draw outline for some connected lines - vb.net

I have some lines that are connected at various points. I want to draw the outline of these lines and I also want to deal with the extra lines at the connection points.
I have seen two similar questions in this website: Here and here
I have handled the normal cases by offsetting the Centerlines and then changing the start and end points of the lines.
but I haven't been able to deal with special cases when the points are near each other.
Unfortunately, my reputation is low I couldn't post images to explain this better.
I'm coding in Visual Basic .net and I'm writing for Autocad, but any advice will be very useful to me.

most problem cases are solved by translation vectors intersection check
black is the original line/curve whatever ...
gray is translation vector (normal to black and size = outline distance)
blue is outline
if the translation vectors not intersect then it is most likely all OK but if they do then just do something like this:
cut off these points from outline
or create some singular point from these intersections
it is more tricky but can avoid some problem cases from bullet #1
Also sometimes help if there is bigger density of control points
Hope it helps a little...

Related

SQL Server 2012 Spatial Data Type

I am trying to draw arrows. I know how to draw lines which takes me half way there but I want the tip to have a small triangle just like an arrow. However even when I use a triangle as a point, obviously it does not always point towards the direction of the line and might sometimes produce weird looking arrows.
I would like to draw the passes a player makes on a soccer field. I do that using LINESTRING and 4 coordinates I have in a table in my database. I use the xFrom, yFrom, xTo and yTo coordinates and I manage to draw lines. However I would like to have the tip of the line to show as an arrow but I found nothing in Google or in SQL documentation.
I would like to use SSRS and not any other graphics vector program because its simpler and its incorporated easily in my overall report.
Anyone can suggest a way of turning a line into an arrow?
Thanks
Okay, first off I'd like to preface this answer with the statement that using SQL Server and Reporting Services as a graphics tool is asking for trouble. This is by far, not what it was meant for.
With that being said, I believe this would work. You will need to spend some time studying, though. When manipulating images, you have several operations that you can perform. (Like Rotating, skewing, resizing, etc.) The mathematics behind these operations can be performed using matrix algebra. What you will need to do is look at the line you have created. It has a slope. If you picture that line superimposed upon X and Y axes, you can see that there is an angle between the line and the Y axis. (Assumes that the triagle's base rests upon the X axis.) That angle is the angle that you will want to rotate your triangle that you're using as the tip of the arrow. That should fix your problem. You could create a formula to do the calculations. (If the formula engine is robust enough to handle matrix algebra.)
Here are a couple of pages that give you the basics of how to rotate an image.
http://datagenetics.com/blog/august32013/index.html
http://www.fastgraph.com/makegames/3drotation/
Good luck!

Check if circles completely cover an area

Starting with an arbitrary rectangle, a user can place any number of circles within.
The circles are allowed to overlap each other without restrictions.
The circles can be of different sizes.
What would be the best way to test if the rectangle is completely covered by the circles?
It seems a very tricky algorithm, but fortunately dsomebody thought about it before :)
Check this question:
https://cs.stackexchange.com/questions/11163/circles-covering-a-rectangular-how-to-verify-it
Seems to have the same problem as you.
I eventually found that the simplest solution (for me anyway) in both JS and Objective-C was to simply iterate of over each pixel and check for the colour (assuming circles are coloured) and check if it was the colour of a circle (or it's border). As soon as a colour from a circle was found then iteration stops as the area is obviously not fully covered by the shapes.
The advantage to this solution is that the actual shape doesn't matter (we ended up adding other shapes also).

Detect multiple bodies in Kinect?

I am working with kinect in openframework using the ofxKinect addon, which is great and plenty fun!
Anyway I am looking for some pointers or a direction when dealing with multiple bodies on the screen. I was thinking of making a rect around each detected body and when the rects intersect something could happen, an effect or anything.
So what I am looking for are ideas or something that could point me to the right direction of detecting multiple bodies when using a kinect.
Right now based on the depth image I get from the kinect I go through each pixel and create a bunch of smaller rectangles with a padding and group them in a larger rectangle bound if they are separate from another rectangle group. This is not ideal as it only deals with the pixel values and is not really seperating bodies from eachother and is not giving me the results I am looking for.
So any ideas would be greatly appreciated!
If you want to use ofxKinect a quick solution would be to threshold on depth and assume bodies and no other objects will be within a depth range. This should make it easy to use the OpenCV's contour finder to isolate the outlines of the bodies and get the bounding rectangles. If the rectangles intersect(and ofRectangle already does the math you), trigger the reaction you need. Also don't forget to do that once if the effect isn't showing already, otherwise you will trigger the effect multiple times per second while the two bodies' bounding rectangles intersect.
You could try something a bit more hardcore and using ofxCv(not just ofxOpenCV) to tap into the HoG functionality. This is slow in itself and not ideal with the depth map, but hopefully you can run in every few seconds just to detect a person and the depth, then keep tracking that movement.
Personally, if you want to track people with the Kinect I recommend using ofxOpenNI as if already provides the scene segmentation feature and even if you don't track the skeletons you can still get useful information like the pixels pertaining to each body and they're centre of mass. I'm guessing Microsoft KinectSDK has a similar feature and there should be an oF addon, but it's windows only.
ofxKinect/libfreenect does not offer any people detection features, so you will need to roll your own.

top down game - checking, drawing enemy's line of sight area with obstacles

Examples of what i'm going to need:
I'm using cocos2d to draw a CCTMXTiledMap, on those tiles i'll have to draw the LOS triangle.
How would i test if the player is within that triangle, taking obstacles into account?
How would i draw the line of sight area like in the examples above?
BTW, i wasn't sure if this should have been posted here or on gamedev, don't be mad.
You may wish to look at point-in-polygon algorithms such as the ray casting algorithm described here.
You can break up the triangle to account for obstacles, or just make a more complex polygon. You should be able to find an implementation to suit your needs online.
You may also want to take a look at this article for some inspiration. You can maintain a tree like structure, a root triangle (or fulcrum) that can be used to determine whether a point is in general line of sight, with the children (triangles) taking obstacles into account. That way you can quickly eliminate more complex checks.
In the image below the dark blue dots are quickly eliminated from further checking as they do not fall within the root viewing triangle.

Straight Line Equation between two points

I need to paint the line which links two points.
I am doing it, in Java. I receive two points as parameters and I have to calculate if the straight line between them, is inside the black figure.
I developed my own solution using the straight line equation, but my results are different than using the "professional" programs (such as GIMP or even MS Paint).
Here is a example of what I want:
alt text http://img411.imageshack.us/img411/788/img1q.png
But my algorithm does this:
alt text http://img267.imageshack.us/img267/1908/img2d.png
*The green point is out of the figure and this is not possible.
Any ideas? Anyone know which code is been using for this, in "professional" apps?
Thanks!
Daniel.
EDIT: Images
It looks like you are truncating instead of rounding to the nearest pixel. Difficult to see on those small black ink splotches. Could you post the code?
"Professional" programs most likely use Bresenham's line algorithm.
Look at Bresenham's line drawing algorithm
Straignt lines are drawn using Bresenham's algorithm usually. I didn't get your point about green point being out of the figure - there's clipping to not waste time drawing outside the visible area.