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Generate Buildings based on the Parcel Area percentage

royharb

Hi Matthias,

In our recent project I am working on, I was asked to create a rule where i can generate buildings based on the plot area.
For example, if i have a 500 avg parcel Area, I want my buildings to have 50 % of each plot and centered
within the available area and having a fully control over my setback.

Thank you,

Best,

Roy

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Accepted answers

NathanStocker

Oh I've actually worked this out. I got around the issue with separate branches by making a footprint, then saving the scope measurements and reverting the shape back to the original parcel, then doing the envelope.

I was previously trying to then shrink the envelope down to the footprint scope sizes, but the trick was instead to split it (both down the x and z axes) and only keep the middle bits, which were set to have the footprint sizes. I think it's perhaps more complicated to explain than it actually was, but I'm just glad it's all working now!

Thanks for the help.

Nathan

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DuliniRatnayake

Thank you Cheryl...

CherylLau

Maybe the splitArea function would be useful for your problem. It splits along a dimension according to a specified area (either specified as absolute or relative). Here is the help page:

splitArea Operation

However, this operation only splits in one direction at a time, so if you want to split in x and z, you'll have to split first in one direction and then split in the other.

DuliniRatnayake

Hi Nathan,

I am trying to do somewhat similar to your work you did couple of years ago.I cannot create the footprint based on lot coverage (as percentage of parcel).

Any advise high appreciated.

Thank you.

Dulini

NathanStocker

MatthiasBuehler1

Hi !

Well, one limitation of CGA is different 'branches' in the Model Hierarchy cannot query each other. When you branch off both Parcel Envelope and creation of footprint, those shapes have no more 'knowledge' of the existence of the other shapes.

Means there's not really a way to do this currently in CGA due to missing queries of this kind.

Options:
- Set an attribute for each building manually (well .. )
- Use some hack with occlusion queries. [ Though this is most probably going to give you more heachaches. ]

How many buildings to you need to 'design' this way ?

matt

NathanStocker

Hi Matt,

That's pretty much what I'm after - to extrude the building footprint to the roof of the larger envelope (which is based on the parcel).

Sorry for the confusion, when I wrote 'while the larger transparent one ignores it', I meant this it's based on the original parcel shape, not the building footprint.

MatthiasBuehler1

I'm not sure if I get the issue.

Are you trying to extrude the building up to the allowed height before it exits the envelope that's assigned on the parcel ?

What do you mean by 'while the larger transparent one ignores it' ?

m.

NathanStocker

Hi Matt, the screenshot attached has the process the rule follows, as well as an example of two envelopes. The pink/purple inner envelope is based on the building footprint, while the larger transparent one ignores it.

The solution would involve a third envelope which had the xz scope (footprint) of the pink and purple envelope and extruded out to the y scope (i.e. roof) of the outer transparent envelope at all points.

Nathan

Screenshot.jpg

MatthiasBuehler1

can you post a schema that shows the steps graphically ?

I wanna make sure I understand what you need ..

Matt

NathanStocker

It almost does. I was thinking of that, but then they would need to be reconciled, i.e. the envelope would need to be limited to the xz scope or the footprint would need extrapolated to the height of the envelope.

I thought that perhaps it required what you suggested but in a linear form, so I tried to:

Save the original scope values
create the limited footprint
save the modified x and z scopes
return the shape to the original x and z scope values
create the envelop
limit the envelope to the modified x and z scope values

This almost works, but the shape of the envelope carries through to the shrunken shape - it retains sloped sides where they could be straight up and down without breaching the original envelope. If I extruded the modified flat footprint very high and also created a suitable envelope, is there a way to extract the area which falls inside both shapes?

Oh and thanks for the help, it's much appreciated.

MatthiasBuehler1

Hi,

not sure, but it sounds that you need to copy your shape at some point.

like

A -->
    B. // is a copy of A
    C. // is a copy of A

Means you go like this:

Parcel -->
    DoEnvelope.
    GoAndSplitFootprint.

Does that make sense ?
Does this go in the right direction ?

m.

NathanStocker

Hi,

I have a similar issue, although I've resolved the site coverage part with:

Lot7 -->
case geometry.area > FootprintAllowed : s('0.99,0,'0.99) center(xz) Lot7
else : Lot8

Where FootprintAllowed comes from the site coverage % multiplied by the parcel size. All of which is borrowed from cityengine.blogspot.co.nz 🙂

The rule also needs to use an envelope operation and unfortunately I can't get it to work in co-ordination with the site coverage part.
At the moment (and in order), I apply yard restrictions, set the maximum building footprint (based on the site coverage operation above), determine the max height, and then create a building envelope.

My issue is that the envelope operation uses the building footprints for its boundaries, rather than the original parcel boundaries. I need it to use the predetermined building footprints, but to work out the envelope based on the parcel boundaries. I've tried putting the envelope operation first, but haven't been able to get it to work.

Any help would be very much appreciated!

Thanks
Nate

MatthiasBuehler1

Ok, but I need also a scheme on how the buildings are supposed to be placed on these parcels ..

Can you make an image ?

m.

royharb

Hi,

any shaped parcel and rectangular building footprint ?

that'd be easy .. 🙂

matt

Here's a small part of it.

Thanks Matt

Footprint.rar

MatthiasBuehler1

Hi,

any shaped parcel and rectangular building footprint ?

that'd be easy .. 🙂

matt

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