EDIT I now get the right layer from map, so the question now sums up to knowing if a layer A which contains curves, intersectects layer B which contains a surface which can be a circle or a polygon that was just drawn. I tried turf library's turf.intersect but I get "cyclic object reference" from that library.
And I am already looping through the curves seperaterly, to the question is now "Does a curve intersect with a shape.
Also tried: ol.extent.getIntersection(...) but it work only with extents wich are rectangle and therefore give very imprecise results.
I have a map and a layer that is built and added through
var layer = new ol.layer.Vector{(...)};
map.addLayer(layer);
And I add a layer through interaction, as shown in this example: http://openlayers.org/en/v3.6.0/examples/draw-features.html?q=draw
(We use the Circle selection.)
I would like to get he intersection between the lines in the fist layer and the shape (surface) drawn through interaction.
So far, I know that I can catch the event:
var draw = new ol.interaction.Draw{(...)};
draw.on('drawend', function(event){(...)};
But so far I have no clue on what information I can get from the event and how to match it with the layer.
Related
I need to create an outline of a 2d polygon (I do that by scaling the vertices along the average of the edge normal's).
But there is a problem when handling concave polygons because of the possible self intersections.
I've tried to fix those self intersections via the benley-ottmann algorithm and discarding the smallest part, but that doesn't preserve the original shape very well.
So I would like to know if there is a way that preserves the original shape better?
I would look into "polygon offsetting", the basic idea would be that for every vertex of the polygon you change that into a circle with a given radius, for every segment of the polygon you change that into a rectangle parallel to the original segment, and take the union of all resulting forms.
When preforming a cut action on a polygon with a polyline, some of the returned geometries are grouped while others are not?
I have a simple program where the user can create a polygon with a SketchViewModel. Then the user creates a polyline with a SketchViewModel. I then take the geometry from each sketch and preform a cut from the geometryEngine. I get an array of geometries from the cut and add them to the layer while removing the original polygon and polyline. I would expect to get each subdivided piece individually but for some reason some get grouped together as one geometry even if they're not connected.
//polylineLayer and polygonLayer are graphiclayers
//submit is a html button to call the execution
submit.addEventListener("click", function() {
//subDivisions is an Geometry[] for the produced geometries
//ex. one line through a circle polygon would produce
// two geometries of each half. (this works)
// anything more complicated starts having grouping issues
// (see pictures)
var subDivisions =
geometryEngine.cut(polygonLayer.graphics.getItemAt(0).geometry,
polylineLayer.graphics.getItemAt(0).geometry);
polygonLayer.removeAll();
polylineLayer.removeAll();
//show the number of subdivisions
alert("size: " + subDivisions.length);
// add created geometries to the graphiclayer
for (var i = 0; i < subDivisions.length; i++){
tempGraphic = new Graphic ({
geometry: subDivisions[i]
});
polygonLayer.graphics.add(tempGraphic,i);
}
});
(sorry for the links to photos I don't have 10 reputation to post photos and this is a very visual project/issue)
Open screen:
https://ibb.co/WDcgmSn
Draw first polygon:
https://ibb.co/wd6CDbV
Draw polyline to cut polygon:
https://ibb.co/BG32863
Expected subdivisions - 10 Actual - 7:
https://ibb.co/0VMsHGg
Some are split into individual polygons:
https://ibb.co/SKXCJR8
Others are not:
https://ibb.co/7WqNB9q
All broken up pieces:
https://ibb.co/Pr0smrw
Wish I could comment instead of just answer but hard to say with out code.
Basically you are getting multipart polygons, you need to break those up.
Use a split in your array to break up the multi-part polygons split("]],[[")
Simplify Polygons using a geometry service would be worth a shot too. (before and after cutting)
https://developers.arcgis.com/rest/services-reference/geometry-service.htm
I have a curved map of the US that I'm attempting to drop pins on. Right now, I'm just doing some math to find out how far they are from the highest part of the curve and map their height accordingly. Since this map has some states higher or lower than others, this doesn't quite work out. Some pins are floating in space, others are buried in the ground.
What I'd like to be able to do is start them all at a certain height and move them down until they collide with the map face, but I can't find any reliable documentation or SO answers about how to do collision detection in THREE.js.
Is there a better strategy? How can I get these pins to rest their points on this curved map?
I followed #TheJim01's advice and used a Raycaster at each marker's location, pointed it downwards and used the distance property of the first intersection to adjust the marker's Y position.
A few gotchas that I got a bit hung up on: It took me a while to realize I needed to use the marker's world position rather than it's local position since they are all children of the map object. Also, I had moved the map's position and rotation before creating the Raycaster so "downward" was no longer down. So I just set the markers before moving the map around.
const raycaster = new THREE.Raycaster();
markers.forEach(marker => {
raycaster.set(marker.getWorldPosition(), new THREE.Vector3(0, -1, 0).normalize());
let intersects = raycaster.intersectObjects([map]);
if(intersects.length) {
marker.position.y -= intersects[0].distance;
}
});
I am trying to draw polygons on a map, using OSM data downloaded. I have written a query that returns a list of polygons from the planet_osm_polygon table. It resturns the list as JSON objects. I am using gl.drawArrays(gl.LINESTRIP, 0, json_data_length) to draw the polygons. I have done the same for points- I have a list of points returned and I have been able to plot them using gl.POINTS.
The problem is, I want each of the polygons to be drawn separately, but I guess using LINE_STRIP is connecting one ending point of one polygon to the starting point of another polygon.
For example, I want civic center plaza and buchanan street in SFO to be separate polygons. But the polygons, after being drawn, are still connected to each other through one point. I want these two to be drawn as separate polygons. How do I do it?
I do not want to use any libraries. Just basic WebGL. My JavaScript code takes the lat-long coordinates from my osm database and converts into pixel coordinates to help plotting- see link: WebGL shader code (http://psousa.net/demos/webgl/) I am using this example and extending it.
If i understood correctly you want to draw 'borders' of multiple polygons not the filled polygon itself.
In order to draw seperate lines in a single draw call you should use gl.LINES mode instead of gl.LINESTRIP.
Lets say you have a quad which has points A,B,C,D and a triangle which has points X Y Z. If you want to use glDrawArrays command with GL_LINES mode , your vertex data should be submitted as
{A,B, B,C, C,D, D,A, X,Y, Y,Z, Z,X}
Following lines are drawn with this vertex data
Line from A to B
Line from B to C
Line from C to D
Line from D to A
Line from X to Y
Line from Y to Z
Line from Z to X
In order to eliminate duplicate vertex data you can also use glDrawElements with a proper index .
I'm letting the user click on two points on a sphere and I would then like to draw a line between the two points along the surface of the sphere (basically on the great circle). I've been able to get the coordinates of the two selected points and draw a QuadraticBezierCurve3 between the points, but I need to be using CubicBezierCurve3. The problem is is that I have no clue how to find the two control points.
Part of the issue is everything I find is for circular arcs and only deals with [x,y] coordinates (whereas I'm working with [x,y,z]). I found this other question which I used to get a somewhat-working solution using QuadraticBezierCurve3. I've found numerous other pages with math/code like this, this, and this, but I really just don't know what to apply. Something else I came across mentioned the tangents (to the selected points), their intersection, and their midpoints. But again, I'm unsure of how to do that in 3D space (since the tangent can go in more than one direction, i.e. a plane).
An example of my code: http://jsfiddle.net/GhB82/
To draw the line, I'm using:
function drawLine(point) {
var middle = [(pointA['x'] + pointB['x']) / 2, (pointA['y'] + pointB['y']) / 2, (pointA['z'] + pointB['z']) / 2];
var curve = new THREE.QuadraticBezierCurve3(new THREE.Vector3(pointA['x'], pointA['y'], pointA['z']), new THREE.Vector3(middle[0], middle[1], middle[2]), new THREE.Vector3(pointB['x'], pointB['y'], pointB['z']));
var path = new THREE.CurvePath();
path.add(curve);
var curveMaterial = new THREE.LineBasicMaterial({
color: 0xFF0000
});
curvedLine = new THREE.Line(path.createPointsGeometry(20), curveMaterial);
scene.add(curvedLine);
}
Where pointA and pointB are arrays containing the [x,y,z] coordinates of the selected points on the sphere. I need to change the QuadraticBezierCurve3 to CubicBezierCurve3, but again, I'm really at a loss on finding those control points.
I have a description on how to fit cubic curves to circular arcs over at http://pomax.github.io/bezierinfo/#circles_cubic, the 3D case is essentially the same in that you need to find out the (great) circular cross-section your two points form on the sphere, and then build the cubic Bezier section along that circle.
Downside: Unless your arc is less than or equal to roughly a quarter circle, one curve is not going to be enough, you'll need two or more. You can't actually model true circular curves with Bezier curves, so using cubic instead of quadratic just means you can approximate a longer arc segment before it starts to look horribly off.
So on a completely different solution note: if you have an arc command available, much better to use that than to roll your own (and if three.js doesn't support them, definitely worth filing a feature request for, I'd think)