Banging my head on the wall with this one...
Google searches so far null...
I have a ton of over lapping circles in a mapping program...they represent radar ranges for installations such as fixed operating bases, strategic facilities, anti-aircraft assets...
Most if not all overlap one or many of their bretheren...some may stand alone...Imagine an outlying installation with limited range...
I am trying to draw the UNION of the aggregated collection of circle objects...technically ellipses bound by rectangles...
I am trying to draw the outside boundary of the air defense system...I want to eliminate all drawing of the portion of the child ellipses that fall within that outer boundry...
If an outlying station is standing alone so to speak it should be drawn as a simple circle...
Should I link a picture?
What the heck here it is...image is a bit big so I linked it
image 1024x1024
What I want to draw is union outline of the British and then of the Germans...
So far I can't figure out how to this in C# GDI...
I Do not want to fill the path using the Winding Mode Flag...I want to Draw the OUTLINE..
Any help greatly appreciated...
Oneway
Create a new image, render the circles in solid colour to that area, then overlay that image on your map at, say, 50% opacity.
Alternatively, run an edge detect on that solid-colour image to find the overall outline.
Related
I am playing around with rgl and I have created a 3D rendering of the mouse brain, in which structures can be isolated and coloured separately.
The original data is a 3D array containing evenly spaced voxels.
Every voxel is coded with a structure ID.
Every structure is rendered separately as a mesh by marching cubes, and smoothed using Laplacian smoothing as implemented by Rvcg.
Some of these structures can be quite small, and it would make sense to look at them within the context of the whole brain structure.
One of the options is to create a low-threshold mesh of the whole set of voxels, so that only the outer surface of the brain is included in the mesh.
This surface can be smoothed and represented using a low alpha in rgl::shade3d colouring faces. This however seems to be quite taxing for the viewport as it slows down rotation etc especially when alpha levels are quite low.
I was wondering if there is any way to implement some sort of cel shading in rgl, e.g. outlining in solid colours the alpha hull of the 2D projection to the viewport in real time.
In case my description was not clear, here's a photoshopped example of what I'd need.
Ideally I would not render the gray transparent shell, only the outline.
Cel shading example
Does anybody know how to do that without getting deep into OpenGL?
Rendering transparent surfaces is slow because OpenGL requires the triangles making them up to be sorted from back to front. The sort order changes as you rotate, so you'll be doing a lot of sorting.
I can't think of any fast way to render the outline you want. One thing that might work given that you are starting from evenly spaced voxels is to render the outside surface using front="points", back="points", size = 1. Doing this with the ?surface3d example gives this fake transparency:
If that's not transparent enough, you might be able to improve it by getting rid of lighting (lit = FALSE), plotting in a colour close to the background (color = "gray90"), or some other thing like that. Doing both of those gives this:
You may also be able to cull your data so the surface has fewer vertices.
What options should I use for making my graph looking like an Elipse ? I was messing with the hierarchical option under the layout module, but I've not gotten nowhere near my desired shape.
My graph is left to right, left node group connects to middle one, and middle one connects to the right one. It can be perceived as this image below.
Can someone point me in the right direction ? Thanks for your expertise
As for the elliptic shape around the nodes and edges, you can either set a background image to your graph area or create a node of large size (but this way you may have troubles with node repulsion, though). Unfortunately, there's no way to make sure that all the nodes will always be inside the ellipse (unless you access the vis' canvas and deal with it on low level or do some other hackery).
Also AFAIK it is impossible to create those wavy edges, but for those rounded ones you may want to use repulsion physics instead of barnesHut. See also physicsConfiguration example.
This seems to be a rather asked question - (hear me out first! :)
I've created a polygon with perlin noise, and it looks like this:
I need to generate a texture from this array of points. (I'm using Monogame/XNA, but I assume this question is somewhat agnostic).
Anyway, researching this problem tells me that many people use raycasting to determine how many times a line crosses over the polygon shape (If once, it's inside. twice or zero times, it's outside). This makes sense, but I wonder if there is a better way, given that I have all of the points.
Doing a small raycast for every pixel I want to fill in seems excessive - is this the only/best way?
If I have a small 500px square image I need to fill in, I'll need to do a raycast for 250,000 individual pixels, which seems like an awful lot.
If you want to do this for every pixel, you can use a sweeping line:
Start from the topmost coordinate and examine a horizontal ray from left to right. Calculate all intersections with the polygon and sort them by their x-coordinate. Then iterate all pixels on the line and remember if you are in or out. Whenever you encounter an intersection, switch to the other side. If some pixel is in, set the texture. If not, ignore it. Do this from top to bottom for every possible horizontal line.
The intersection calculation could be enhanced in several ways. E.g. by using an acceleration data structure like a grid, quadtree, etc. or by examining the intersecting or touching edges of the polygon before. Then, when you sweep the line, you will already know, which edges will cause an intersection.
I would like to draw sector of circle on map defined by point, radius, startAngle and stopAngle. I found lots of exmaples but with polygons etc whitch was too complicated for my case.
Thanks for any help!
a Circle is an object with no defined sides. Only a radius and a center point.
You are required to use a polygon to build a semi circle as it is a two sied object
There is not always an easy way out in coding, and typicaly they are the bad ways to do things (unless your talking about somthing like JQ/Bootstrap)
Here is a fairly stright forware implementation
http://googlemaps.googlermania.com/google_maps_api_v3/en/draw-semi-circle.html
This was refered in this question
Google Maps Polygon Incorrectly Rendered
they even provide a working example for you to rip apart
http://maps.forum.nu/temp/gm_bearing.html
Imagine a photo, with the face of a building marked out.
Its given that the face of the building is a rectangle, with 90 degree corners. However, because its a photo, perspective will be involved and the parallel edges of the face will converge on the horizon.
With such a rectangle, how do you calculate the angle in 2D of the vectors of the edges of a face that is at right angles to it?
In the image below, the blue is the face marked on the photo, and I'm wondering how to calculate the 2D vector of the red lines of the other face:
example http://img689.imageshack.us/img689/2060/leslievillestarbuckscor.jpg
So if you ignore the picture for a moment, and concentrate on the lines, is there enough information in one of the face outlines - the interior angles and such - to know the path of the face on the other side of the corner? What would the formula be?
We know that both are rectangles - that is that each corner is a right angle - and that they are at right angles to each other. So how do you determine the vector of the second face using only knowledge of the position of the first?
It's quite easy, you should use basic 2 point perspective rules.
First of all you need 2 vanishing points, one to the left and one to the right of your object. They'll both stay on the same horizon line.
alt text http://img62.imageshack.us/img62/9669/perspectiveh.png
After having placed the horizon (that chooses the sight heigh) and the vanishing points (the positions of the points will change field of view) you can easily calculate where your lines go (of course you need to be able to calculate the line that crosses two points: i think you can do it)
Honestly, what I'd do is a Hough Transform on the image and determine a way to identify the red lines from the image. To find the red lines, I'd find any lines in the transform that touch your blue ones. The good thing about the transform is that you get angle information for free.
Since you know that you're looking at lines, you could also do a Radon Transform and look for peaks at particular angles; it's essentially the same thing.
Matlab has some nice functionality for this kind of work.