I need to know how to determine fast if line intersects simple polygon.
It should work in O(log n) time, where n is number of polygon's vertexes.
I searched in google, but I didn't find anything useful, maybe I'm blind. ;)
Edit: I'm using C++ but I think language isn't a problem, and it isn't homework, just doing some algorithms training. Geometry is sick. ;)
Oh. I forgot it's only in 2d.
Thanks for future and actual help.
I've found a paper who solves this problem really fast:
"Fast MinimumStorage RayTriangle Intersection"
http://www.cs.virginia.edu/~gfx/Courses/2003/ImageSynthesis/papers/Acceleration/Fast%20MinimumStorage%20RayTriangle%20Intersection.pdf
EDIT: It even contains code :)
Related
I did and exam a while ago and one of the questions asked to find a formula for an "equilateral ellipse". In my mind an equilateral ellipse should be a circle, but it seems I am wrong.
I searched online for the term, but didn't find anything useful. Does anyone know what it is, can find a formula and give me some references?
Thanks,
Douglas.
I believe an "equilateral ellipse" is a circle, as you suspected.
Or at least that is old terminology:
Coleman, Percy. Co-ordinate geometry: An elementary course. Clarendon Press, 1914.
I am applying A* (and IDA*) search with manhattan heuristic for finding solution to 15-puzzle problem.
Using the fact that i dont want an optimal solution for the problem how can i can speed up the search as the current routine is too slow.
Well, it's not exactly a solution, but it might help. Once I've been working for a HOG game with that same puzzle as a minigame and it turned much easier to generate a problem, than find a solution.
What I mean is, we can turn a solved puzzle into unsolved by randomly moving "window" according to rules. And logging each field position for future use. Then we let user play a bit and if she gives up, we can solve a puzzle for her easily by finding the common position in user and our log. We just play back via user log to the common position and back from it to the solved position via ours log.
Of course, this is a hack and not a real solution, but it works fine in gamedev. And not only for this particular game. Most repositioning puzzles can be "solved" this way.
I'm raytracing and would like to speed it up via some acceleration structure (kd-tree, BVH, whatever). I don't want to code it up myself. What I've tried so far:
Yanking the kd-tree out of pbrt. There are so many intra-dependencies that I couldn't succeed at this without pulling all of pbrt into my code.
CGAL's AABB tree. Frustratingly, this seems to return only the point of intersection. Without knowing which triangle the point came from, I can't efficiently interpolate color over the triangle. I'd love to just extend the notion of "Point" with color, but this doesn't seem possible without writing a lot of template code from scratch.
Writing my own. Okay so I wrote my own grid acceleration class, and it works, but it's nasty and inefficient.
So, if anyone can suggest a simple library that I can use for this purpose I'd really appreciate it! All I need is given a triangle soup and ray, find the closest intersection and return the index of that triangle.
Jaco Bikker wrote this series of tutorials: http://www.devmaster.net/articles/raytracing_series/part7.php
They're very helpful and he includes code at the end for a ray tracer using a kd-tree.
You might be able to use that.
The G3D engine has a ray tracing implementation. Not sure how efficient it is though. It shouldn't bee too much trouble to use the Tree implementation without the rest of the library.
I am working on nesting of sheet metal parts and am implementing Minkowski Sums to find No Fit Polygons for nesting. The problem is I can give only convex sets as input to the code which calculates Minkowski sums for me. Hence I need to break a concave polygon, with holes into Convex sets. I am open to triangulation also, but I am looking for a working code on VC++ (6.0). I am slightly running short on time as my whole code is ready and just waiting for input in the form of convex sets.
I would really appreciate if somebody with prior experience can help me in this. I have gone through other posts but did not find anything matching to this. I am a student of mechanical engineering and really dun have much idea about computer languages. All I can handle is compiling a code on VC++ and incorporate it with my existing code.
If you have access to OpenGL, you can take advantage of GLU's tessellation. You don't have to actually use OpenGL to use the tessellator, but I leave that as an exercise to the reader.
Now that Wolfram Alpha is released, I am interested in finding out if it can be used as a time-saver in daily programming.
What would you use Wolfram Alpha to do, that earlier took you more time to do manually?
I guess the "Web and Computer systems"-examples is a good start, but there must be more hidden gems that will be really practical for us programmers.
A short list of examples:
MD5-hashing / SHA-hashing
Quick lockup of unicode and HTML-codes for symbols
Color-codes
Please only include one search query per answer, then we can rate them to get the best ones to the top.
(I made this one a community-wiki, since we will be using the voting for ranking)
Note: If some of the links in the answers don't work (eg: wolfram doesn't find any results, then replace all + with spaces..
I might 'save time' by not playing around with it and doing real work instead. :)
Calculating lift coefficients of NACA profiles (example).
(I made a program for this, but it's nice to have the option to do it quick)
I probably won't use it for anything. I don't know about you, but I deal with enough black boxes on a daily basis, and I'd rather use the ones that have been tried and tested thoroughly.
This might come back to haunt me later, but it strikes me that although there might be a point to WA used in a mechanical manner, from my perspective I'm thinking it's not the hard calculable information questions which are the problem which needs to be solved, it's the soft human data which defies classification or rigid modelling. Google seem to understand this, not sure Stephen Wolfram does.
OTOH it could be that anyone can be Colin Laney now.
Someone double check me here:
The MD5 hash of "Wolfram Alpha" (no quotes) is:
882b 0be2 79eb 7e88 86cd 3dae 19c1 d267
And not:
a615 9984 9aee b7be 3091 68bc 0ab7 ?
EDIT: The hash changes every time given the same query...what kind of hash is this?
http://www14.wolframalpha.com/input/?i=MD5%22Wolfram+Alpha%22