Getting extruded building object about harp.gl HOT 2 CLOSED

Hi @gizm0bill, thanks for interest in our project.

TLDR, some parts of what you seek is possible but far from easy.

Problem 1.

Due to performance reasons, by default we don't keep any information about identity of map features, so what we see on map is just 3d geometry divided into tiles with no knowledge which polygon belongs to which "building" in your case.

To retrieve this information, you must at least tell OmvDataSource to gatherFeatureAttributes by setting it to true in constructor.
Note - this greatly increases memory usage.

See object picking examples: https://www.harp.gl/docs/master/examples/#object-picking.html

Problem 2

Due to already mentioned tiling, one "real" building may end up being split to several tiles and thus rendered by several distinct THREE.Objects.
So, we need to correlate "features" from many tiles and this is only available in some data providers.
Not all datasources provide feature id for all features.

Namely

• object picking example using https://xyz.api.here.com/tiles/herebase.02 shows that you don't have disctinct $id for each feature in this case
• XYZ OSM datasource https://xyz.api.here.com/tiles/osmbase/256/all- used in other example provides proper feature $ids AFAIR.

Problem 3

This is going hardcore as most of API is not documented as good as we would like to

Having gatherFeatureAttributes set, you can traverse scene and find all objects with userData.feature containing TileFeatureData objects to search for buffer geometry segments that are responsible for rendering feature by inspecting TileFeatureData.objInfos and correlating it with TileFeatureData.starts which tell where in particular BufferGeometry given feature starts.

Knowing ranges, you can use multi material/groups feature of THREE.Mesh to render selected ranges with other material - i would start with different color.

Problem 4

I'm not certain if we generate usable texture coordinates buffer.

Summarizing this part of this can be done, but require very intimate knowledge of engine.
Unfortunately we don't have ready any ready example to be shown at hand.

Hope that it helps, we're open to questions.

from harp.gl.

Much appreciated!

from harp.gl.