New double sided thin material - tests

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OnoSendai
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New double sided thin material - tests

Post by OnoSendai » Tue Sep 25, 2012 12:47 pm

As anyone who has tried to create a truly realistic leaf material in Indigo knows, it's not currently possible, at least if you model the leaf as a flat polygon.

Real leaves look quite different on the front from the back. The top of the leaf is often smoother, reflecting light in a more coherent way (higher exponent in Indigo language). the top of the leaf is also often darker than the underside.

Currently in Indigo, all materials look the same on the front as they do on the back. So to render realistic leaves, I will introduce a two-sided material model.

It's also important to be able to render the light that's scattered and transmitted through the leaf. For that, the diffuse transmitter material does a good job. However, blending phong with diffuse transmitter isn't really correct, as the specular reflection should take place before light is either back-scattered or forwards scattered in the substrate / leaf interior. Anyways, by building in the diffuse transmission to the model, the new material is more correct.

When the leaf is lit from the front, you can see that the leaf colour differs based on if the leaf is front or back side towards the camera: (The leaf on the right has the front/top side towards the camera) The light is behind the camera.
frontlit.jpg
When lit from the back, the leaf looks the same from both the front and the back. This is also what happens with a real leaf (try it!)
backlit.jpg
The roughness (exponent) of the top can be varied independently of the roughness of the bottom of the leaf.
In this render the leaf on the right is frontside-up, on the left backside-up:
toplit.jpg

This new material should allow people to create extremely realistic leaf renderings.
It will be available for beta testing after the 3.4 stable release.

Any questions or feedback welcome!
Attachments
leaves2.jpg
leaves1.jpg

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Pibuz
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Re: New double sided thin material - tests

Post by Pibuz » Tue Sep 25, 2012 7:21 pm

Only one question: WHEN WILL THIS BE IMPLEMENTED IN SKINDIGO?!?!
:lol: :lol: :lol:

Jokes apart, thanks: seems like glare is really busy on the shaders' topic, which in my opinion was the only thing a little under-rated. Good work, thanks!

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Re: New double sided thin material - tests

Post by wlf_alex » Tue Sep 25, 2012 9:26 pm

It is a good news!

thanks a lot..
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FoXar
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Re: New double sided thin material - tests

Post by FoXar » Tue Sep 25, 2012 10:02 pm

I can't wait! this will be great to (finally) have implemented :D
Cheers,
Roo Evans

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solarray
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Re: New double sided thin material - tests

Post by solarray » Tue Sep 25, 2012 11:07 pm

I have one question regarding the usage of this material, because I think it could be quite useful for other objects as well. As you discribed the differences of a leaf behaviour in real world, it came to my mind that this situation also fits very well for bird feathers, right? Feathers have also a different look on the back than the front. The back side is also more rough than the front. But I think you will also need two different diffuse images for the back and front. This is the thing I didn't got from your post. Is it possible with this material to use different images on front and back side for diffuse or bump channel ?

Overall, great news and thanks for implementing!
cheers

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New double sided thin material - tests

Post by zeitmeister » Tue Sep 25, 2012 11:28 pm

Fantastic, Ono!
Her damit, aber flott! :-)
Cheers, David



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CTZn
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Re: New double sided thin material - tests

Post by CTZn » Wed Sep 26, 2012 12:33 am

I would kind of second solarray and ask for the material xml description, for reference please.

Notes for instance have the same optical properties on both sides generally speaking, but two faces. Is this also covered ?
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Re: New double sided thin material - tests

Post by OnoSendai » Wed Sep 26, 2012 12:53 am

solarray wrote:I have one question regarding the usage of this material, because I think it could be quite useful for other objects as well. As you discribed the differences of a leaf behaviour in real world, it came to my mind that this situation also fits very well for bird feathers, right? Feathers have also a different look on the back than the front. The back side is also more rough than the front. But I think you will also need two different diffuse images for the back and front. This is the thing I didn't got from your post. Is it possible with this material to use different images on front and back side for diffuse or bump channel ?

Overall, great news and thanks for implementing!
cheers
Hi Solarray,
You can use a different texture map for each side. Actually you can even use a different material for each side, so you could use e.g. Oren-Nayar on one side and diffuse on the other.
The bump has to be the same on both sides.

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Re: New double sided thin material - tests

Post by OnoSendai » Wed Sep 26, 2012 12:54 am

CTZn wrote:I would kind of second solarray and ask for the material xml description, for reference please.

Notes for instance have the same optical properties on both sides generally speaking, but two faces. Is this also covered ?
I'll post some xml later tonight.

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Re: New double sided thin material - tests

Post by OnoSendai » Wed Sep 26, 2012 1:16 am

Pibuz wrote: Jokes apart, thanks: seems like glare is really busy on the shaders' topic, which in my opinion was the only thing a little under-rated. Good work, thanks!
Indeed, it's been a while since we have worked on materials.
As well as this double sided thin material, we'll also be adding a coating material, as well as adding back Fresnel scale to Phong, and improving Phong a little bit in general.

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solarray
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Re: New double sided thin material - tests

Post by solarray » Wed Sep 26, 2012 1:29 am

Great, looking forward to it

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Pibuz
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Re: New double sided thin material - tests

Post by Pibuz » Wed Sep 26, 2012 1:33 am

OnoSendai wrote:
Pibuz wrote: Jokes apart, thanks: seems like glare is really busy on the shaders' topic, which in my opinion was the only thing a little under-rated. Good work, thanks!
Indeed, it's been a while since we have worked on materials.
As well as this double sided thin material, we'll also be adding a coating material, as well as adding back Fresnel scale to Phong, and improving Phong a little bit in general.
..not to mention the uber-introduction of velvet materials!

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CTZn
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Re: New double sided thin material - tests

Post by CTZn » Wed Sep 26, 2012 1:53 am

OnoSendai wrote:
CTZn wrote:I would kind of second solarray and ask for the material xml description, for reference please.

Notes for instance have the same optical properties on both sides generally speaking, but two faces. Is this also covered ?
I'll post some xml later tonight.
In fact a list of parameters would do, it is just to have an idea of the material parameters/ressources. edit: I have read your last posts and that's fine by me. A very nice addition !
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delle
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Re: New double sided thin material - tests

Post by delle » Wed Sep 26, 2012 7:07 am

Hi, great news!

One question: One of the two materials can be "an invisible material"?

If so, you have just created a triangle visible only from one side!

If so, you have just solved this problem: to create a wall that is "opaque" internally (it reflects back the light)
but invisible from the outside.

A see through wall!

Delle

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Re: New double sided thin material - tests

Post by Polinalkrimizei » Wed Sep 26, 2012 7:24 am

Whoop-whoop!

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