mia_material for realistic leaves

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  09 September 2009
One thing to note. Reflection, refracton and shadow raytracing depth have absolutely no effect whatsoever on the nature of how mia_material translucency propagates lighting through the leaves. You can leave all of them at 1 with no change in lighting.

Now, to be physically correct you want translucency weight at 1, since no leaf or grassblade is semi-transparent, they are fully translucent. So for all purposes of leaves and grassblades I set tranclucency weight to 1 and control the level of translucency purely with the transparency slider.

Transparency 1.0 (the darkness comes from me having the FG filter set to 2)


Transparency .8


Transparency .6


Transparency .4


Transparency .2


Transparency 0



Now one thing about that series of images above is, the translucency color is brighter than the leaf color. I think that in some ways that makes it look more realistic because looking behind the leaves in the sun they appear brighter, but is that physically correct?

Here is a series of images where the only thing I'm adjusting is the brightness of the translucency color, which is a slightly yellow solid color. Transparency is set to .4 in all images.

Translucency Color 1


TransclucenyColor .6


TranslucencyColor .3


TranslucencyColor .1


So I think thin-walled translucency by itself is very capable of propagating a SSS effect through leaves by itself. The misss shaders I do not think are necessary. Just properly adjusted mia_material.

I think physically accurate would be with the diffuse color and translucency color about the same level of brightness. Then make the translucency color slightly tinted yellow, and maybe increased .1 brightness just for a little more behind the leaf shine.

Last edited by rygoody : 09 September 2009 at 04:40 AM.
 
  09 September 2009
Quote: I think physically accurate would be with the diffuse color and translucency color about the same level of brightness. Then make the translucency color slightly tinted yellow, and maybe increased .1 brightness just for a little more behind the leaf shine.


and heres some renders with those settings









and some allesandro style-esque color correcting



only not as good

here is the scene file if anyone wants to run some more tests
http://www.4shared.com/file/1300837...8/treeTest.html

Last edited by rygoody : 09 September 2009 at 05:15 AM.
 
  09 September 2009
Originally Posted by royterr: for mid range/ background leaves, i would definitivly use the mia_material with similar values.

tharrell, thanks alot for the info, your method is specially useful for hero objects.
- if i got it right you copy and paste the lightmaps of a misss_fast_skin_maya shader to the mia_material SG.
- drag the sss shader to the additional color of the mia_material
- apply the mia_material to the object.
-turn off diifuse color and weight of the sss shader (what about the overall color slot?)
- play around with the "Subsurface Scaterring layer" values

- But mastezap mentioned that you also should turn off "unscattered diffuse" in the sss sahder. I can't find that section

-did the AD fixed the bug of lightmaps rendering superslow with FG in Maya 2010?


Whats the "additional color of the mia_material"? In SG; Custom shaders>material shader? or ? Confused on that part.

And could the light maps also be connected to the light map shader attribute instead of being copied and then connected?
 
  09 September 2009
Originally Posted by Mrguy: Whats the "additional color of the mia_material"? In SG; Custom shaders>material shader? or ? Confused on that part.

And could the light maps also be connected to the light map shader attribute instead of being copied and then connected?


the aditional color is simply a slot in the advanced section of the mia_material.

i dont know how lightmaps work and if 2 materials can share the same light map.
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  09 September 2009
I must be blind... is it a feature in 2010 only? I'm in 2009.

I'm checking out the shader network rygoody put up and he has oakLeaf.tif hooked into the cutout opacity? Not same thing?
 
  09 September 2009
Quote: I'm checking out the shader network rygoody put up and he has oakLeaf.tif hooked into the cutout opacity? Not same thing?


Cutout opacity is where you put your alpha channel for cutout, as opposed to directly into the Transparency section on a standard Maya Blinn or Phong shader. Most of the time you'll need to check "Alpha is Luminance" on your file node too.

"Additional Color" is directly below Cutout Opacity in Maya 2009's mia_material_x. I haven't been using Additional Color on mine yet though... That said, I'm not getting results as sweet as Roy's in my leaves just yet. Close, but not as close as I'd like... Playing with translucency and transparency seems to be getting me close, but my scene's got seven different trees so far and tweaking them one by one is becoming tedious. Might have to create a break-out scene and then copy the material settings back in, for the sake of speeding up test-renders.

I'm not using SSS in mine (yet!) and hope not to, but if that's what it takes... The scene's already becoming almost too bulky, even under x64, so even more calc and render time might not work for me in the long run. Or, of course, a scene tear-down and reconstruction might help. I have a tendency to get sloppy with nodes on large projects.
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  09 September 2009
Thats odd... I just got home and that section wasn't sowing up on my work computer for soe reason but shows up at home.

Ok very cool I'll work more on it tonight. I was actually going to use the setup for a face that I modeled.. sill far off but wanted to experiment a bit. I'm familiar with SSS Mix20 and blinn network but not mia and SSS so it intrigued me.
 
  09 September 2009
Originally Posted by InfernalDarkness: Cutout opacity is where you put your alpha channel for cutout, as opposed to directly into the Transparency section on a standard Maya Blinn or Phong shader. Most of the time you'll need to check "Alpha is Luminance" on your file node too.

"Additional Color" is directly below Cutout Opacity in Maya 2009's mia_material_x. I haven't been using Additional Color on mine yet though... That said, I'm not getting results as sweet as Roy's in my leaves just yet. Close, but not as close as I'd like... Playing with translucency and transparency seems to be getting me close, but my scene's got seven different trees so far and tweaking them one by one is becoming tedious. Might have to create a break-out scene and then copy the material settings back in, for the sake of speeding up test-renders.

I'm not using SSS in mine (yet!) and hope not to, but if that's what it takes... The scene's already becoming almost too bulky, even under x64, so even more calc and render time might not work for me in the long run. Or, of course, a scene tear-down and reconstruction might help. I have a tendency to get sloppy with nodes on large projects.


No need for an SSS shader because we are dealing with an open surface not a solid object.

I find the PF perset a good starting point, but you have to play around with twigs/branches/leafs settings alot to mimic real world trees.

Transulcency value should always be set to 1

For Translucency color:
-i think that using a flat color gives unrealistic results (check the back of the leaves, you will see an unatural flat color)
-Using a lighter version of your diffuse texture gives a very weak translucency result
-The Third opyion is to use a texture of the other side of the leaf wich is a solution bteween the last 2.
Frankly I don't know wich of these 3 options Masterzap wanted us to use.

For trasparency value:
-Everyone is using a value between 0 and 0.4. But when using a 0.8 value the leaves at the edges of the tree give a strong SSS feel but the areas in the shade look a bit "flat" due to this high translucency value (driven by the 0.8 transparency value).

That's what i found for now. I guess the big mystery lies in the last 2 points.
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  09 September 2009
Originally Posted by royterr: For trasparency value:
-Everyone is using a value between 0 and 0.4. But when using a 0.8 value the leaves at the edges of the tree give a strong SSS feel but the areas in the shade look a bit "flat" due to this high translucency value (driven by the 0.8 transparency value).


If that's the case, you could use ambient occlusion as the value for transparency. The interior leaves would be dark in the AO pass so they would be between 0-0.4. The outer leaves would be occluded very little so they would be close to 1 in value. You chould then remap or clamp values so that no leaf's transparency goes above 0.8 or below 0.2.

..this may be overkill though.
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  09 September 2009
Ok as promised here are my results:


The most intresting result is the last one because it combines reflection on top of the leaves just like Alessandro's renders.
It's not perfect but close.
One of the key tricks is to have leaves facing the sky (more precsely the sun) in Paint Effects wich is quiet hard to achieve. i will post more details later:
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  09 September 2009
Awesome.

How did you achieve the topside and bottomside transparency numbers being different values? I'm no shader genius to be honest, and don't use a gamma-correct node workflow, so I'm having a hell of a time following your shader network.

The results are great to see though... I haven't learned or made this much progress in Maya in years, and you've been a great help. I find myself actually playing with Maya at home again, instead of loathing it after a long hard day's work and never opening it at home.
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  09 September 2009
how's my try ?



1080p version here
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  09 September 2009
Hey InfernalDarkness I believe it's the condition node.

http://greensoda.squarespace.com/bl...er-in-maya.html

And gamma nodes are just for on the spot adjusting right? Fix it in Maya rather then bring it back into PS?
 
  09 September 2009
Mrguy, you are right, i am using the gamma correct node because i am using a 2.2 gamma value in my mia_exposure_simple.So you have to correct everything, even color swatches ( i am not sure wether you have to gamma correct the "Ambient Shadow color" in the AO section)

As for the condition node, its very simple: you have a sampler info node that's inputing information about the normals and it's plugged to the first term of the condition node. and the condition node sees if the condition is availables ( so normal fliped) so if "color if true" has a white value (0 0 0) and "color if false" a 0.35 gray value.

I will post some more renders with better trees soon.
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  09 September 2009
Originally Posted by royterr: Mrguy, you are right, i am using the gamma correct node because i am using a 2.2 gamma value in my mia_exposure_simple.So you have to correct everything, even color swatches ( i am not sure wether you have to gamma correct the "Ambient Shadow color" in the AO section)

As for the condition node, its very simple: you have a sampler info node that's inputing information about the normals and it's plugged to the first term of the condition node. and the condition node sees if the condition is availables ( so normal fliped) so if "color if true" has a white value (0 0 0) and "color if false" a 0.35 gray value.

I will post some more renders with better trees soon.


royterr, in my opinion is a better way to use a Mib_twosided sample compositing instead a sampler_info.

by this way you can handle two independients mia_material, one for each side, you must think that for example the bump for one side must to be the oposite for the other side...

Last edited by tostao_wayne : 09 September 2009 at 08:44 AM.
 
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