topic Re: View goTo target, looking for the best solution if there are many polygons and graphics. in ArcGIS JavaScript Maps SDK Questions

View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Wed, 28 Dec 2022 11:31:23 GMT

At a certain user's choice, I draw the necessary polygons at the given coordinates from the given object and add them to the map in the form of graph figures. Then I want to show the selection on the map and use method GOTO. Polygons are added in a loop. I've already tried all sorts of ways. And zoomed in. And changed in a cycle. And after the cycle. And in the end, it's still kind of clumsy. That's not in the right place. Either too small or too large. If, for example, the United States, then it is not in the middle at all. How best to use To zoom the user on the map to the right place? Is there a better optimal solution? Has anyone encountered similar problems?

my code is something like this :

const map = new Map({
ground: "world-elevation",
basemap: grayBasemap
});

const view = new SceneView({
container,
map: map,
qualityProfile: "high",
zoom: 4
});

this.view.graphics.removeAll();

for (var i = 0; i < objCoordinates.length; i++) {
var coordinates = objCoordinates[0];
var polygon = new Polygon();
polygon.addRing(coordinates);

var polygonGraphic = new Graphic({
geometry: polygon,
symbol: fillSymbol
});

this.view.graphics.add(polygonGraphic);
}

this.view.goTo({
target: this.view.graphics
}).catch(this.catchAbortError);

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Thu, 29 Dec 2022 13:22:51 GMT

I already see 441 views, but so no one could suggest anything?

Sadly. 😞

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Wed, 04 Jan 2023 19:16:52 GMT

I see the first line in your loop is:

var coordinates = objCoordinates[0];

This would definitely throw off your results, and I think you would rather intend:

var coordinates = objCoordinates[i];

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Thu, 05 Jan 2023 16:43:17 GMT

if (objGeoJSON.type == "Polygon") {
var coordinates = objCoordinates[0];
}
else {
var coordinates = objCoordinates[i][0];
}

No. It's not a mistake. I just didn't show all the code, because that's not the problem at all.

The problem is right here. When I add many countries. Or a lot of polygons. view GOTO to geometries or goto to all graphs don't work, as in this case. for example

this.view.goTo({
target: this.view.graphics
}).catch(this.catchAbortError);

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Thu, 05 Jan 2023 17:57:45 GMT

Regarding this code:

this.view.goTo({ target: this.view.graphics }).catch(this.catchAbortError);

this.view.graphics is a Collection, but the documentation for goTo does not specify that a Collection is supported. I would recommend passing a value specified in the documentation, like an array of Graphics:

this.view.goTo(this.view.graphics.toArray()).catch(this.catchAbortError);

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Thu, 05 Jan 2023 22:17:23 GMT

Thanks for your reply. Alas, but it does not help. I already tried both array of geometries and array of graphs. What I just did not do when there are a lot of polygons and graphs, it does not work correctly.

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Thu, 05 Jan 2023 23:46:41 GMT

At this point, I'd probably just recommend calculating the extent manually and zooming to that:

var extent = null; for (var i = 0; i < objCoordinates.length; i++) { //etc... if (extent === null) extent = polygon.extent.clone(); else extent.union(polygon.extent); } this.view.goTo(extent).catch(this.catchAbortError);

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Fri, 06 Jan 2023 10:59:24 GMT

Thank you very much again! It's nice to read a thinking person and understanding what he is talking about.

If I understood you correctly, then another idea is to collect not arrays of geometries or graphs, as a target, namely, to collect the sum of extent each polygon?

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Fri, 06 Jan 2023 14:01:19 GMT

Thanks. I tried it and this solution really looks much better in many cases. But there is one case and I attached files with a picture, where it is shown how I would like it to be in reality and for some reason how it turns out. I do not understand why it turns out away from the created polygons. For example, in the case where there are many multipolygons, as in the case of the USA and the islands around. There is no even understanding why this is so?

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Fri, 06 Jan 2023 18:11:17 GMT

It looks like in this case, the issue is because the full extent is crossing the international dateline. Therefore, a single extent object will have 'x' values that go beyond the boundaries of what's defined for the coordinate system. You may be able to solve this easily by using Extent.normalize. In that case, the final line would be:

this.view.goTo(extent.normalize()).catch(this.catchAbortError);

Although this post is from a completely different API, the images used in the post marked as a solution help to illustrate what you're seeing.

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Fri, 06 Jan 2023 20:25:24 GMT

I was so happy that there was finally a solution to this unsolvable problem. But unfortunately, everything is the same without changes. The problem hasn't been resolved.

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Fri, 06 Jan 2023 21:08:48 GMT

I wasn't certain that would work, but it was worth a try. In this case, I think you must fix the extent so that it starts on the left-hand side of the international dateline, and extends eastward across it. You should add this function somewhere in your code:

Then, you would change the call to goTo to be

this.view.goTo(fixExtent(extent)).catch(this.catchAbortError);

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Sat, 07 Jan 2023 10:49:21 GMT

Once again I want to thank you for your complicity in the problem and for your answers. Thank you! Here, from the documentation and the code, another question appeared. The documentation recommends, in a case similar to my code, to use extent clone. Although I do not really understand why and what it changes and gives in the end. But the question is this from the code.

if (extent === null)
extent = polygon.extent.clone();
else
extent.union(polygon.extent);

Why don't use clone everywhere? For example extent.union(polygon.extent);??

extent.union(polygon.extent.clone());

Could this have something to do with it and make some difference?

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Sat, 07 Jan 2023 17:00:38 GMT

Unfortunately, this did not help in solving the problem. Everything is exactly the same as it was before.

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Sat, 07 Jan 2023 17:32:01 GMT

I will also add that I get the length if (extents.length === 1) in any case all the time equal to 1.

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Mon, 09 Jan 2023 18:01:02 GMT

We should clone the extent because we plan to modify the values of that extent object, and we eliminate the potential of those changes causing problems for the owning polygon object. (In this particular case, it probably wouldn't matter, but it's just good practice.)

In the line:

extent.union(polygon.extent);

only "extent" is modified, not "polygon.extent", so there is no need to clone "polygon.extent".

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Mon, 09 Jan 2023 18:04:56 GMT

Ok, this makes it somewhat difficult, because the full width of the calculated extent is the full width of the coordinate system itself. The map therefore centers at the Prime Meridian.

Does your dataset include data throughout the world, or just the US and the Pacific?

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Wed, 11 Jan 2023 05:35:55 GMT

if (extent === null)
		extent = polygon.extent.clone();
	else
		extent.union(polygon.extent);

Interesting. Then how do you explain this line? extent = polygon.extent.clone();

This is not a polygon extent clone?

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

DimaY — Wed, 11 Jan 2023 05:43:47 GMT

In various situations and cases, I receive information about an object that comes to me in the form of objects, one of the objects is GeoJson, which has coordinates. All cases from any other regions of the world work quite well with zoom. And only this case, as I showed in the pictures when I wrote the topic. For some reason it does not rotate the globe and stops and does not zoom. I don't understand why at all.

Re: View goTo target, looking for the best solution if there are many polygons and graphics.

JoelBennett — Wed, 11 Jan 2023 16:21:51 GMT

As stated previously, "We should clone the extent because we plan to modify the values of that extent object". In the first pass of the loop, we clone the first polygon's extent, because in each subsequent pass, that object will be modified in place by the union function.