mia_material for realistic leaves

#41

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/showthread.php?f=87&t=804892&page=12&pp=15

#42

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…

#43

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.

could you post a comparison between a steup with multiply node and one without it?

#44

just to comment on ‘y not turn transparency to 1 and skip multiply node’, heres what i found on mental ray forum:

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…

#45

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.

#46

i’m not totally sure, but the transparency of the object is determined only by the transparency value and the angle between the camera and the surface and the BRDF, the reflectivity is more or less an aditive proces, so don’t take it in acount.

#47

i have difficulty understanding this.
whats the main difference between transparancy1/ no sss mltiplier and transparancy 0.25/sss 4 multiplier?

#48

With transparency 1 -> leaves totally transparent -> almost flat foliage
with transparency .25 -> leaves not totally transparent -> volume foliage

but… you want a translucency intensity of 1 (near to the color that the leaf has with front light), so the only way to get this is to use a multyplier to increase the value of the translucence when the transparency is set to .25

the problem is that translucency and transparency must to be independent channels, but in mia_material, the intensity of the translucence is controled by the amount of transparency.

an example: the human skin is totally opaque but has translucence.

#49

here r my low quality test renders with the translucency multiplier…with 1 mia_materil, not 2 sided shader

with multiplier:

without:

it s an improvement…maybe denser grass and better trees…

#50

Another thing that’s really important is to have more than 1 leaf type per tree! (ie three leaf shaders per tree)

Not 100% necessary…but if you don’t (unfortunately I didn’t with this rendering test I did) you can tell each tree individually and it is not as realistic!

I’m still interested in Alessandro’s leaf shader workflow! :wink:

#51

i like how it looks with multiplier, are you ussing mia_exposure_protographic?? if not, try it

#52

impresive Hamburger, i like it :beer:

totally agree with you, its really important to have more than 1 leaf type per tree, one solution for it is to use some stuco nodes and plug diferent shaders in each channel.

i’m interested too in Alessandro’s leaf shader workflow

#53

Don’t know if you’re using Onyx for your trees, but if so you can specify how many different leaf objects you need in the export dialogue. This makes texturing much easier, and I usually try to use at least two different leaves as well, if not more for foreground trees.

#54

I have a noob question
where do you plug the multiply node into the mia material translucency options. is it the color or the weight?

#55

the color, the weight always to 1.

#56

in the other thread u posted ur leaf textures, i m wondering how did u get the leaf to look very diffuse lit.

all the leaf texture i found from google has specular highlights, which i dont really want.

on a 2nd look are your leaf texture hand painted?

#57

they are scanned, with a white background (some A4 papers (4 or 5)), but without to close the scanner.
The intention was to get a more or less plain leaf but not totally plain.

#58

just hand paint them man, it will look a lot better and you can actually put detail where you want to.
and if you’re not good at painting then there’re a few photoshop filters that flatten the color, I think it’s called High pass or something like that.

#59

i will probably end up hand painting them, since i dont have a scanner, and it s hard to find several different leaves that are front facing and diffuse lit online.

so back to the texturing part…the mib_twosided shader, here r my thots…i dunno which way is better in terms of realism/speed

config1 (it seems i can only do this in maya, i cant plugin a mia_material in the top/btm slot in max, cuz it s a map):
mib_twosided shader:
top --> mia_material for top leaf side ( includes top diffuse, bump, translucency, reflectance map)
bottom --> mia_material for bottom leaf side ( includes btm diffuse, bump, translucency, reflectance map)

config2:
mia_material:
diffuse: mib_twosided with top/btm img
reflection: mib_twosided with top/btm img
etc…

sounds like i m stuck with option 2 in max

#60

if you use the second method you will must to use a map for every value that change form one side to the other, from my point of view too much maps, and a very confuse shader network