SUN STUDY - DIFFERING RESULTS

[Gareth]

Here I have 3 different results for SketchUp (2014), the same thing rendered in Twilight, and then a rendered ArchiCad model.

The location, latitude, longitude, day and time were set exactly the same for SketchUp and ArchiCad

As you can see, there are 3 different results.

Which one can we trust ?

Some may think it is not significant, but when we apply a sun study to a building and the effect overshadowing may have on an adjacent site, the legal implications of getting it wrong could be very costly.

[Gareth]

UPDATE :

I have solved the problem with ArchiCad, and I can now get the same results as SketchUp. It turns out that ArchiCad's render engine has its own Sun settings which will provide a different result from ArchiCad's own internal Sun settings.

So, I can assume that SketchUp and ArchiCad a both correct.


The difference in TW is puzzling though. We had a similar issue in an earlier version.

[Chris]

In the Environmental Dialog, did you check "Corrected Shadows"? By default, the Twilight Render sun is much closer (and smaller) than a "real" sun. This produces better soft shadows but also introduces some parallax errors in shadow direction. Clicking "Corrected Shadows" pushes the sun out to a realistic position (and size) to produce better sun position but doesn't have as good soft shadows.

[Gareth]

Thank you Chris.

No I hadn't thought to check the 'Correct Shadows'. However, when I did, it made little or no difference.

In the meantime, I'll just adjust my settings by 30 minutes to make sure the render is the same as SketchUp.

When I get some spare time I'll delve into this further.

I have a theory (that could be dangerous eh ??) but I need to test it on a few examples first. I'll let you know what happens.

Cheers,

Gareth

[Fletch]

... check the 'Correct Shadows'. However, when I did, it made little or no difference...

that's unexpected.

Care to share the file for us to test? Is it far from the 0,0,0 origin of the world coordinates for SketchUp?

[Gareth]

... check the 'Correct Shadows'. However, when I did, it made little or no difference...

that's unexpected.

Care to share the file for us to test? Is it far from the 0,0,0 origin of the world coordinates for SketchUp?

I haven't kept the file for the above test....it was pretty quick though and I'll do another one shortly.

As for the 0,0,0 coordinates, frankly I cant remember, but I don't believe it was too far from it.