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Twilight Render "vs." Thea

Posted: Tue Jan 27, 2015 3:06 pm
by Turner
Hi everyone -

this isn't at all meant to start a debate; I own Thea Render and am considering Twilight.

Twilight is very fast. However, in rendering the same scene, I'm finding that Twilight is much faster/cleaner, but Thea is perhaps more accurate in terms of shadows?

I'm not at my computer right now but just set up a very quick small room with some large "obstacles" in it, and found that in Twilight, the light "fills" the space much more effectively, so that the parts in the back of the space seem to be a lot lighter than they should.

I can post a comparison tonight, but was wondering if anyone can advise what may be going on.


Re: Twilight Render "vs." Thea

Posted: Tue Jan 27, 2015 3:09 pm
by Fletch
Which render setting are you using in Twilight? Which render setting are you comparing it to in Thea? Are you 100 percent sure you have the same lighting in both scenes?

In Twilight V2 there is a feature found in the Plugins>TwilightV2 settings for "match SU Shadows" but this is only for matching the SU sun exactly. There's something quirky about SU's sun, and so we treat the sun one way in most situations, but when matching SU's sun excactly for certain architectural situations, then it's good to have the option available. But it sounds like in your case that the sun shadows is not what we are discussing.

Re: Twilight Render "vs." Thea

Posted: Tue Jan 27, 2015 3:20 pm
by Turner
Thanks for the quick reply!

You are correct - I'm not referring to sun shadows, rather shadows cast by ambient light.

As noted I'm not at the computer I use for this stuff, but I'm attaching the basic form. The back wall, behind the shapes, is the area I was referring to.

In each case (Twilight and Thea), I haven't changed any settings, and rendered from the same point of view. I'll post renders tonight.


Re: Twilight Render "vs." Thea

Posted: Tue Jan 27, 2015 8:57 pm
by Chris
There are so many differences between Thea and Twilight Render, it would be pretty much impossible to explain the why a difference might occur, especially with something as complicated as lighting an interior space. I think the only thing I can say is, does it give you the results you want and is the interface compatible with your workflow? That's the question I would ask anyone comparing any two render engines.

Re: Twilight Render "vs." Thea

Posted: Wed Jan 28, 2015 2:10 pm
by Turner
Hi Chris / all -

Ok, here are a few comparitive renders. Twilight was on default and Thea was default but set to Adaptive BSD, outdoor .

Basically, the shadowing is more pronounced in the Thea renders, with more apparent reflected light in the (much faster, e.g. 6 seconds vs. 18 seconds) Twilight renders. I'd like to get closer to the Thea renders in terms of color, shadow density, and contrast, but not sure how.

I tried adjusting sky brightness in case that's what was filling in the shape in the Twilight renders, but the contrast between light/dark adjusted accordingly so it didn't make much of a difference.

Also notice what appear to be something like "bright areas" in the Twilight renders, for example inside the "h" shape, and where surfaces meet the floor and each other.

Could be in the way the sky light is interpreted?
twilight-thea.jpg (231.02 KiB) Viewed 5155 times
twilight-thea-no-sun.jpg (229.66 KiB) Viewed 5155 times

Re: Twilight Render "vs." Thea

Posted: Wed Jan 28, 2015 4:44 pm
by Fletch
Again, please tell us which render setting you are comparing?

By Render Setting - this means which render "mode" you are using. Both Twilight and Thea are hybrid engines so this means you can render in biased or unbiased render modes.
In Twilight, Easy 1-7 are biased modes, Easy 8 is unbiased for exteriors, Easy 9 and 10 are unbiased for interiors.
similar settings can not really be achieved in Thea, but as close as you can get are using Thea biased or unbiased modes.
BSD settings in Thea are "Biased" while "TR1" is remotely comperable to Easy 9 and TR2 is comparable to Easy 10. But again, none of these is actually comparable because the engines are not the same.

It would be like comparing 2 v6 engines from 2 different car manufacturers, sure, they both move the car, but they are not the same engine.

I agree with Chris, choose the one that works best for your workflow. :hat:

Re: Twilight Render "vs." Thea

Posted: Wed Jan 28, 2015 5:04 pm
by Turner
Hi Fletch,

I'll have to look the settings up tonight; note that I changed the bare minimum in each; default everything for Twilight, and only changed to BSD for Thea.

Anyway - I also have to read the Twilight manual :) Is there one more comprehensive than the Quick Start Guide?

However, in the meantime - can you advise where the default "pink" sky color/light is coming from? The sky color was unchanged before rendering in Twilight (white).

thank you,

Re: Twilight Render "vs." Thea

Posted: Wed Jan 28, 2015 5:29 pm
by derei
Does Thea uses Biased rendering modes?
Because from what I can see, what you rendered in Twilight was on Biased, not on Progressive mode.
Try with Twilight setting Easy9, see then the difference.

Re: Twilight Render "vs." Thea

Posted: Wed Jan 28, 2015 6:02 pm
by Turner
Hi derei,

Yes, Thea uses both biased and progressive rendering. These were done with biased.

I'll try that other setting tonight.

Re: Twilight Render "vs." Thea

Posted: Wed Jan 28, 2015 7:45 pm
by derei
I made a small experiment with those two images: I made them grayscale (for TL image I had to artificially match the background with thea image).
Then I adjusted the levels and contrast, to see if I can bring both images in the same "area". And I could.
That tells me the illumination is the same in both renders. Only the post-processing made by each engine is different. TL seems to apply a bit more contrast. But that is a per user setting, not a render engine situation.

So, from my point of view, it is possible to achieve same result, just take care to the post-pro settings (exposure, gamma, etc)

P.S. The files are not perfectly matched... it was just for my personal curiosity... there are obvious differences. As I said, was just to check if the illumination is so different.