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.
Related
I'm trying to make a C++ OpenGL representation of our Solar System as a way to teach myself OpenGL, so please keep your answers simple.
The problem I have is that planets are very far away, so everything else is beyond the clipping plane when viewing from any given planet. How do I move the clipping of C++ OpenGL 3.1 plane to, say, 2000000000? I'd prefer a simple code snippet if you can.
I've looked up SO and forum posts about this, but they're either so old that nothing applies (using legacy APIs or just dead links), or so complex that I can't work out what they're saying.
Clipping planes are defined by the perspective projection matrix.
If you use glFrustum, change the last argument passed to it to 2000000000.0.
If you use your own matrix, set 10th element of your matrix array to:
(2000000000.0+nearClippingPlane)/(nearClippingPlane-2000000000.0)
(the formula is (far+near)/(near-far))
and 14th to:
(-4000000000.0*nearClippingPlane)/(2000000000.0-nearClippingPlane)
(the formula is (-2.0*near*far)/(far-near))
2000000000 is very big value, however, so Z-fighting may occur if you add details such as mountains.
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 :)
I got a huge problem. I'm stuck there for two weeks now.
It's seems pretty simple.
I'm creating a plane, mapping a texture to it.
After that I bend it, using the bend modifier from as3dmod.
Of course the plane got smaller after the bending process.
I've tried to calculate the first and last vertices.
var sizeAfterBending:Number = (-1 * plane.geometry.vertices[0].x) + (plane.geometry.vertices[plane.geometry.vertices.length-1].x);
I calculate -1 cause the first vertex is always negative.
The result of that is, if the plane is 400*533 it working fine.
But with a plane of let's say 640*480 it's not.
I'm missing something. It's really driving me crazy.
Does anybody has any idea?
Thanks in advance.
Cheers, MisterDan
JFY, I solved it.
I was trying to access this information before the rendering was finish.
Of course that's not gonna work ;)
Cheers, MisterDan
Does anybody know how to or where I can find info related on how to do a procedural skydome? Any help is welcome.
See this thread from GameDev. There's some example code in C++ in there too.
A skydome is simply a sphere, drawn around the entire level. Just draw a sphere, make sure back face culling is off, and front face culling is on (since you're inside the sphere).
To procedurally generate a sphere is trivial, my usual approach is to start with a hardcoded Icosahedron and subdivide the faces until the required detail is reached. There is a thread on gamedev about generating a sphere:
http://www.gamedev.net/community/forums/topic.asp?topic_id=537269
I'm not sure that really answers your question, seeing your response to the other answer makes me think there is some confusion about what a skydome is. To reiterate it's just a sphere, the important bit is the texture you draw on it.
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.