Isotropix Forums

Scattering small vegetation: grass fields, corn fields...

General Discussion about Isotropix and CG related topics

Re: Scattering small vegetation: grass fields, corn fields..

Unread postby shadow92 » Fri Dec 13, 2019 11:45 pm

Hi guys,
I would also like to add my question into this topic - how do I actually blend between multiple scatterers? I read above that I should use procedural noise but Im not sure where to plug it. I can not plug it to point clouds decimation texture, because Im using gradient there to limit the slope.

What Im trying to achieve is a natural vegetation system with grass, plants, etc.
Basically I have a ground terrain (alembic) from Maya and now I have 3 types of scatterers
- small grass and plants
- taller grass and big plants
- forest
All of these have their own point cloud decimated by slope angle (gradient texture). Now Im trying to combine these scatterers into one output where I would use either a procedural map or imported RGB texture to define say R will be small grass, G for tall grass and B for forest... Im still kinda new into these things and its a bit confusing to me.

Can anyone shed a light into this more in depth?

Thanks!
shadow92
 
Posts: 18
Joined: Wed Jun 13, 2018 12:46 am

Re: Scattering small vegetation: grass fields, corn fields..

Unread postby esmith » Sat Dec 14, 2019 12:35 am

Hello, so for me when doing these types of things I usually don't try to get everything from the tiniest grass to the largest tree, in one single scatter system. I guess this depends on your shot, but usually, if my tiny grass intersects with my medium shrubs, it's an invisible error.

But to your question here is one method.

The basic setup is to populate the scatterer by a Luminosity value, instead of Random. You do this by the Scatter Input Mode variable on the scatterer.

The items in the list are scattered AS a list. So in my template here...White is the tall trees on the top of the hill, and Black is the tallest weedy grass. This is driven by a gradient, so that I can tune this, to get the assets I want on the correct portion of the hill I'm also using some fractal noises to "dirty up" the edge between each "band" of plants in my scatter list.
Capture4.JPG

Capture5.JPG

Capture6.JPG
Capture6.JPG (17.32 KiB) Viewed 944 times


Another way to use the Luminosity Scatter Input Mode is to just simply project down some noise to drive what things are scattered where. Again this will be just a black and white texture noise. But it has quite the effect, and depending on your art direction, a more realistic positioning of plants especially.
Capture7.JPG

Capture8.JPG


And yet ANOTHER way to leverage this is in this case, I'm using a map of the height of buildings in Melbourne, Aus, to drive a single scatterer. Of course I am also removing instances by using Scopes. to place in bespoke geometry "for my shot" which is something important to say. Always remember you can scope out an area and place a different scatterer in that exact location, that's how I'm building my park. Of course I could have put the trees at the bottom of my list, and just made sure that the blackest blacks in my image are where I wanted to put the Trees.
Capture9.JPG


I'm also attaching a zip file with 4 projects showing some other methods for influencing the distribution of points and objects.

Hope this helps, there are many many ways to get the same exact result, so for me I'm usually just trying to do the quickest way to get a result.
Attachments
Scatterers.zip
(18.64 KiB) Downloaded 67 times
User avatar
esmith
 
Posts: 168
Joined: Mon May 22, 2017 4:11 pm

Re: Scattering small vegetation: grass fields, corn fields..

Unread postby shadow92 » Sat Dec 14, 2019 3:58 am

Thank you so much Eric for your answer!

I usually don't try to get everything from the tiniest grass to the largest tree, in one single scatter system

Me neither, thats exactly my point! What I have right now are 3 separate Scatters in the scene, each for one type of objects. One scatter is tiny grass with some small plants (several types of each). Scatter covers all the area and its distribution is limited only by slope (gradient map in point cloud). Second scatter is tall grass with bigger plants and they cover again all the area, only limited by slope. Same for the third scatter that contains only various trees (so basically a forest). Now when I turn on all 3 scatters, they of course fully intersect eachother so I need to somehow blend between them like a mask. Is there a way to do it? My idea would be to have for example some painted RGB texture from Photoshop, that will specify where each of these scatters will appear - red color could define where the forest scatter appears, Green where the tall grass scatter appears and Blue where the tiny grass scatter appears. This way they would not intersect eachother. I hope its understandable :lol:

Thank you for sharing the methods above and project files. Now Im starting to understand Luminance mode litle bit more. Basically I painted a grayscale map (using 3 shades of grey: black, white and middle-grey) to tell the scatterer where exactly I want each of the 3 groups to appear. And they do appear exactly there. But its still one scatter for all, which kinda limits the controls, right? Because it looks like using this Luminance mode Im not able to tell the scatterer to randomly select an object from within the group (each group has 2 objects). It always selects only one. I guess I need to use ID mode for this, right? That one is really confusing to me - I dont understand how these IDs works at all. Like where/how do I define and assign them? In this case I have only 1 scatter, fed with 3 groups, each group contains 2 objects. And I have no idea how to tell it do random selections within the group and how to make the group to appear only where the specific color on RGB map is.

Sorry for so many questions :mrgreen: I appreciate your help!
Cheers!
shadow92
 
Posts: 18
Joined: Wed Jun 13, 2018 12:46 am

Re: Scattering small vegetation: grass fields, corn fields..

Unread postby shadow92 » Sat Dec 14, 2019 7:11 pm

OK I seem to figure it out (that scatter blending thing). So basically I used textureBlend to mix 2 maps (slope gradient and for example fractal or painted map for selected area), which I tried before as well, but I did not set the blending modes correctly. Now all I have to do is use the same map and just invert it for the second scatter so they wont intersect.
shadow92
 
Posts: 18
Joined: Wed Jun 13, 2018 12:46 am

Re: Scattering small vegetation: grass fields, corn fields..

Unread postby esmith » Mon Dec 16, 2019 8:46 pm

Your starting to get the sanbox'ness of it all. You should know that if you scatter a GROUP, Clarisse will randomly pick an object from that group to scatter. Scatter ID is similar to Luminance in some cases in that it will read data from a B value.

Here is a the documentation
https://www.clarissewiki.com/4.0/geomet ... ibute.html

And I've attached a simple test file showing you one way to use this. Using the groups though, this is how you tell the scatterer that at THIS position in the list....maybe you have a group called "Tall Trees" and it's a library of tall trees...this will then pick randomly out of that group. As you can see here, 2 groups, 1 each with a red ball/box and a yellow ball/box.

ID 1 and 2 set in the scatterer, and the value on the fractal in the B attribute (Brightness, not Blue :-) ) is 1 for "white" and 2 for "black"

Capture2.JPG


Capture.JPG
Attachments
ScatterID.project
(44.54 KiB) Downloaded 55 times
User avatar
esmith
 
Posts: 168
Joined: Mon May 22, 2017 4:11 pm

Re: Scattering small vegetation: grass fields, corn fields..

Unread postby shadow92 » Mon Dec 16, 2019 10:15 pm

Thank you Eric, now its making sense! But what in case you want to use more groups, therefore more colors? Because with noise it seems like you are always limited to just 2 colors, unless you blend more fractals into one output, right? Imported texture is always clamped between 0-1 values. I tried importing painted RGB map from Photoshop and remap its R, G and B values to 1, 2 and 3, but without effect.

And second question I have is, though a bit OT, but still related to the scattering - Im using that gradient to limit the slope and would like to add some imperfections to that blend. Is there a way how to break-up gradient smoothness? With a noise for example? I mean it in a way that, say fractal noise will affect only values from absolute black to first shades of gray of that gradient, not lashing through everything like in a multiply mode. Because like that it does a brakup, yeah, but like totally everywhere and not just around that blend.
shadow92
 
Posts: 18
Joined: Wed Jun 13, 2018 12:46 am

Previous

Return to General Discussion