polygon

问题 I'm trying to calculate 3D polygon's normal using Newell's approach. The problem I'm facing is that the value of z is always returned in positive even though the polygon is facing -z. However, when it's facing -z it also flips the values of x and y as well so if actual value of x is -x it'll be +x and same goes for the y. I can't figure out why that is happening. I hope someone can point out what I'm doing wrong. Here's what I wrote so far (using PHP): $verticies = [ [57.36, 30.98, 0.0], [52

问题 I am another rookie in iPhone programming and I have a very basic question which I can not answer. First of all, I am writing code in xcode 3.1.4, so that I can learn the basics on an old platform and hopefully in the near future this will allow me to create portable apps (in the sense that I will be supporting iPhone 3 as well). Unfortunately though, from what I understand, apple has stripped the documentation that came with xcode 3.1.4 and this makes it hard to guess what is the right way

问题 I have table metro_station: CREATE TABLE metro_station ( metro_station_id int(11) NOT NULL DEFAULT '0', metro_station_name varchar(25) NOT NULL DEFAULT '', lng double(12,8) NOT NULL DEFAULT '0.00000000', lat double(12,8) NOT NULL DEFAULT '0.00000000', PRIMARY KEY (metro_station_id), KEY metro_line_id (metro_line_id) ) INSERT INTO metro_station (metro_station_id, metro_station_name, lng, lat) VALUES (101, 'Name1', 27.53907013, 53.88590000), (102, 'Name2', 27.54864857, 53.89176877); AND Table

问题 I am trying to plot a polygon using a .json file. *EDIT to add sample coordinates { "type": "FeatureCollection", "features": [ { "type": "Feature", "geometry": { "type": "Polygon", "coordinates": [ [ [ -0.0691250297447329, 51.5462448874379 ], [ -0.0691510961928943, 51.5459630404703 ], [ -0.0692056531364391, 51.5456827414947 ], [ -0.0692883661627076, 51.5454050640766 ], [ -0.0693070134960316, 51.545356361588 ],..... The script looks like var width = 960; var height = 600; var svg = d3.select(

问题 So I am new at ST_ functions in MySql and I think that I am missing something. I am trying to save a POLYGON in MySql, the problem is that when using the function ST_GEOMFROMTEXT and giving the coordinates of the POLYGON taken from Google Maps Javascript API it returns the error: Invalid GIS data provided to function st_geometryfromtext . I've read a lot in Internet but everywhere it mostly says that it's a version problem, the thing here is the I have the most recent one right now (5.7.19)

问题 I'm creating polygons on a map getMap().addPolygon( getPolygonOptions(point1, point2, widthInMeters) .fillColor(Color.YELLOW)); The position of the corners is calculated by: public static PolygonOptions getPolygonOptions(LatLng point1, LatLng point2, double widthInMeters) { double distance = SphericalUtil.computeDistanceBetween(point1, point2) + 6; float bearing = location.getBearing(); double bears = bearing; LatLng corner1 = SphericalUtil.computeOffset(point2, widthInMeters / 2, bears + 90)

问题 I have multiple circles (as list of connected vertices) at random positions. When the circles intersect, closed areas are created (just like in a venn diagram http://en.wikipedia.org/wiki/Venn_diagram) How do I generate separate polygons of all of these areas? The goal would be to be able to color every region with a separate polygon like in this example: Is a general solution possible with iterative boolean intersection operations? EDIT The following simple snipped is a [NodeBox](http:/

问题 I have an OpenGL-related issue. Whenever I attempt to draw a simple polygon using four vertices from a vertex buffer... nothing happens. However, it will draw the shape in GL_TRIANGLES or GL_TRIANGLE_STRIP mode, albeit distorted. Am I doing something wrong? Relevent code: Vertex array: http://i.imgur.com/nEcbw.png GL_POLYGON: http://i.imgur.com/idfFT.png GL_TRIANGLES: http://imgur.com/84ey3,idfFT,nEcbw#0 GL_TRIANGLE_STRIP: http://i.imgur.com/JU3Zl.png 回答1: I'm using a forward-compatible 3.2

问题 I have a number of polygon images like a hexagon, a pentagon, any quadrilateral etc.. i need to generalize the detection technique to detect the RIGHT number of Corner coordinates.. no extra coordinates should be generated. for eg:- the code should detect only 4 for a quadrilateral, 3 for triangle, 5 for pentagon and so on.. I used HARRIS corner detection to detect right corners by specifying the number of corners value but i cant use the same code for an image with different number of edges.

问题 I have some points in database that make polygon on map. i am using Google Map Api v 3 . Now I am trying to add some area in polygon such as I would like to add 100m in every side of polygon and make new one on map along with the original. I tried that but it not make correctly. i add up my code here. Note 100m area is just example value Code $(function() { mapOptions = new Object(); mapOptions.zoom=19; mapOptions.center = new google.maps.LatLng(33.575802425924934, 73.14534723758698);