Translucency Woes :(

[spinner]

Hi,

I was wondering whether someone could help me?
I am not new to terragen, just new to some of it's new workings; I am currently struggling with making translucency work, or rather, I see it works fine, but not for me ;-)
Whatever I do, it seems as if I just get flat leaves, and now I am crying uncle.
I've tried:

* Just translucency in the default shader,
* Adding a lambert shader into the translucence function
* Used translucency in both shaders with different settings
* Sliding the sliders until my fingers were sore ;-)
* Rendering with and without GI/AO
* Tweaked settings in the specular tab

The tree is a testmesh generated in OnyxTree and I am using its default leaf textures. I know one way to "force" making it work, is to use a translucence image, but that really feels like cheating.
Enclosing image and node view. I've done better and worse renders, this is just the one I ended up with right now.
Grateful for any help :-)

Tree


Latest batch o' settings....


~s

[spinner]

Nevermind - I figured it - it was the reflectivity and a double translucence that made it look crap :-)

~s

[Hetzen]

Sorry Spinner, I was watching this thread with some interest, as I'm just getting to grips with translucency. Would you mind posting a render with your results?

[spinner]

Less is more, basically :-)

I turned off the AO for now, and reset the GI. It's not perfect, but it gives me a better tweakage baseline
I set the following in the leaft1 part shader:

Colour
* diffuse colour to 0.8
* colour image >Leaf Image.jpg
* colour function - blank

* Translucency 3.25, grey ( I tried a mossy green, but that didnt work so well)
* all the other ones downward, unchanged

Specular:

* Reflectivity, following Tangled Universe's advice, 0.2
* Reflection tint RGB 38,54,34 at 0,035
* Index of Refraction 1,5
* Specular Roughness at 0,45

Displacement:

* Unchanged, but added an image and am playing w parameters

Opacity
* Unchanged, but added an opacity image

Images:
- Unchanged

~s

[Mohawk20]

What I do is open the default shader of a tree object's leaf segment, and copy the diffuse colour map to the translucency settings and set translucency strength to about 0.8 (depending on the tree).

The basic working of translucency as explained by Matt is that the translucency function adds light to the side of an object that is not facing the sun. So it causes the shadow side of a leaf to be lighter. Now what you want to remember is this: translucency of 1 makes the shadow side exactly as bright as the sunlit side.

So any value over 1 is unrealistic, because then the shadow would be lighter than the light.
If you increase it to insane settings (like 100), the lightness of the shadow side will illuminate it's surroundings, resulting in weird, unrealistic, but very cool effects. Render time might increase though...


I hope that gives you more insight Hetzen.

[dandelO]

Plugging in a Lambert shader to the function input will have no effect, other than to apply full colour translucency of the colour specified in the lambert shader. A fractal, or imagemap function should be plugged in here.

The 'function' input only describes where the translucency will be visible, not the actual translucency properties - As the default shader already has a translucency value(set in the slider) to apply to itself, this will be applied via the 'function' you specify.

Using a different colour from white(but still bright) in the translucency fields will make the effect more apparent.
You're not advised(by Matt Faircough - TG mastermind) to set translucency beyond '1' in the input field but, I dispute this!

[spinner]

Thankee Sai, that helped explaining why it looked so crap. So you don't have to use lambert at all, unless I want light to scatter i.e via a power-fractal, or cheat with an image-map, yeah?

I'm used to Max' shader tree stuff, I am still learning the ropes on this in TG2, so thanks for the feedback :-)

It also seems as if translucency is a real bitch depending on what kind of leaf image one uses - I moved on to an oak, applied the settings above, and it looks fake again. ARGH !

~s

[spinner]

New question: Does TG2 do coloured or bw translucency maps?

~s

[Oshyan]

Black and white for all maps I reckon, unless you use the function nodes to manually split the channels out (I do believe that's possible).

- Oshyan

[spinner]

Thanks Oshyan :-)
I took a look at Gary Poole's tutorial, and that's just a plain b/w alpha? but a leaf is typically thicker in the middle, so how does TG2 handle the falloff - does it auto-add a gradient of sorts?

~s

[spinner]

this is what I mean by horribly flat.

I thought one translucency recipe would be a baseline recipe for all, but I am not so sure now.
I see I have translucency set up - the red in the leaves shows it's presence. But at the same time, I would have expected those leaves to "pop" a bit more, and maybe also show a bigger shift in hue, and to actually see some translucence.

As you can see, this is w a standard opening scene tg - do I need to crank up my lightsource to get a more translucent result? If so, how would one for instance handle translucence in morning or noon renders?

Again, thanks for all the help - I don't mean to be a pest, I just want to know how this works :-)

~s

[Oshyan]

TG2's handling of leaves and transparency is fairly simplistic right now, there's no accounting for a leaf being thicker in any part, etc. That could potentially be accounted for with the leaf transparency, alpha, and/or displacement map though.

As for your transparency/lighting issues, there are a couple things I would look at. First, soft shadows can have a big effect here, so if they're not on, I'd enable them. Sometimes the appearance of hard shadows makes the translucency effect much less evident. You can also try increasing the Global Illumination Strength on Surfaces to get more light in the interior of the tree. One other option to consider is increasing overall exposure. If you find some reference photos of what you're trying to achieve it would be helpful. In many cases of brighter foliage, any sky in the image is actually washed out because the image is exposed for the leaves. In your case it's more balanced, with the sky a normal blue, but also has a corresponding "flat" and dull look as a result.

- Oshyan

[spinner]

I'll try that, and thank you.
The effect I am looking for is right outside my window - a sunny summer morning in the wooded outskirts of Oslo :-)

Edit: I realised what I was looking for after a walk outside: Trees like i.e birches have leaves with a higher reflection-ratio, than i.e oaks and alders. As most of the woods here are evergreens and birches with a smattering of oaks and alders, I expected to see that higher rate of reflectivity on all leaves.
Also - the GI-tweak worked - the leaves now pop :-)

~s

[Matt]

New question: Does TG2 do coloured or bw translucency maps?

Wherever possible, image maps or functions are used as RGB multipliers. So feel free to use coloured translucency maps to get even richer translucency effects. But greyscale translucency maps work well enough in most cases if there is already some colour to the basic diffuse component.

Matt

[Walli]

I'll try that, and thank you.
The effect I am looking for is right outside my window - a sunny summer morning in the wooded outskirts of Oslo :-)

You must be careful, no regular display can reproduce what you see outside of your window - or mine ;-) Your eye is capable of adapting to brightness far, far better then any available display.
So of course its always good and important to look outside - but if you want to have a realistic render, then use a photograph as "final" reference. Photorealistic is not the same as realistic. We are mostly used to photorealistic, as we see photographs and movies all day long - and a render to be accepted as realistic usually has to mimic the "problems" of photography and filming.