Can anyone explain how the new light settings in 2015 really work?

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12-22-2015 01:47 AM
timrobinson
New Contributor III

I don't really get the idea of setting up light for "month" and "time" without also having a "day" function....

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ThomasFuchs
Esri Regular Contributor

Hi Tim,

Thank you for your comprehensive feedback! Based on your insights I have created users stories for futher improving the feature.

I now understand that for your work, you need very high accuracy in shadow analysis. This means that the 3D models casting the shadows, also have to be very exact.

Please understand that for CityEngine there was a decision made to only offer moth accuracy. I know, that in order to be more accurate the day and even the year (leap year effects, precession and nutation of the earth, ...) need to be considered.

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ThomasFuchs
Esri Regular Contributor

Scene Light is defined by solar elevation and azimuth.
The most important factors to determine these values are:

  • Geo Location (long, lat)
  • Time (morning, noon, evening)
  • corresponding Time Zone
  • Month (on northern hemisphere June for max and December for min elevation)

For most analysis the shortest (June) and longest (December) shadows over the course of a day are relevant.
In this two months solar elevation and length of a day are not varying much from day to day.

So for simplification the exact day can be neglected.

timrobinson
New Contributor III

Hi Thomas,

Thanks for the advice on how this "works".

I've got to say this feature now seems pretty useless to me - I'm going to go back to using my old method of manually entering angles cribbed from an excel spreadsheet. I'm a bit disappointed in ESRI on this one - unfortunately it seems to show a lack of interest in using CE as a real-world design tool. The "interactive" tool in 2015 is not really any improvement....

I would offer several observations:

- the precision and trustworthiness of sun angles and times/dates in software models can be a legal issue in many countries as part of planning permissions/ consenting. Here in New Zealand this applies to shadowing of key public spaces which can be subject to very precise controls, and now also to some general residential area planning consents. Other software packages have been criticised over this, and I think it's fair to expect a vendor like ESRI to consider precision and reliability of time/day/daylight savings etc when offering features such as this. Deferring accurate shadows to post-export render environments is not an answer for iterative design investigations.

- the mid-season (Equinox) is just as important as the high and low seasons, and in this part of the year the shifts in sun angles are most exaggerated between beginning and end of a month. Not being able to precisely rely on sun angles to be the 21st of March or September is a real problem. Here in New Zealand the mid-seasons are key as they are the parts of the year which people begin to or stop occupying outdoor space as the solar pattern transitions.

- the interactive slider interface is the way to go, but without a day slider it really is pretty arbitrary. For building and urban designers, the ability to watch how shadow changes in a space over the course of a day / month/ year is very instructive and an important part of environmental design iteration. Sketchup is really great for this - I would strongly suggest that the shadow slider dialogue and lighting controls become something that can be docked to the edge of the screen so that its out of the way of the main view. I might be wrong, but my quick play with 2015 this week seemed to only offer this dialogue as a standalone box, and a chunky one at that.

I hope this feedback helps! Love the idea of this addition, but without more work it is a bit of an unusable feature.

Tim

ThomasFuchs
Esri Regular Contributor

Hi Tim,

Thank you for your comprehensive feedback! Based on your insights I have created users stories for futher improving the feature.

I now understand that for your work, you need very high accuracy in shadow analysis. This means that the 3D models casting the shadows, also have to be very exact.

Please understand that for CityEngine there was a decision made to only offer moth accuracy. I know, that in order to be more accurate the day and even the year (leap year effects, precession and nutation of the earth, ...) need to be considered.

View solution in original post

timrobinson
New Contributor III

Hi Thomas, thanks for listening! I included all that detail just to map out the challenge; if this type of feature makes it in that would be really great, but I do understand if it's not top of the list. Thanks again!

Tim

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