Basically everyone there is trying to create realistic, but as efficient as possible foliage. In terms of efficiency I’m talking viewport/ram efficiency, nobody there seems to care too much about render times.
Any ideas?
My thinking is that the 2sided material is probably the way to go, as SSS requires a closed volume in which to scatter light - and when we’re talking about a tree with 10m polys - to apply a shell modifier to the leaves would be suicidal. Perhaps a Volume Solid shader like in Final Render might do the trick? I don’t know, just thinking out loud.
I normally use 2 sided material and growfx but I’m far from creating convincing foilage. I think it would be a combination of the said latter and some post work…
The 2sided material should work fine most of the time, but many people set it with weird values. In general leaves are highly translucent, meaning that they look darker when viewed from the lit side, and much brighter from behind. This means that the translucency value in the 2sided material must be generally set up to a brighter value. The basic set up is very easy, a green diffuse material for front/back, and a light grey translucency value, that’s all.
I was going to comment the same as Vlado here, and also add that that thread on the Ronenbekerman site is full of really strange material setups, and people generally confused as to what is what in images of foliage. The biggest issue is getting a good variation of colours on individual leaves as well as in clusters and finaly on the individual plants. So far Forestpack seems to have the easiest setup for this granularity of variation.
Very interesting indeed. We’re currently updating a lot of textures and materials at our studio, and leaves have always been a pretty tricky matter.
I have a argued that the vray2sided material is basicly flawed (atleast when used for foliage), since it simply mixes the front and the back materials. Just adding the lighting of the backfacing material to the front facing one, and completely ignoring the reflective- and prehaps even the diffuse aspects of that material would make it a lot easier to use.
Most leaves I have encountered in real life have a rich green and rather shiny top side - and a matter but brighter bottom side. This being most prominent in the silver poplar. Setting a 2sided material up to get decent translucency, yet keep the very different characteristics of the both sides is quite hard. You’ll end up with an extremely dull material if you set the transclucency higher than 128, and you will not get sufficient translucency using values lower than 128. Maybe someone has done it, but I have never been able to get it right.
Looking forward to seeing what the people at Ronen’s forum come up with.
2 sided doesnt simple mix front and back. you can set easy different/seperate speculars and reflections for both sides. (make sure to have “back side” disabled in reflection)
to my knowledge and testing it does take the material aspects into acount too (surface specularity/reflectivity) - if you make the opposite site strong reflective, only few light travels through the 2 sided, as this is in real. it is easy to test yourself (make it very strong reflecting and almost no light will travel, if only little reflection (best with ior) light will travel a lot more, as expected in reality.
so i think it is very realistic, also how it deals with shadow and transporting light from one side to the other, more or less blurred depending on distance of the object is quite nice.
stefan
p.s.: i was also amazed about the thread on beckermanns forum, many strange setups there.
I also use the 2sided material all the time. But the trade-off between specularity and transluscency is, indeed, a bit of a problem, even if it is physically grounded. Leaves are often very specular and very transluscent at the same time. I have yet to find a balance that works in all circumstances.
I always had an awful time with 2 sidedmtl and leaves… until I found out my “linear workflow” gamma settings were completely wrong. I’ve read 1000 threads and asked around but I had it way off. It took Bernhard Reider 20 minutes to spot the flaws in my gamma/workflow setup and it’s been much easier since then.
As long as we keep rendering trees that mainly look like trees because they are shaped like trees, I wouldn’t call anyones attempt at creating more organic looking leaves as somehow off the mark because the material setup is unusual. I’m yet to see 100% convincing nature renders made with Vray simply because the leaves always suck.
Agreed with the above comment, the strange nature of some of the shader setups reflect the fact that people are simply experimenting with different ways to achieve this phenomena, rather than a lack of understanding on their part. Check out their portfolio’s and you’ll see the vast majority are very accomplished visualisation artists.
Well, I beg to differ. I set up a simple scene to demonstrate the problem. The scene can be downloaded here: 2sided test Let me know if you think there’s something wrong with my setup.
The scene consists of a light, a completely black atmosphere so no ambient GI will affect the objects. A checker texture is used as a reflection override to see where the reflections are present and not. The object is a plane with polygons facing towards the camera. 2 bend modifyers are used to give the plane a slight curve.
The front material is as follows: diffuse-220RGB, reflect-255RGB, refl.gloss-1, fresnel-1.6, reflect on backside-disabled.
The back material is as follows: diffuse-128R 8G 8B, reflect-64RGB, refl.gloss-0.25, fresnel-1.6, reflect on backside-disabled.
They are loaded into three different 2sidedmaterials - one with 0%translucency, one with 50% and one with 100%. “Force single-sided sub-materials” is used in all of them.
This is the render using 2sided material:
In the front lit bottom row, the front material disappears and the reflection diminishes as the translucency increases. In the backlit top row, the reflections of the front materials also disappear when the translucency increases.
I included the reflection pass from this render where it is even more visible.
This is the result I would expect from the 2sided material, if it was to be used as paper or leaf material.
The reflective side would keep its reflection no matter how strong the backlight or how high the “translucency” (a value that in vray is a rough estimate of the materials thickness and translucent properties, really). You would also expect color to transmit through the material. In this case I have one white side and one brightly red. In a real case, a backlit “paper” would be red, no matter from which side you wiew it, as long as light travels from one side to the other. You can easily recreate this in real life by getting a glossy magazine, and viewing it in different lighting and reflective environments (for example with a window behind you, and the light in front of you, shining through the magazine cover).
I include one last render where I switched positions of the red and white materials where you can observer the lack of color bleed.
All of this is to show the basic “flaws” of the 2sided material. It is in its current state however the best option for rendering leaves, but you have to keep the translucency at a very low value to get rid of the dull look which comes when you crank it too high. This will of course make the leaf transmit less light trough, and the foliage will be darker than it should be. This can be compensated for in post, of course.
One other interesting thing with leaves is that they are full of chlorophyll, which is intenselt green and thus tints the transmitted light. I usually set the translucent color to a mild green to get that effect, especially if the backside leaf material is grayish.
The 2sided material might be working as intended, but it is not working as a piece of paper or a leaf. Atleast if you ask me.
