mia_material for realistic leaves

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  09 September 2009
i'm agree with royter and rygoody,
.-the translucency value must to be always at 1
.-the translucency color must to be an image
.-the transparency color must to be white
.-you must to play with the transparency value to get the final result.

after that, i've notice that with backlight the leaf color intensity is almost the same as it has with front light, case by case and specie by specie, is not the same a maple than an olm oak, in the second case, the translucency is near to 0.

to mimic this, i use a multiply node to multiply the translucency map intensity by 4 when i put a transparency value to 0.25.

and to get a better result you can use some 3d stuco nodes to change the leaves color in a "natural" look.


this first image without stucco, like in summer





this second one with two stucco nodes to mimic the start of the autumm, only aplied to some oaks



this with a diferent scale in the stucco nodes and some changes in the texture color



the last with the same texture aplied to all the oaks


Last edited by tostao_wayne : 09 September 2009 at 10:21 AM.
 
  09 September 2009
and finally all the oaks in red

i've play with the same leaf with 3 diferent colors


 
  09 September 2009
great shot
 
  09 September 2009
Amazing work...

....and the renders with explanations are very helpful! Thanks for sharing.
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  09 September 2009
Really great posts and descriptions. Maybe I can ad some too but I need to create some trees first of all.

Quote: 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...


I would not agree with you. My leaf shader is based on a condition node / sampler info setup where I am using different textures for the back- and foreground. Just put the texture in the appropriate slot.
 
  09 September 2009
Originally Posted by JayHoo: Really great posts and descriptions. Maybe I can ad some too but I need to create some trees first of all.



I would not agree with you. My leaf shader is based on a condition node / sampler info setup where I am using different textures for the back- and foreground. Just put the texture in the appropriate slot.



ok, the final result is exactly the same.
 
  09 September 2009
here are my progress so far:

- i deleted the condition nodes because because what i wanted was done automaticlt by the mia_material
- improved leafs orientation so they face the sky

As you see in the last exemple we barely see the texture of the leaf due to reflection and transparency power wich kills away the diffuse value. I know that this works very well for arc/solid materials, but i am not that sure if that works well for leafs.





improved reflections:


btw its unbelievable how much the shape of the tree especially leaf position is important, even if you have a perfect shader, the geometry of the tree has a very tricky role.

making a realistic tree mesh in paint effects is very flexible but a bit hard.
what are you guys using to generate those simple trees?
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Last edited by royter : 09 September 2009 at 12:50 AM.
 
  09 September 2009
Tostao, those renderings are beautiful! If possible, I would love to sneak a peek at your scene file. I've never been able to get outdoor renderings with grass and trees even remotely that good looking. Well done!
 
  09 September 2009
i know this may sound a lil stupid but...
have someone tried some "dark green" AO on the leaves? :>



try out. :x
 
  01 January 2010
sorry to bring this old thread back to life, but i m just curious if anybody got new insights or better techniques for doin this using mia_material since april.....

looking at previous posts by others, it seems like the key is to make the leaf translucent enough so that when the tree is in shadow, and back lit, sun light still come through.

the problem is if i put 0.3 transparency, or even 1.0 transparency, not enough light comes through....and i boost up the mrSky multiplier 2 or 3 times to make the leaves appear more translucent. i turned down the exposure to compensate for the increased multiplier.

all the previous post helped me a lot, and i did some tests on my own. i m not sure if it is the sampling or the filtering, but my grass look blurry and muddy, instead of visible blades of grass.

while the far away trees looks ok, the close up ones looks plastic, partly due to poor modeling....

here are my results:


 
  01 January 2010
you must to use a mulptiply node for the translucence map

if you set the transparency to .25 you must to multiply the intensity of the translucence map by 4 to get a total translucence intensity of 1.


here you can find more information about it

http://forums.cgsociety.org/showthr...2&page=12&pp=15
 
  01 January 2010
great thx a lot for that thread, seems like it has everything i need......just never thot of using a 2 sided material because the math sounds weird......

like 0.25 transparency, with 1.0 translucency, means 25% of light is getting inside the leaf...
with the backside mia_material having a low reflective value, say 0.2, means 20% of the translucent light gets reflected, so only 5% of actual light comes out of the leaf......... which is y i think u multiply the translucent map output value by 4, so u get 20% of the light out......

but it looks great from what others have posted......i ll definitely give it a try....
 
  01 January 2010
Originally Posted by tostao_wayne: you must to use a mulptiply node for the translucence map

if you set the transparency to .25 you must to multiply the intensity of the translucence map by 4 to get a total translucence intensity of 1.


here you can find more information about it

http://forums.cgsociety.org/showthr...2&page=12&pp=15


i dont understand the logic here. When you turn ON translucency (with a weight value od 1 1) then it totaly replaces the transparency. So why not just set the transprency to 1 instead of the multiply mode.




Originally Posted by yoshi95: great thx a lot for that thread, seems like it has everything i need......just never thot of using a 2 sided material because the math sounds weird......

like 0.25 transparency, with 1.0 translucency, means 25% of light is getting inside the leaf...
with the backside mia_material having a low reflective value, say 0.2, means 20% of the translucent light gets reflected, so only 5% of actual light comes out of the leaf......... which is y i think u multiply the translucent map output value by 4, so u get 20% of the light out......

but it looks great from what others have posted......i ll definitely give it a try....


could you post a comparison between a steup with multiply node and one without it?
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  01 January 2010
just to comment on 'y not turn transparency to 1 and skip multiply node', heres what i found on mental ray forum:


Quote: I assume you have conserve energy on, which means that mia_material will make adjustments.

First, it will determine reflectivity by your weight, and by viewing angle, (they are multiplied).
For view angle dependence settings, see BRDF section. What values are you using for a BRDF of the leaf?

Next, it will take the leftover weight (1 - calculated reflectivity), and look to see if you set transparency.
Then, that weight will be taken out of the leftover weight.

Finally, whatever is leftover after transparency, is used for diffuse, no matter what the diffuse weight is set to.

Now, transparency can itself be divided into translucence and non-translucence by the translucence weight factor.


so again if my leaf material is, say 0.6 reflective, 1.0 transparent, 1.0 translucent, this means only 40% of the light is coming through the material? and that the diffuse component is completely ignored.....which is mathematically correct, not sure bout physically correct, without truly using SSS......but simply not bright enough to be realistic looking...
 
  01 January 2010
Originally Posted by royterr: i dont understand the logic here. When you turn ON translucency (with a weight value od 1 1) then it totaly replaces the transparency. So why not just set the transprency to 1 instead of the multiply mode.

because the translucency only acts with backlight, so when the leaf is in a front light situation it is almost opaque. the translucency has a value near to 0 * 4 = near to 0. in the link that i have posted the tree has always a translucency map value of 4, but in the front light situation, it has almost no translucency.
 
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