mia_material for realistic leaves

#101

Yeah that’s the workflow I usually go with, just wondering why the setup Remy uses should’nt work with maya? :wink:

#102

It does, just connect the mib_twosided result to the refr_trans_weight

you could then connect another to the translucency color

You will probably need to make sure the geometry is double sided and the shader has “thin walled” on

#103

Tried that one, doesn’t seem to matter what I plug where I still don’t manage to solve the transparency-issue that Remy does by:

“For the back I wanted the translucency to be strong so the value of the transparency is on and controlled by a gray-scale map of leaves. This keeps the leaves from being transparent.”

#104

Just use more twoSided shaders.

MIA shaders need to have transparency on for translucency to work. If things start to look TO transparent, lower the refraction gloss.

So connect the outA of a twoSide shader to the transparency. Connect another to the color, and a third to the Weight.

That will completely isolate the two sides so you can treat them as seperate surfaces.

Dont forget that Black translucency color is essentially turning it off.

#105

I think you can exceed poly limit restricted by 1 million in “paint effects to poly” option dialog. In the strokeShape node in Mesh Output rollout you can change poly limit.

#106

Quote:
Originally Posted by royterr
ideally one would choose a big surface and paint it with a huge pfx brush (one stroke) and ajdjust the blade scale, but thats not possible (unlike onyx grass generation) because the pfx mesh options has triangle limit option.

I think you can exceed poly limit restricted by 1 million in “paint effects to poly” option dialog. In the strokeShape node in Mesh Output rollout you can change poly limit.

Set the poly limit to 0 for no limit.

#107

Guys, I know this information is somewhere on the forum but i tried googling and stuff but can’t really find the answer any more though I know I skimmed by it once.

I am testing out this stuff on Vray 1.5 so if you have information specific to that it would be great but I guess it would work either way.

How do I go about assigning different textures or shaders to create variety. Isit with the ray switcher? Is there an easy way to do this?

I am using proxies which are then instanced across. I aint good at mel so I am hoping there is a simple solution. but if there isnt. do just tell me where to look. ill figure it out. thanks guys

#108

Try this section of the forests in mental ray thread. It’s dealing not with MR actually, but with UV-maps for multiple leaves in one shader.

Tastao_wayne has some excellent inside into this topic. He runs a script, which he wrote, which separates all your leaves into a 3x3 UV set. This lets you use 9 different leaf textures per tree, basically. I’ve not used this script yet but his results are astounding - best I’ve ever seen, by a pretty large margin even.

This post specificallydelineates his technique.

#109

http://www.djx.com.au/blog/2009/03/04/mifinalgatherhide/#more-130
this should be helpful to understend how light pass through the sufrace of leaves so deep, i think.
sry for my bad english

#110

Am I correct in assuming that the color variations (some patches are yellowish while others are a bluer green) is being driven by the Fractal? If so could someone please explain how exactly the Layered texture with a fractal mask is being set up and used in the MIA? Or is this really 5-6 different MIAs with the color shifted in each one?

Thanks in advance

#111

You can use the fractal conected to a blend colors node.

#112

I can see how that would affect the color on each individual grass blade but based on what I’m seeing in posts # 95 and 97 it appears to be modifying the color of grass patch as a whole. If this is true, I wonder what shader network connects are necessary to modulate the color of a huge grass patch from brown to green using a fractal as a mask(or just a blend color node)?

#113

I’ll give you one example how I did it las time.
Create a low saturated diffuse texture for the grass and put it -well in the diffuse channel.
Connect a ramp/noise/whatever as projection (right mouse button in hypershade by creating the node) in Y direction into the colorgain channel.
Resize it to group bounding box.
Now you’re obviously able to change the hue of the grass based on your planar mapping.
Voila.

One could also make a y-planar UV snapshot and paint the whole color texture in photoshop for mapping purposes.

Basically that’s how I managed to colour a huge field of binaryproxy patches - all attached to the same MIA shader - like a football field.

#114

http://img21.imageshack.us/img21/584/04forest.jpg
In this image we can see how light passes through the leaves gently and gradually fades.
With the use of translucency we do not get this effect… as with the use of refraction. How can we to achieve this effect? without direct light, only for mr sky. I spend many time working on this and I still far… I try to reconnect shadow node for mia material, on mib_shadow_transparency. Then I reduce the color of transparency… this works but not properly. So i stuck… any ideas?

Sorry for my bad english

#115

Uploaded with ImageShack.us

this is what i’ve got… but only with mia_protal

#116

@slam-k: That render looks cool, but it not a realistic light transmission example at all. The second and third planes down appear to be as bright as the top one; there are some materials which may react this way, but vegetable (leaf) matter does not. If you take a length of string and say, ten actual leaves in real life, and dangle them roughly the same space apart along the string, and then hold them up in the sunlight, you see nothing like what you’ve rendered here. Granted, as you space the leaves closer together, you’ll get more occlusion of course, and light transmission is certainly species-dependent…

But most of this can be handled automatically using Final Gather itself. Here are some examples:

10 leaves, area spotlight (disc), 1 secondary FG bounce:

10 leaves, sun/sky, 0 secondary FG bounces:

20 leaves, sun/sky only, no secondary bounces:

20 leaves, spotlight w/photon GI & caustics for comparison:

slam-k http://img21.imageshack.us/img21/584/04forest.jpg
In this image we can see how light passes through the leaves gently and gradually fades.
With the use of translucency we do not get this effect… as with the use of refraction. How can we to achieve this effect? without direct light, only for mr sky. I spend many time working on this and I still far… I try to reconnect shadow node for mia material, on mib_shadow_transparency. Then I reduce the color of transparency… this works but not properly. So i stuck… any ideas?

Translucency only plays a role if you’re viewing the underside of the leaves. It has nothing to do with the transmittal of light, in the mia_mat_x. The refraction transparency strength however does affect the transmittal of light, and also the settings “thin walled/solid” and “refractive caustic/transparent shadow” affect the look tremendously. You don’t need an mib_shadow_transparency node at all if you’re already working with the mia_mat_x.

What you’re seeing in the render you posted there of the trees is the Final Gather filtering in effect really. The darks are more precise with a filter of 1, and the lights too. If you’re rendering with a filter of 0 (default), you’ll never really get this contrast, which is mostly geometry-based and not based on the shaders so much. You cando the same thing with Blinns or Phongs and get similar results, so long as your geometry and foliage is dense enough.

My point being, in your lit planes render example, leaves do NOT act like this at all. The second and third leaves in will be reasonably darker than the first, not bright white. And subsequent leaves will still be lit partially due to the indirect lighting of the Final Gather calculation; this is where you can adjust the depth using FG scale if you like, the filter settings, and of course how many secondary bounces you want to see.

#117

thanks for the detailed response. Very usefull info for me.

Another thing I cant understand is - how leaves can at the same time pass light in some place, and block in other?

http://img7.imageshack.us/img7/3928/12selva.jpg

Look at this image, where leaves pass light with such force, that they become pale green.
How can it be? I cant understand this. and there is another problem driving me crazy… why shadows under house completely black? This is AO post processing?

#118

DOn’t take the image as render image, More post in the images, so post effects is your help.

and no post effects like render passes or layer AO. Only exr 32 bit AE in post.

#119

prodan never said that he didnt use an area light above those trees to accentuate the indirect sky light.

#120

Ye i thought about that… i used portal light with mrsky but this never worked out for me.

I need to get reflection with glossy highlights on the grass. How can i achive seenable glossy reflections on it? Its either reflects far too much or just doesnt at all ,despite parameters of BRDF i used. I use only mrsky without sun and photographic exposure control. When i use portal light theres no changes on image.