VRay leaves...

[joconnell]

Yep morne And zeronove - that's the one.

[stevesideas]

How are you guys getting good results without sub pixel on. I get lots of sparkles on the leaves...

Update: I had a vray sun in my scene that was causing the sparkles...never mind

[tricky]

Good grief its a battle trying to get decent looking leaves, even with all the help on this forum. So many factors to consider. Chaosgroup - please sell us (me!) a library of tree leaf (not tea leaf) textures ready-to-go!?! haha!

[windowlicker]

Good grief its a battle trying to get decent looking leaves, even with all the help on this forum. So many factors to consider. Chaosgroup - please sell us (me!) a library of tree leaf (not tea leaf) textures ready-to-go!?! haha!

It would be so much easier with a 2sided material that's working as real life thin object translucency does. Any updates on this issue, Vlado?

I've managed to get decent looking leaves when using low translucency in the 2sidedmtl - between 64 to 96 RGB. You can always boost the lighting in post. As for the reflection, it can easily be boosted too. You only need to decide on the reflection glossiness. Also, using flat leaf planes will not look good. They need some curvature to look naturalistic.
But it's a good idea: Chaos Group should just bundle a whole bunch of nice materials and sell (give?) it to us faithful customers.

[snivlem]

In their SSS shaders, they have a few presets for Milk, Marble, Ketchup etc...I guess you'd just need a few basic presets - but why?

Leaves vary too much. The same tree one month will look totally different in another month. (Spring > Summer).

[vlado]

Any updates on this issue, Vlado?

Nope; many other fires to put out first. But even when it works, it will still behave in a very very similar way (only you'd see the textures from both sides), so there won't be much of a difference to the final result.

But it's a good idea: Chaos Group should just bundle a whole bunch of nice materials and sell (give?) it to us faithful customers.

That's an interesting question; and would you be willing to pay for them (if they are really quality materials with high-res textures)?

Best regards,
Vlado

[Morne]

That's an interesting question; and would you be willing to pay for them (if they are really quality materials with high-res textures)?

I just want to know why don't we have this in the 1st place?
Maybe if something like vray-materials.de was maintained and organised by ChaosGroup, there wont be so much junk floating around

[vlado]

I just want to know why don't we have this in the 1st place?

It's a matter of resources; someone has to take care of the whole system... we have discussed this internally many times, with the result that "it would be nice to do something" I hope that with the .vismat implementation, this would become a step closer to reality - we already have many .vismat files on our website.

Best regards,
Vlado

[windowlicker]

Nope; many other fires to put out first. But even when it works, it will still behave in a very very similar way (only you'd see the textures from both sides), so there won't be much of a difference to the final result.

Not sure about the "very very similar" part, seeing the texture from both sides would make a huge difference! If you will get the material to act like it does in real life, I'm sure making realistic leaves will be a piece of cake. Looking forward to it, whenever you get around to it.

As for buying materials and textures, I know we would. We buy a lot of stuff from different providers - as long as the quality is good. It's always a good investment buying assets as opposed to making them yourself.

[joconnell]

The only part of the problem though Morne, for example people are constantly asking for good settings for metal, and when you tell them to set up a grey reflection and make it slightly glossy they get upset when their renders look bad. Since the lighting and environment of the scene has such a massive effect on the look of a material there's no guarantees you'll get a good final result even if the materials were set up by someone that really knows vray.

It's also a bit of a chicken and egg situation when making materials from scratch. Do you tweak your light to suit the materials or the materials to suit the light? I'm doing a tonne of VFX stuff at the moment and one of the nice things is that done properly you take some grey and chrome ball reference of your lighting conditions. The shade of grey is a known RGB value so if you make a cg grey and chrome ball that match your reference shoot, it means that your lighting is very, very accurate. Then once you know your lighting is correct, you only have to tweak your materials so you've only one factor instead of two that constantly play off each other.

[vlado]

Not sure about the "very very similar" part, seeing the texture from both sides would make a huge difference!

Leaves are so small, that unless you are really close, the texture will not matter at all. And the overall effect from a distance will still be the same.

I agree that we should fix it, and we will, but I very much doubt that it will automagically make the leaves look better.

Best regards,
Vlado

[windowlicker]

I do think textures will matter a lot - especially if there's a big difference between front and back textures... as is the case for many trees. The 2sided material works reasonably well if you have the same back and front materials, but less well when they are different.

Oh, and by the way, would it be possible to get an option to use monochrome energy preservation mode for the translucency? Now, when I use a green color, I get a purple tint on the parts that are not backlit.

[trixian]

When it comes to shaders for this and that, I would gladly pay for them, as long as they are part of the total price, and not some "add-on" you purchase on the side.

More importantly though, I think these shaders should be as non specific as possible (I.E not a special shader for copper, aluminium etc), and should cater to those types of stuff we can't easily fake with the current shaders.
One thing that comes to mind is thin film plastics (gladpack and the sorts) where neither single sided shaders or sheets with incredibly thin thickness don't look right, or require long render times. So some sort of shader we can apply to one sided models that are tightly wrapped onto other surfaces but with "correct" refraction for example.

I'd also like a system of map nodes, like a curvature\cavity map, or a map similar to the "stress map" that Grant Adams made, but not through vertex colours like his.
Another node that would be usefull, is a "global material variance" node one could place on top of the material one uses to randomly vary certain parameters, so maybe the different 3rd party scatter systems could use a unified system for randomness\variance, ensuring we would not need to constantly worry about bugs, versions, missing features etc. for all these plugins.

One thing I would also love, would be a way to make shaders like in UDK, specifically the materials that blend through a "LERP" (linear interpolation) node. This would be great for painting variance in maps. (Would require math nodes im guessing). This should obviously be Autodesk's job to give us, as it is more like a 3dsmax feature, but we all know AD. I have no expectations for them any more.

Generally I would also request that the documentation of all maps and materials is properly filled out, with sane english explaining what the "parameter in question" does, and examples of it in action.
Docs now are rather lacking, and sometimes only repeat the parameters name in a sentance like "adjusts the fog bias" for the spinner called "fog bias" (I just made this one up on the fly, but you get the jist).

Just my 2 buckazoids

[windowlicker]

As I was googling on the topic of thin object refraction, I came across this article which is a breakdown of resarch done on the optics of leaves. http://www.photobiology.info/Jacq_Ustin.html It features several models for describing absorption and scattering, but the stochastic approach (section e), and particularly the "SLOP model" (figure 11) looks like it could be made into a shader fairly easily.

I made a sketch as a suggestion to how I figure it would work.



The SLOP model could be simplified, and instead of simulating scattering in different layers of the leaf, a single "Scatter" or "Mix" amount could be used, where 0 means there is no translucency in the material, and that 1 means equal amounts of the internal light is emitted on both sides of the material. I figure this is the maximum amount of translucency, since if more light is passing through than what is scattered back, the material would in fact be transparent. If that is needed, a Transparency amount could also be added as a separate map node.
The rendered diffuse component would be "backlit" by the interior light, which in turn is a mix of the total diffuse light and a color tint (to simulate chlorophyll), and possibly an Absorption factor, if that is needed.
I wonder if it would be useful to make the internal scattering fresnel controlled, since light incoming at a lower angle probably will scatter differently than light incoming at a perpendicular angle.

The benefits are several:
1. Specular (incl reflective) properties are left out the "scattering" and are therefore easy to control (and render?).
2. A large amount of translucency would be achieved, and the diffuse map would still be easy to correct if the rendered leaf is too dark or too light.
3. A tint component is added to easily change the color of the scattered light.

So, what do you say? Does it make sense? Would it be possible to turn this into a material that renders fairly quick? It shouldn't break energy conservation since it's based on actual observations and research, right?


As far as making leaves in the current version of vray, using the current version of the 2sided material, this is where I'm at.
It's basicly the same method as everyone else is using, with a front and a back material, mimicking the apparent looks of leaves caught in the wild (color, reflection and bump). I've taken the photos myself and color corrected them quite carefully for a neutral appearance. I'm using a translucency map, which is darker at the veins, and lighter at the thin part of the leaves. I'm comping that with a falloff map to get a bit of variation depending on the viewing angle. I'm keeping translucency at a fairly low amount as not to destroy the diffuse and specular aspect of the front facing material. I'm also using a quite carefully modeled leaf, to get more variation to the highlights.

Rendered with HDRi only.
Backlit, and with sun (and some color boost done in post).

[Pixelcon]

Beautiful images, windowlicker. Best yet.