[REQ] Indigo instance color variation shader

[zeitmeister]

Hey,

I just came up with that idea having a look at Vray.
What it means: the ability to vary the color of a material with each Indigo instance.

For example:
One phong material with a texture or color in the diffuse color channel. On top of it, or as an option below it, the ability to vary the color or brightness of this texture or color. Let's say for example a gamma range from -0.2 to +0.3 of the original value.
Distributed over all Indigo instance objects which use that material.

This will tremendeously help to create realistic color or whatever variation when using many instances, like trees, a wood, grass, or whatever you can imagine.

What do you think about it?
I could be an ISL feature, but organically integrated into the existing exporters.


Just some thoughts.

[suvakas]

You don't need to change Indigo for that.
It's pure exporter thing.

[zeitmeister]

So is it possible to call Indigo render instances per ISL?

[Zom-B]

suvakas has such a feature in Maxigo, its all about control in the exporter for this feature!

http://www.indigorenderer.com/forum/vie ... 711#p73711

[suvakas]

So is it possible to call Indigo render instances per ISL?

I'm not exactly sure what do you mean by ISL ? It's exporter that defines color/gamma of material. You can use it with ISL too of course.
The example image Zom-B posted has slightly different color for each instace and color is generated during the exporting process. It can be a random color, it can go from light to dark, it can be based on a bitmap (which is the case with my tree images) etc. But it's exporter that does all the work.

[zeitmeister]

Yikes... awesome!
Then please tell Yves how you did that!
This should be a feature implemented in every available exporter!

[suvakas]

I'm sure Yves knows how to do that
He just needs to change color or gamma values randomly for the instances. Maybe add some parameters to control the range.

[galinette]

Agree with zeitmaster : that would be a nice feature to access instance's id in ISL. I'm thinking of interesting ideas not easily done with the exporter

Etienne

[OnoSendai]

You could vary some parameters (e.g. colour) with world space position.
Having access to the instance id is also an interesting idea, maybe I'll add that or something like it soon.

[fused]

Yikes... awesome!
Then please tell Yves how you did that!
This should be a feature implemented in every available exporter!

I once did color variation in instances for cindigo, but scrapped it

can be done, easily

[galinette]

To illustrate my previous post, here is what I'm thinking of:

Building glass façades are not flat, but they have a slightly wavy surface, which is very visible when for instance you see the reflection of another nearby building.

To model that, the simple way is to use bump or displacement shader with waves (similar to water materials). However, I'm not fully happy with this, it does not look as the real façades.

The reason for this is : it's not a wavy profile. It's a combination of window tilt, twist and "pillow" deformation. The tilt and twist are due to mounting disaligment, the pillow to some thermal constraints.

That could be achieved by using a bump or displacement map that is a linear combination of these four functions:

deform.jpg (18.66 KiB) Viewed 422747 times

The coefficients are carefully randomly chosen, and unique for each window. This would be very elegant and convenient to generate them from a seed computed as a hash of the instance id. Then, nice window materials could be released. The user of these materials would only have to ensure the windows has UV coordinates mapped to (0,0)-(1,1) and instanciate them on the whole building.

I'm sure there are ways to do this on the exporter, but far less easy and elegant.

Regards,

Galinette.

[zeitmeister]

Yeah, there are many things possible with this function. Also, such an instance random factor could maybe affect the position, rotation and scale of the instances, too... controlled by noise or a texture map.
But that's future music, I would be glad having the colr random option for now!

[zeitmeister]

BUMP.
Can someone please provide a sample code for color variation on instances?
That would be so nice!
Best way: to alter gamma values of a texture randomly.

I found that exampe here:

Code: Select all

def eval(vec3 pos) vec3 :
  let
    r = real(objectId())
    base_col = vec3(0.6, 0.4, 0.4)
    random_scale = 0.1
  in
    base_col + vec3(
      fract(r * 45.345),
      fract(r * 4.57),
      fract(r * 908.3)
    ) * random_scale

But how can I translate it to alter a given texture?

Thank you!!!!

[Zom-B]

Haven't I told you how to archive that easily in C4D already Zeiti?

[zeitmeister]

You did, but this way doesnt work in lots of my scenes... I am scattering a load of objects, with several sub-objects in it.
Using your solution is a lot of work, because I have to materialize each single instance.
Having a shader doing that, with lot more random colors and colored textures would be the way to do it.
And to be honest: it doesnt seem to be a big problem for someone who can code.
Same with scattering objects:
There are quite nice functions provided by Indigo which arent being supported by the exporters.
I think that Glare also should focus on them.