I'm learning about the theory of the projective plane. Very generally speaking, it is an extension of the plane, which includes additional points which are defined as the intersection points of two parallel lines. In the projective plane, every two lines have an interesection point. Whether they're parallel or not. Every point in the pro...
Hi, In one of our databases, there is a table with dozens of columns, one of which is a geometry column. I want to SELECT rows from the table, with the geometry transformed to another SRID. I want to use something like: `SELECT *` in order to avoid: SELECT col_a, col_b, col_c, col_d, col_e, col_f, col_g, col_h, transform(t...
Hello, I am finishing my thesis and have a large appendix. Some tables only look good, if first done on a3 and then (paper)printed on a4. Anyhow, working all the files seperalty is fine, but I struggle to compile all in one. I use the geometry package and start the document with: \usepackage[a4paper,left=30mm,right=20mm,top=20mm, bott...
Hello, How could I, having a path defined by several points that are not in a uniform distance from each other, redefine along the same path the same number of points but with a uniform distance. I'm trying to do this in Objective-C with NSArrays of CGPoints but so far I haven't had any luck with this. Thank you for any help. EDIT I wa...
The ellipse is actually a circle. I know all the coordinates of both things, I just need to know whether or not a line goes through an ellipse. Is this built in anywhere? SPecifically I am using QGraphicsEllipseIem and QLine but i can convert them to any other type thanks ...
Hey, I am currently designing an RTS Game in XNA. So far I have a Terrain Model generated from a Heigthmap and some Units that are drawn on it. The next step would be to give the units commands on where to move. To do that I have to calculate the exact position of the terrain behind the cursor when it's clicked. For Units selection I ...
I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is...
I have some simple javascript that determines where a click happens within a browser here: var clickDoc = (document.documentElement != undefined && document.documentElement.clientHeight != 0) ? document.documentElement : document.body; var x = evt.clientX; var y = evt.clientY; var w = clickDoc.clientWidth != undefined ? ...
I'm trying to create a very specific geodesic tessellation, but I can't find anything online about it. It is normal to subdivide the triangles of an icosahedron into triangle patches and project them onto the sphere. However, I noticed an animated GIF on the Wikipedia entry for Geodesic Domes that appears not to follow this scheme. Geod...
I have the lat/lon of 2 points on the earth. They are really close together, <10m. Let's assume the earth is flat. How do I calculate the distance between them in metres? I know about tools (PostGIS, etc.) that can do this correctly, however I'm just doing a rough and ready type, and I'm OK with low accuracy. At such small sizes a diffe...
How can I calculate the minimum distance between two rectangles? It is easy for rectangles which have no angles(0 degrees) but for rotated rectangles with any different angles I do not know how to do it.. Do you recommend any way? WhiteFlare ...
I have a toroidal-ish Euclidean-ish map. That is the surface is a flat, Euclidean rectangle, but when a point moves to the right boundary, it will appear at the left boundary (at the same y value), given by x_new = x_old % width Basically, points are plotted based on: * see edit (x_new, y_new) = ( x_old % width, y_old % height) Thin...
Hello, I have the following problem, I am trying to find the following distances (F1 and F2): This is what I have as of now: def FindArrow(self, X1, Y1, X2, Y2, X3, Y3): self.X1 = float(X1) self.Y1 = float(Y1) self.X2 = float(X2) self.Y2 = float(Y2) self.X3 = float(X3) self.Y3 = float(Y3) #center coords of...
Hi! I have to be able to set a random location for a waypoint for a flight sim. The maths challenge is straightforward: "To find a single random location within a quadrangle, where there's an equal chance of the point being at any location." Visually like this: An example ABCD quadrangle is: A:[21417.78 37105.97] B:[38197.32...
hi everybody, i'm working on google maps in specifically on geometry controls the point is, in this example when I click in line or polygon infowindow show up, but the language is english (by default I think) can I change the language? in the tooltips i can replace the text, but in this particular case i have no place do replace it, t...
How do I determine if a point is inside or outside a polygon that lies on the the surface of the earth? The inside of the polygon can be determined via the right hand rule, ie. the inside of the polygon is on your right hand side when you walk around the polygon. The polygon may Circle either pole Cross the 180 longitude Cover more...
There's a line A-B and C at the center between A and B. It forms a circle as in the figure. If we assume A-B line as a diameter of the circle and then C is it's center. My problem is I have no idea how to draw another three lines (in blue) each 45 degree away from AC or AB. No, this is not a homework, it's part of my complex geometry in ...
The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop t...
I need to compute the area of the region of overlap between two triangles in the 2D plane. Oddly, I have written up code for the triangle-circle problem, and that works quite well and robustly, but I have trouble with the triangle-triangle problem. I already first check to see if one entirely contains the other, or if the other contains...
Is there a way to geometrically compute the intersection points of a line and an arbitrary graphics path? I know where all of the lines and curves are in the path, and I am using the HTML5 canvas element if that helps any. Basically, I have access to all of the canvas drawing commands and their arguments. For instance, if the API was c...