UK Spring

Started by efflux, March 29, 2008, 12:13:12 pm

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efflux


Oshyan

Actually, rather than increasing sunlight strength, you might try increasing exposure (which more directly matches how you would use a real camera to work with a scene that has a bright sky). You should then get correctly exposed ground and brighter sky (a lot of people aim for a middleground in TG2 work with a dark-ish ground and well-exposed sky). You can use an EXR to correct in post if necessary. Photomatix makes it easy, Photoshop also does fairly well, though Cinepaint may have more functions to work with as it's dedicated to high dynamic range image adjustment.

- Oshyan

efflux

March 31, 2008, 02:01:22 pm #17 Last Edit: March 31, 2008, 02:10:31 pm by efflux
Hi Oshyan.

I've yet to go into TG2 to experiment with this idea. However if you think about exposure with photography it never alone nicely fixes a high contrast between sky and ground or at least not usually. It depends where the sun is as you shoot. Many shots have other things used. First, a polarizing filter and then often some form of post.

It's just theory at the moment but I think there is a tendency to make TG2 scene to render exposed evenly but this could possibly result is dimness so I'm thinking of making a scene that has the real problems you'd have taking a photo. For example in a TG2 world, if you decide to change a shot to sunset then you'll usually have to bring the sunlight strength up. Maybe it wasn't bright enough in the first place?

Anyway here's some extreme post on a TG2 image. Sharpening done in Gimp. Probably too much but I'll eventually get a nice balance:



The original. I say original but this not like the original. It's another shoddy jpg downsize at Renderosity:

http://www.renderosity.com/mod/gallery/media/folder_157/file_1562413.jpg

There is a lot of jaggedness in my TG2 render outputs. I need to work on that.

Here is a screenshot of Lightzone with that image being post processed:



You see the selections. You've got polygon, spline and bezier to choose from. Then the inner zone is the line of where "feathering" reaches. You just drag that about as well. You can also select colours within those selection areas for more specific processing. When you go into another app it seems like a total pain in the ass. On the left you see various styles that you can save. The thumbnail shows instant feedback of the style as you hover over it. On the right in the processing stack you see a zone mapper open. The thumbnail above gives visual feedback of each zone as you move the mouse up through the zones then when you find the correct zone you just drag it. There are a lot of other tools. Relight for example which does what it says. This is of course the Linux version running in Ubuntu  :-*

It's free at present but I expect Lightcrafts will eventually charge. I bought a Mac license anyway. It's not system specific.


efflux

He he. I need to stop now before I start firing up TG2. I was messing around with this yesterday and forgot that the clocks had changed here. I ended up an hour late for work  :D

Oshyan

Lightzone looks extremely cool!

In regards to TG2 and exposure, I was not suggesting that adjusting exposure alone would be able to compensate for differences in brightness between land and sky. Rather that using exposure *instead* of sun power adjustments would be a more "realistic" or real world analogue, since you can't of course adjust the sun in the real world. ;D You are then left with the same problems as the real world which can be solved in the same way. In other words if you have an existing real-world workflow that solves those problems, either through HDR post processing, or some other approach, then you could apply it to the TG2 image in the same way. Once you start messing about with changing sun strength, etc. those techniques go out the window because they're based around a real-world exposure range. In your example with the sunset, instead of increasing sun strength you could increase exposure, then do a tone mapping from an HDR (EXR) output, for instance.

Not to say that adjusting sun strength and other TG2-specific approaches aren't valid - they certainly are. But if you're trying for strict realism or at least that realistic feel of light I think you'll have an easier time achieving it by sticking to what's possible in the real world (e.g. exposure compensation).

- Oshyan

efflux

Yeah, I understand what you mean about the exposure Oshyan. I'm also thinking about the contrasts. If the sun is turned up then in theory there should be more contrast between the lit areas and shadows even if underexposed. I'm thinking this would create a more realistic world because I'm convinced there is a lack of this kind of contrast in TG2 renders. The global illumination makes for even less contrast. I can see it in many of my renders except where the sun is brighter. You could use various tweaks in TG2 to compensate all this (probably what everyone is doing) but I'm thinking of experimenting with treating it like I was taking a photo with problems that need to be resolved in post. I think that if you say open a default scene and start working on everything then you will be adjusting everything to look good with that sunlight strength rather than adjusting the sun then everything else. I know this to be the case from Mojoworld. You design the planet then decide you want the sun turned up for a brighter look but all your colours and everything were designed with the lower sun setting.

If you think about reality, the sun is very very bright. If you look at a landscape with bright sky then your eyes mask the brightness so you can see into shadows as well. Of course a camera can't do this so that's when polarizing filters, post work etc comes in. When you look away from brightness it takes your eyes a bit of time to readjust from the extremes. I'm just thinking of trying to make renders look like a photograph even with it's inherent problems.

As for Lightzone. I love this app (apart from a bug in the Linux version - colour selection luminosity doesn't work). Cropping also has a few minor issues connected with the downsizing. Downsizing the image  never downsizes to exactly the resolution you want but these are side issues. I do downsizing in another app.

I think these companies have a hard task because of industry standard apps like Photoshop so it's not easy to break into the market even if their app is superb. That's why I mention Lightzone a lot. Definitely worth trying. I want to see them succeed.

Oshyan

There is a simple contrast adjustment in TG2 if contrast is what you want. ;D My point is that to treat it like a photograph you have to *not* adjust the sun, because that's not possible in the real world. In theory the TG2 default sun strength is similar to the real world, so adjusting exposure or contrast is a more photo-analogue method of working IMO. But as I said there are many approaches and all are legitimate. It's just a matter of what is most comfortable and effective for each person.

- Oshyan

efflux

I think there is a difference though Oshyan, because the contrast adjustment in TG2 will contrast adjust the whole render whereas a brighter sun will effect clouds etc in a different way that will not simply be a contrast change across the render. Clouds will blow out much brighter across the sky and light is going to be reflected round. I think these issues become much more interesting now that the apps have moved on with global illumination and glowing atmospheres etc. I dispute that the sun is similar to the real world in the default. If you open TG2 at default then move the camera to look at the sun it's not really very bright at least not like looking at the real sun (of course the comparison is a bit flawed since were looking at at a computer monitor here - not quite as bright as the sun) but I think it's set to get you a render that is fairly evenly exposed without a too bright atmosphere. If you try the default looking into the sun but turn it up by 0.5 to 4 then it looks a bit brighter and looks brighter if you take in down to the horizon. However that small change in setting becomes a lot more apparent on your ground lighting when you start really building the scene with hills, clouds etc.

My idea is to actually not change the sun strength for a planet once it's set so that when you move the sun around you don't decide it needs more strength for say a sunset.

Oshyan

I think your approach is fair. If TG2's default sun is *not* a real-world equivalent, I think it should be. People are much more used to working with photography than anything. This would of course be more effective if the camera controls (aside position, e.g. exposure, zoom) were more immediately accessible like a real camera, rather than having to go to the Camera node to adjust.

- Oshyan

Matt

March 31, 2008, 05:54:33 pm #24 Last Edit: March 31, 2008, 05:57:09 pm by Matt
Oshyan, Efflux,

If your TG2 scene uses only one sunlight and an Enviro Light set to Global Illumination mode, then adjusting the sunlight strength has the same effect as adjusting the exposure. This is because global illumination derives entirely from light that comes from the sun and then bounces/scatters around the scene a few times. In this scenario a change to sunlight strength affects everything but the balance between sky and ground, sunlight and shadow, remain the same. This is how it would be in the real world if you were able to artificially change the sunlight intensity and attempt to photograph it.

If you use other light sources, or use some of the ambient tweaks in the atmosphere, or use the Enviro Light in Ambient Occlusion mode, then they will be independent from the sunlight strength, so changing the sunlight strength would change the balance between sunlight and shadow, or sky and ground.

If in doubt, adjust the thing you actually want to adjust :)

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Oshyan

Good info Matt, thanks for the clarifications. :)

- Oshyan

Matt

March 31, 2008, 06:22:11 pm #26 Last Edit: March 31, 2008, 06:42:03 pm by Matt
Efflux, I think you're right about needing more contrast. To be more realistic, most scenes need terrain and vegetation textures to pretty dark relative to clouds or haze. Ground textures are usually surprisingly dark, and only bright in a photo because of the choice of exposure.

The defaults in TG are something of a compromise between how I'd like them to be and how most people expect them to be... at least until they start thinking about light intensity and exposure... :)

A big problem is the range of types of scene that need to be rendered. Snow is so bright that TG2's default sunlight and exposure are already too bright. Some deserts can have pretty high albedo too, so you can't really generalise about how bright terrain textures should be. But on the other end of the scale you have forests which are extremely dark, and for these you need to really crank up the light levels.

I'd like to make the default sunlight much brighter, but I think that can only happen when TG's interface has some particular enhancements which we haven't made yet. I would like to provide colour editing tools that make it easier to define dark surface colours which look right when lit by bright sunlight, and exposure controls should be considered throughout the user interface. The user shouldn't need to navigate to the camera or sunlight settings to experiment with different light intensities. But it seems like you've already made the necessary leap :)

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Matt

BTW, I know that some people reading this will be thinking something like "hey, but you live in England where it's always foggy. Sky doesn't look like that where I live."  But overcast skies reveal so much about how dark most ground and vegetation textures actually are, whether or not you're rendering an overcast sky. And it's been a while since I've seen any fog ;)

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Harvey Birdman

Quote from: Matt on March 31, 2008, 06:34:57 pm
BTW, I know that some people reading this will be thinking something like "hey, but you live in England where it's always foggy. Sky doesn't look like that where I live."  But overcast skies reveal so much about how dark most ground and vegetation textures actually are, whether or not you're rendering an overcast sky. And it's been a while since I've seen any fog ;)

Matt




Nope. Not me. Swear to god, I wasn't thinking that. Honest.

;D   ;D

Matt

Quote from: efflux on March 31, 2008, 04:29:31 pm
My idea is to actually not change the sun strength for a planet once it's set so that when you move the sun around you don't decide it needs more strength for say a sunset.


I think you might be imposing an unnecessary restriction there. In photography you would have no qualms adjusting your exposure to suit the picture, and you should do the same with a sunset in TG.

Matt
Just because milk is white doesn't mean that clouds are made of milk.