Grass

[Zom-B]

I always thought to this Indigo shader to be quite similar to 3dsMax's hair and fur modifier, which, I assume, creates the geometry from scratch...

Implicite Surface would be the tool do do so, but this is in experimental stadium as far as I know

[doreamon]

Grass in indigo? which one renders faster in indigo?

Displacement
Does indigo have micropoly displacement?

or real geometry instanced and scattered.
Instances that can be done in the host app and translated into indigo as instances?

[zeitmeister]

Go for geometries instances.
Indigo will understand them from your host app.


Cheers, zeiti

[CTZn]

micro-polygon displacement is available, also in vector form eventually. Even procedural surfaces will get you grass blades, but instancing is the most performing.

[Jay-ko]

The grass materials in the database are not enought to mimic a real grass with accuracy.

Find here a test to challenge material on a 3D grass mesh, scattered by Forest into 3ds Max.
-the phong material have the same response than the diffuse transmitter.
-the diffuse albedo material is ugly.

I do not really understand why the DT react like a simple phong here.
These materials does not looks good to mimic grass.

Are you agree with me?

[Oscar J]

What kind of lighting are you using here?

[Zom-B]

Find here a test to challenge material on a 3D grass mesh, scattered by Forest into 3ds Max.
-the phong material have the same response than the diffuse transmitter.
-the diffuse albedo material is ugly.

Look slike you mixed stuff up... quite much!

The ugly material looks like being Diffuse Transmitter only!
The two other renderings looking the same, well... there is a big chance they are!

Why don't ya use DoubleSided Thin material?

I could not find any of these Materials in the online Database: http://www.indigorenderer.com/materials/categories/7

If you want proper Feedback, please upload that materioals as PIGM.

[Jay-ko]

Yes I had badly renamed this image file.

Find here something more consistent.
Each images have been render with the same parameters with a linear tone mapping.
The light come from a real HDRI. This HDRI represent a sunny sky.

[Zom-B]

Hey Jay-ko,

here a few comments:

- The Phong + DT Material is mixed 50/50. Usually 20% of DT should be enough.
Also depending on your grass mesh, if you have single sided grass leaves the DT gamma should be at 2.2.
If you have a grass mesh with an volume, then set the gamma to 1.0.

- The DoubleSided Material is "unfinished"! you only have applied front + back color. There is no Transmittance texture or one for the thickness of the leaves. also roughness is at default values, creating some very shiny material. Check this here for more informations: http://www.indigorenderer.com/documenta ... sided-thin

- Your Grass seems to float in the air. For proper result you should have some ground floor

- check a close up render of your Grass to see how the scatter does place the grass, maybe its quite a dense mess where all the grass cuts into each other.

Phong and Double Sided Material could use roughness maps, fresnel maps and exponent maps for more detailed render output (maybe not that much for rendering so far away)

[Jay-ko]

This is very interresting; thank you for these comments. It is more clear for me now.

Find here a couple a images to understand how the model that I use in my scattering is.
See the picture with the "under-ground" point of view, I added it to basically undestand the grass scatering.

Then find the IGM file of the 2sided material with upgrade as suggested.
And finally the result in the same conditions.

I understand that it is more logical to use a 2sided material. Are you agree?

[Oscar J]

More logical yes, but also much slower.

I actually don't think you grass looks all that bad considering the scene and lighting setup.

[Zom-B]

You need to save the material as a PIGM so textures are zipped into that file, not only a igm.

Regarding the look of the finall scattered grass its not only about the material, but quite a lot about the scattering. If the scattering is to uniform it gets boring and less lifelike, here an very extreme example: http://farm4.static.flickr.com/3631/347 ... 09e611.jpg

More logical yes, but also much slower.

Double Sided thin has get a massive speed boost in Indigo 4 btw

[Jay-ko]

Hello Guys,

Just a tiny stuff in python to change the materials uid in a range to create "almost-random-variation" for that kind of scattering.

Says me if that help!