Sun angles/intensity

T

toaster_oven

0
Sun angles/intensity

hi-

does anyone have any suggestions/resources for figuring out accurate sun altitude/azimuth and intensity based on cheetah's light settings? I have azimuth tables to work off of, but am having a little trouble translating it to C3D. it would also be nice to know if there is any technique or resource for knowing the color spectrum and intensity for different times of the day at different locations. Right now I feel like there is an awful lot of guesswork in light settings, and I would either like some table to work off of, or have it built into the application...

Martin, maybe in a future release you could add in an option for selecting the time of day and locations (longitude and latitude) and allow the sun to be set that way in addition to the existing settings? I think it's a pretty simple and reliable formula...

-to
 
Toaster --

This has come up before, and I'm pretty sure it's on Martin's To Do list. I'd really like this feature too.

I'm sure in the meantime someone could implement it using scripting?
 
Hi,
yes atmosphere rendering is on my todo list. But I'm not sure yet when I find the time.

There exist some papers in the web which describe how to calculate the sun position based on time and global position. Writing a script and positioning a light source according to the calculated position should be possible.

toaster_oven if you search such a paper I can mail it to you. I think I have it somewhere on my HD.

Bye,
Martin
 
[perhaps OffTopic]

My experience in the field of architecture is that images must lie. At the beginning, in the early 90s, I pretended maximum fidelity to reality. Then I realized that the more photorealism I achieved, the worst it was if compared with watercolors, pencils, etc... With the time you learn the only goal is to express your project in the most expressive and beautiful way as possible... if you have to lie to achieve it, lie.

So, I put the Sun wherever shadows are better for my goal. Yes, even if I put the Sun in an impossible position it will never reach.

I am an architect, and I know architecture is just the art of lies :D (the architect often hates to lie -I hate to lie-, but however, the people you work for loves lies, so you lie because that's what sells)

The only exception is lighting design... But Cheetah3D doesn't work with Physics lighting units, nor has IsoLux display, so it can't be used for lighting design projects (at least not for the projects documents).

[/perhaps Offtopic]
 
shadow studies

Most 3d packages in placing the sun are quite accurate (archicad).

I did a study where i modelled up a physical site from a CAD survey, placed the sun, location, time (daylight savings) and date.

We took a digital photo from the same camera location with the same time and date data.

The shadows matched the photos within 98%.

I am also an architect, I agree re-creating real light will never be 100%. However for the pruposes of cheetah and locating the sun, these functions will be very helpful for work-flow for photomontage work and shadow studies (still and animated).

ian

p.s. Not all architects lie, they only lie when they don't understand the full process. ;)
 
mailman said:
The shadows matched the photos within 98%.
Click to expand...

Hi,
if you know your exact position on earth and the time there exists a formula to calculate the position of the sun. You can find the formula in that paper:

sunsky.pdf

But I don't know how exact this formula is. Maybe it contains some approximations. But 98% sound quite good to me.

Bye,
Martin
 
mailman said:
p.s. Not all architects lie, they only lie when they don't understand the full process. ;)
Click to expand...
I disagree. All architects in History lied (the most famous, the greatest liars :D ) (although of course I don't wish any flamewars)
Anyway, it's enough to read any architecture magazine or book... when you're at the second paragraph, you soon realize that the writer either 1)lies or 2)is hidding a part of the truth (which should also be considered as a lie).
But don't be too sad... Architecture is not the only profession that does it... think of marketing, publicity, politicians, filmmakers, etc... :D

Regarding lighting design, I meant physical simulation (using IES data for lamps, or similar). When you're doing lighting design, it doesn't make sense to lie. But when you're showing your project, the idea comes first than the reality (I don't say that I like it, but that's how it works in magazines, schools, contests, and the "V.I.P. world of architecture").
 
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