topic Re: "edgeattr array" new feature, sampling the streetWidth for streetfacing lots in ArcGIS CityEngine Questions

"edgeattr array" new feature, sampling the streetWidth for streetfacing lots

AbeleGiandoso — Sat, 13 Jun 2020 15:13:46 GMT

Hi all

Say you have a lot which you have subdivided in several minilots using CGA attributes.

All minilots belong to the same shape. All minilots are extruded upward and their vertical facades are separated with split comp.

Is it possible to use the new function edgeAttr.getFloat(attributeName) to sample the streetWidth Object Attribute of each miniLot facade?

To add extra complexity, all the streets are curved, not straight, so there are not 1 single street value per side, but several.

Simon Haegler , Cheryl Lau, any idea?

Thanks

Re: "edgeattr array" new feature, sampling the streetWidth for streetfacing lots

MatthiasBuehler3 — Tue, 16 Jun 2020 11:18:59 GMT

Hi there,

Shapes generated via CGA cannot sample other values on a per-leaf basis. Means you'll get one initial attribute that will be constant for all the shape (and it's successor shapes you create via CGA.

Cheers,

matt

matthias buehler | founder & CTO | msc arch eth zurich

Re: "edgeattr array" new feature, sampling the streetWidth for streetfacing lots

CherylLau — Sat, 11 Dec 2021 14:22:37 GMT

If you have lots that are not dynamic (i.e. not generated automatically by street networks) and streets in the scene, then it is possible to use edge attributes to sample street widths.

To mimic your case, I created a lot with 4 buildings on it.

Lot -->
	split(x) { ~cell_size: split(z) { ~cell_size: Cell }* }*

Cell -->
	offset(-offset_dist, inside)
	extrude(10)
	Mass‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

The lot is surrounded by streets with widths as indicated in the (last) screenshot below. Select the lot, go to Shapes -> Compute Edge Attributes. This will create object attributes with the prefix /edgeattr/. Streetwidths are calculated based on the streets near the shape.

Compute edge attributes tool—ArcGIS CityEngine Resources | Documentation

This code samples the edge attribute streetwidths for each side of each building and resizes the facade according to the sampled value.

Mass -->
	comp(f) { side: Side }
	
Side -->
	s('1, edgeAttr.getFloat("streetwidths"), '1)
	set(material.opacity, 0.5)‍‍‍‍‍‍

Sampling happens by projecting the current shape geometry onto the outline of the initial shape. Note that in your case with curvy streets where a building side might correspond to multiple streets, the function will only sample one of the streets.

edgeAttr functions—ArcGIS CityEngine Resources | Documentation

Re: "edgeattr array" new feature, sampling the streetWidth for streetfacing lots

AbeleGiandoso — Wed, 17 Jun 2020 15:15:20 GMT

Hi Cheryl

Thanks! Makes sense now.

So if I understand correctly these attributes are only created when Lots are not dynamic then and there is no way to do a similar thing for Dynamic lots, correct? To query the streetWidth list of a dynamic shape.

Re: "edgeattr array" new feature, sampling the streetWidth for streetfacing lots

CherylLau — Fri, 19 Jun 2020 11:40:47 GMT

Shapes -> Compute Edge Attributes can only be done on shapes that are not dynamic.

The streetWidth attribute can be used for dynamic lot shapes that are automatically created by street networks. However, note that this attribute is different than the edge attribute /edgeattr/streetwidths that is calculated for non-dynamic shapes. The streetWidth attribute does not include sidewalk widths, and it does not project to the nearest street (lot sides not touching a street get 0).