Author Topic: Sun & Sky: Which way is north?  (Read 4312 times)

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Offline Esben Oxholm

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Sun & Sky: Which way is north?
« on: January 27, 2016, 01:02:23 pm »
Hi guys.

I was wondering... when creating a sun & sky hdri it is possible to set the exact location, date and time, which is very useful for e.g. architectural daylight studies. The problem is... I don't know which of the hdri is pointing directly north.

Would be very useful to know, in order to position it correctly in relation to the building you are doing the daylight studies on.

Is it possible to find out the direction of north anyhow, or is it something that is planned to be implemented anytime? :)

Best,

Offline TpwUK

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Re: Sun & Sky: Which way is north?
« Reply #1 on: January 27, 2016, 01:23:06 pm »
You can set the location by clicking where it says custom there is a drop down box with major cities around the globe listed. If your location is not listed then you can Google the cities location. You can then adjust the time of the day, month etc. Then you just rotate the HDRi to suit  the direction you need.

Or have i mis-understood something ?

Martin

Offline Esben Oxholm

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Re: Sun & Sky: Which way is north?
« Reply #2 on: January 27, 2016, 01:38:33 pm »
You can set the location by clicking where it says custom there is a drop down box with major cities around the globe listed. If your location is not listed then you can Google the cities location. You can then adjust the time of the day, month etc. Then you just rotate the HDRi to suit  the direction you need.

The thing is that I don't want to rotate the HDRI to roughly suit my needs. I want the sun to point in the exact direction in relation to my model. Not sure if I'm being very clear...

For example, if I have a model of a house with a row of windows that I want to face directly south.
Then I want to create the sun at a given coordinate, at a given time, to see how the light enters my building.
When I have created the sun&sky HDRI I can rotate it, yes, but is there a way to exactly align the south of my model with the south of the HDRI?

The 'azimuth' and 'altitude' information inside the HDRI-editor caught my eye, and I figured that I could start with a date and time with an azimuth of 180 (which I believe is supposed to be south), and rotate my model according to that... With that in place, I should now be able to generate the HDRI for a different date and time, without changing the now correlated position towards south... but how is the shown azimuth and altitude calculated?
It doesn't fit with the information that I can find on the web... at least I have never seen the azimuth as a negative value before.

Is it a bug, or just another way to calculate the position of the sun?
« Last Edit: January 27, 2016, 01:42:59 pm by Esben Oxholm »

Offline TpwUK

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Re: Sun & Sky: Which way is north?
« Reply #3 on: January 27, 2016, 02:02:36 pm »
Ah - A conundrum indeed ... I could come up with some guesses but that's all they would be :/

Martin

Offline KeyShot

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Re: Sun & Sky: Which way is north?
« Reply #4 on: January 27, 2016, 03:12:56 pm »
In KeyShot 6.1 the x-axis is east, and the negative z-axis is north. We will add information in a future version to show more clearly where the poles are.