percentage.
Then, when you need to show your progress as some percentage value, you just look up the corresponding t value: say you need to show 83%, you look up lut[83] and draw your object at the value that gives you.
Related
I experienced that for some NSBezierPaths SCNShape seems to be unable to draw a shape.
The path is created only using line(to:).
//...set up scene...
//Create path (working)
let path = NSBezierPath()
path.move(to: CGPoint.zero)
path.line(to: NSMakePoint(0.000000, 0.000000))
path.line(to: NSMakePoint(0.011681, 0.029526))
// more points ...
path.close()
// Make a 3D shape (not working)
let shape = SCNShape(path: path, extrusionDepth: 10)
shape.firstMaterial?.diffuse.contents = NSColor.green
let node = SCNNode(geometry: shape)
root.addChildNode(node)
For verifying that the general process of creating a SCNShape is correct, I also drew a blue shape that only differs by having different points. The blue shape gets drawn, the green shape doesn't.
You can find a playground containing the full example here. In the example you should be able to see a green and a blue shape in assistant editor. But only the blue shape gets drawn.
Do you have any idea why the green shape is not shown?
The short story: your path has way more points than it needs to, leading you to unexpected, hard to find geometric problems.
Note this bit in the documentation:
The result of extruding a self-intersecting path is undefined.
As it turns out, somewhere in the first 8 or so points, your "curve" makes enough of a turn the wrong way that the line closing the path (between the first point in the path 0,0, and the last point 32.366829, 29.713470) intersects the rest of the path. Here's an attempt at making it visible by excluding all but the first few points and the last point from a playground render (see that tiny little zigzag in the bottom left corner):
And at least on some SceneKit versions/renderers, when it tries to make a mesh out of a self-intersecting path it just gives up and makes nothing.
However, you really don't need that many points to make your path look good. Here it is if you use 1x, 1/5x, and 1/10x as many points:
If you exclude enough points overall, and/or skip the few at the beginning that make your curve zag where it should zig, SceneKit renders the shape just fine:
Some tips from diagnosing the problem:
When working with lots of coordinate data like this, I like to use ExpressibleByArrayLiteral so I can easily build an array of lots of points/vectors/etc:
extension CGPoint: ExpressibleByArrayLiteral {
public init(arrayLiteral elements: CGFloat...) {
precondition(elements.count == 2)
self.init(x: elements.first!, y: elements.last!)
}
}
var points: [CGPoint] = [
[0.000000, 0.000000],
[0.011681, 0.029526],
// ...
]
That gets me an array (and a lot less typing out things like NSPointMake over and over), so I can slice and dice the data to figure out what's wrong with it. (For example, one of my early theories was that there might be something about negative coordinates, so I did some map and min() to find the most-negative X and Y values, then some more map to make an array where all points are offset by a constant amount.)
Now, to make paths using arrays of points, I make an extension on NSBezierPath:
extension NSBezierPath {
convenience init(linesBetween points: [CGPoint], stride: Int = 1) {
precondition(points.count > 1)
self.init()
move(to: points.first! )
for i in Swift.stride(from: 1, to: points.count, by: stride) {
line(to: points[i])
}
}
}
With this, I can easily create paths from not just entire arrays of points, but also...
paths that skip parts of the original array (with the stride parameter)
let path5 = NSBezierPath(linesBetween: points, stride: 5)
let path10 = NSBezierPath(linesBetween: points, stride: 10)
(This is handy for generating playground previews a bit more quickly, too.)
paths that use some chunk or slice of the original array
let zigzag = NSBezierPath(linesBetween: Array(points.prefix(to:10)) + [points.last!])
let lopOffBothEnds = NSBezierPath(linesBetween: Array(points[1 ..< points.count < 1]))
Or both... the winning entry (in the screenshot above) is:
let path = NSBezierPath(linesBetween: Array(points.suffix(from: 10)), stride: 5)
You can get a (marginally) better render out of having more points in your path, but an even better way to do it would be to make a path out of curves instead of lines. For extra credit, try extending the NSBezierPath(linesBetween:) initializer above to add curves by keeping every nth point as part of the path while using a couple of the intermediary points as control handles. (It's no general purpose auto trace algorithm, but might be good enough for cases like this.)
In no way does this compare to Rikster's answer, but there is another way to prevent this kind of problem. It's a commercial way, and there's probably freeware apps that do similar, but this is one I'm used to using, that does this quite well.
What is 'this' that I'm talking about?
The conversion of drawings to code, by an app called PaintCode. This will allow you to see your paths and be sure they have none of the conflicts that Rickster pointed out are your issue.
Check it out here: https://www.paintcodeapp.com/
Other options are listed in answers here: How to import/parse SVG into UIBezierpaths, NSBezierpaths, CGPaths?
I have some experience with Metal and quite a bit with Unity and am familiar with setting up meshes, buffers, and the backing data for drawing; but not so much the math/shader side. What I'm struggling with is how to get an endless scrolling world. So if I pan far to the right side I can see the left side and keep going.
The application of this would be a seamless terrain that a player could scroll in any direction forever and have it just wrap.
I don't want to duplicate everything on draw and offset it, that seems horrendously inefficient. I am hoping for a way to either use some magic matrix math or some sort of shader to get things wrapping/drawing where they should when panning the map. I've searched all over for some sort of guide or explanation of how to get this working but haven't come up with anything.
I know a lot of old (dos) games did this somehow, is it still possible? Is there a reason why it seems the industry has migrated away from this type of scrolling (bounding to edges vs wrapping)?
I have created a simple example demonstrating what you're looking for (I think).
The basic idea of it is that you draw the map in a repeating grid, using the drawPrimitives(type:vertexStart:vertexCount:instanceCount:) method on MTLRenderCommandEncoder. As the instance count you want to pass in the number of identical maps you want to draw, extending it as far as needed to not see where it ends. In my example I used a simple 5x5 grid.
To not have the user see the edge of the map, we're gonna calculate their position modulo 1 (or whatever size your map is):
func didDrag(dx: CGFloat, dy: CGFloat) {
// Move user position on drag, adding 1 to not get below 0
x += Float(dx) * draggingSpeed + 1
z += Float(dy) * draggingSpeed + 1
x.formTruncatingRemainder(dividingBy: 1)
z.formTruncatingRemainder(dividingBy: 1)
}
This is how it looks:
Just a follow up on what I have actually implemented. First I essentially have an array of x,y points with altitude, terrain type and all that jazz. Using some simple % and additions/subtractions it is trivial to get the nodes around a point to generate triangles
On a draw I calculate the first showing point and the last showing point and calculate the groups of triangles shown between those points. The first/last point take into account wrapping, it is then pretty trivial to have an endless wrapping world. For each group a translation offset is passed via a uniform matrix for that group which will position that section where it should belong.
I set it via renderEncoder.setVertexBytes(&uniform, length:..., offset:...)
I am currently working on an algorithm to detect the playing area of a pool table. For this purpose, I captured an image, transformed it to grayscale, and used a Sobel operator on it. Now I want to detect the playing area as a box with 4 corners located in the 4 corners of the table.
Detecting the edges of the table is quite straightforward, however, it turns out that detecting the 4 corners is not so easy, as there are pockets in the pool table. Now I just want to fit a line to each of the side edges, and from those lines, I can compute the intersects, which are the corners for my table.
I am stuck here, because I could not yet come up with a good solution to find these lines in my image. I can see it very easily when I used the Sobel operator. But what would be a good way of detecting it and computing the position of the corners?
EDIT: I added some sample Images
Basic Image:
Grayscale Image
Sobel Filter (horizontal only)
For a general solution, there will be many sources of noise: problems with cloth around the rails, wood texture (or no texture) on the rails, varying lighting, shadows, stains on the cloth, chalk on the rails, and so on.
When color and lighting aren't dependable, and when you want to find the edges of geometric objects, then it's best to think in terms of edge pixels rather than gray/color pixels.
A while back I was thinking of making a phone-based app to save ball positions for later review, including online, so I've though a bit about this problem. Although I can provide some guidance for your current question, it occurs to me you'll run into new problems each step of the way, so I'll try to provide a more complete answer.
Convert the image to grayscale. If we can't get an algorithm to work in grayscale, we'll inevitably run into problems with color. (See below)
[TBD] Do some preprocessing to reduce noise.
Find edge points using Sobel or (if you must) Canny.
Run Hough lines detection, but with a few caveats and parameterizations as described below.
Find the lines described a keystone-shaped quadrilateral. (This will likely be the inner quadrilateral of two: one inside the rail on the bed, and the other slightly larger quadrilateral at the cloth/wood rail edge at top.)
(Optional) Use the side pockets to help determine the orientation of the quadrilateral.
Use an affine transform to map the perspective-distorted table bed to a rectangle of [thankfully] known relative dimensions. We know the bed sizes in advance, so you can remap the distorted rectangle to a proper rectangle. (We'll ignore some optical effects for now.)
Remap the color image to the perspective-corrected rectangle. You'll probably need to tweak the positions of some balls.
General notes:
Filtering by color in the general sense can be difficult. It's tempting to think of the cloth as being simply green, blue, or red (or some other color), but when you look at the actual RGB values and try to separate colors you'll begin to appreciate what a nightmare working in color can be.
Optical distortion might throw off some edges.
The far short rail may be difficult to detect, BUT you do this: find the inside lines for the two long rails, then search vertically between the two rails for the first strong horizontal-ish edge at the far side of the image. That'll be the far short rail.
Although you probably want to use your phone camera for convenience, using a Kinect camera or similar (preferably smaller) device would make the problem easier. Not only would you have both color data and 3D data, but you would eliminate some problems with lighting since the depth data wouldn't depend on visible lighting.
For your app, consider limiting the search region for rail edges to a perspective-distorted rectangle. The user might be able to adjust the search region. This could greatly simplify the processing, and could help you work around problems if the table isn't lit well (as can be the case).
If color segmentation (as suggested by #Dima) works, get the outline of the blob using contour following. Then simplify the outline to a quadrilateral (or a polygon of few sides) by the Douglas-Peucker algorithm. You should find the four table edges this way.
For more accuracy, you can refine the edge location by local search of transitions across it and perform line fitting. Then intersect the lines to get the corners.
The following answer assumes you have already found the positions of the lines in the image. This however can be done "easily" by directly looking at the pixels and seeing if they are in a "line". Usually it is easier to detect this if the image has been deskewed first as well, i.e. Rotated so the rectangle (pool table) is more like this: [] than like /=/. Then it is just a case of scanning the pixels and if there are ones of similar colour alongside it assuming a line is between them.
The code works by looping over the lines found in the image. Whenever the end points of each line falls within a tolerance on within the x and y coordinates it is marked as a corner. Once the corners are found I take the average value between them to find where the corner lies. For example:
A horizontal line ending at 10, 10 and a vertical line starting at 12, 12 will be found to be a corner if there is a tolerance of 2 or more. The corner found will be at: 11, 11
NOTE: This is just to find Top Left corners but can easily be adapted to find all of them. The reason it has been done like this is because in the application where I use it, it is faster to sort each array first into an order where relevant values will be found first, see: Why is processing a sorted array faster than an unsorted array?.
Also note that my code finds the first corner for each line which might not be applicable for you, this is mainly for performance reasons. However the code can easily be adapted to find all the corners with all the lines then either select the "more likely" corner or average through them all.
Also note my answer is written in C#.
private IEnumerable<Point> FindTopLeftCorners(IEnumerable<Line> horizontalLines, IEnumerable<Line> verticalLines)
{
List<Point> TopLeftCorners = new List<Point>();
Line[] laHorizontalLines = horizontalLines.OrderBy(l => l.StartPoint.X).ThenBy(l => l.StartPoint.Y).ToArray();
Line[] laVerticalLines = verticalLines.OrderBy(l => l.StartPoint.X).ThenBy(l => l.StartPoint.Y).ToArray();
foreach (Line verticalLine in laVerticalLines)
{
foreach (Line horizontalLine in laHorizontalLines)
{
if (verticalLine.StartPoint.X <= (horizontalLine.StartPoint.X + _nCornerTolerance) && verticalLine.StartPoint.X >= (horizontalLine.StartPoint.X - _nCornerTolerance))
{
if (horizontalLine.StartPoint.Y <= (verticalLine.StartPoint.Y + _nCornerTolerance) && horizontalLine.StartPoint.Y >= (verticalLine.StartPoint.Y - _nCornerTolerance))
{
int nX = (verticalLine.StartPoint.X + horizontalLine.StartPoint.X) / 2;
int nY = (verticalLine.StartPoint.Y + horizontalLine.StartPoint.Y) / 2;
TopLeftCorners.Add(new Point(nX, nY));
break;
}
}
}
}
return TopLeftCorners;
}
Where Line is the following class:
public class Line
{
public Point StartPoint { get; private set; }
public Point EndPoint { get; private set; }
public Line(Point startPoint, Point endPoint)
{
this.StartPoint = startPoint;
this.EndPoint = endPoint;
}
}
And _nCornerTolerance is an int of a configurable amount.
A playing area of a pool table typically has a distinctive color, like green or blue. I would try a color-based segmentation approach first. The Color Thresholder app in MATLAB gives you an easy way to try different color spaces and thresholds.
I've ran in to an issue concerning generating floating point coordinates from an image.
The original problem is as follows:
the input image is handwritten text. From this I want to generate a set of points (just x,y coordinates) that make up the individual characters.
At first I used findContours in order to generate the points. Since this finds the edges of the characters it first needs to be ran through a thinning algorithm, since I'm not interested in the shape of the characters, only the lines or as in this case, points.
Input:
thinning:
So, I run my input through the thinning algorithm and all is fine, output looks good. Running findContours on this however does not work out so good, it skips a lot of stuff and I end up with something unusable.
The second idea was to generate bounding boxes (with findContours), use these bounding boxes to grab the characters from the thinning process and grab all none-white pixel indices as "points" and offset them by the bounding box position. This generates even worse output, and seems like a bad method.
Horrible code for this:
Mat temp = new Mat(edges, bb);
byte roi_buff[] = new byte[(int) (temp.total() * temp.channels())];
temp.get(0, 0, roi_buff);
int COLS = temp.cols();
List<Point> preArrayList = new ArrayList<Point>();
for(int i = 0; i < roi_buff.length; i++)
{
if(roi_buff[i] != 0)
{
Point tempP = bb.tl();
tempP.x += i%COLS;
tempP.y += i/COLS;
preArrayList.add(tempP);
}
}
Is there any alternatives or am I overlooking something?
UPDATE:
I overlooked the fact that I need the points (pixels) to be ordered. In the method above I simply do scanline approach to grabbing all the pixels. If you look at the 'o' for example, it would grab first the point on the left hand side, then the one on the right hand side. I would need them to be ordered by their neighbouring pixels since I want to draw paths with the points later on (outside of opencv).
Is this possible?
You should look into implementing your own connected components labelling. The concept is very simple: you scan the first line and assign unique labels to each horizontally connected strip of pixels. You basically check for every pixel if it is connected to its left neighbour and assign it either that neighbour's label or a new label. In the second row you do the same, but you also check against the pixels above it. Sometimes you need a label merge: two strips that were not connected in the previous row are joined in the current row. The way to deal with this is either to keep a list of label equivalences or use pointers to labels (so you can easily do a complete label change for an object).
This is basically what findContours does, but if you implement it yourself you have the freedom to go for 8-connectedness and even bridge a single-pixel or two-pixel gap. That way you get "almost-connected components labelling". It looks like you need this for the "w" in your example picture.
Once you have the image labelled this way, you can push all the pixels of a single label to a vector, and order them something like this. Find the top left pixel, push it to a new vector and erase it from the original vector. Now find the pixel in the original vector closest to it, push it to the new vector and erase from the original. Continue until all pixels have been transferred.
It will not be very fast this way, but it should be a start.
How to make a 2d world with fixed size, which would repeat itself when reached any side of the map?
When you reach a side of a map you see the opposite side of the map which merged togeather with this one. The idea is that if you didn't have a minimap you would not even notice the transition of map repeating itself.
I have a few ideas how to make it:
1) Keeping total of 3x3 world like these all the time which are exactly the same and updated the same way, just the players exists in only one of them.
2) Another way would be to seperate the map into smaller peaces and add them to required place when asked.
Either way it can be complicated to complete it. I remember that more thatn 10 years ago i played some game like that with soldiers following each other in a repeating wold shooting other AI soldiers.
Mostly waned to hear your thoughts about the idea and how it could be achieved. I'm coding in XNA(C#).
Another alternative is to generate noise using libnoise libraries. The beauty of this is that you can generate noise over a theoretical infinite amount of space.
Take a look at the following:
http://libnoise.sourceforge.net/tutorials/tutorial3.html#tile
There is also an XNA port of the above at: http://bigblackblock.com/tools/libnoisexna
If you end up using the XNA port, you can do something like this:
Perlin perlin = new Perlin();
perlin.Frequency = 0.5f; //height
perlin.Lacunarity = 2f; //frequency increase between octaves
perlin.OctaveCount = 5; //Number of passes
perlin.Persistence = 0.45f; //
perlin.Quality = QualityMode.High;
perlin.Seed = 8;
//Create our 2d map
Noise2D _map = new Noise2D(CHUNKSIZE_WIDTH, CHUNKSIZE_HEIGHT, perlin);
//Get a section
_map.GeneratePlanar(left, right, top, down);
GeneratePlanar is the function to call to get the sections in each direction that will connect seamlessly with the rest of your world.
If the game is tile based I think what you should do is:
Keep only one array for the game area.
Determine the visible area using modulo arithmetics over the size of the game area mod w and h where these are the width and height of the table.
E.g. if the table is 80x100 (0,0) top left coordinates with a width of 80 and height of 100 and the rect of the viewport is at (70,90) with a width of 40 and height of 20 you index with [70-79][0-29] for the x coordinate and [90-99][0-9] for the y. This can be achieved by calculating the index with the following formula:
idx = (n+i)%80 (or%100) where n is the top coordinate(x or y) for the rect and i is in the range for the width/height of the viewport.
This assumes that one step of movement moves the camera with non fractional coordinates.
So this is your second alternative in a little bit more detailed way. If you only want to repeat the terrain, you should separate the contents of the tile. In this case the contents will most likely be generated on the fly since you don't store them.
Hope this helped.