Terrain 'Grass' Detail Mesh, Blender, and Vertex Color Alpha problem

Hello,

I am currently working with the unity terrain engine, and am applying grass meshes (as detail meshes, rendered as 'grass') I have modeled within blender. Everything is working fine, until I turn on the terrain wind and see my grass floating a great distance from it's original position, not staying anchored to the terrain.

I have done some reading on the subject and have found that Unity uses a mesh's Vertex Color Alpha to determine where / how wind forces are applied? So I would need to have an opaque value at the bottom of the mesh (to anchor the position), and gradually go transparent towards the top to apply wind force?

This makes things difficult for me as I've found no way to modify and export a blender mesh's Vertex Color Alpha into unity....

Any blender users find a work around for this problem yet?

 

Have you seen that Terrain tutorial? I am not entirely sure if it answers your question.

 

Thanks for the reply Dantus,

Yep, I've seen that tutorial. It describes placement of grass detail mesh, but doesn't cover the wind problem I'm experiencing. The detail mesh grass I am placing is moving several feet away from the origin point when terrain wind is applied. I'm reasonably certain this can be solved by applying certain vertex color alpha values to my mesh, but as far as I can tell blender does not allow for that. So I'm a bit stuck

 

Do you need the rgb color of the vertices for something else? An option would be to implement an importer for Unity that converts the rgb into an alpha value.

 

No I don't, that would be a viable option in my case. How would I go about implementing an importer to do that?

 

While looking for a solution I came across this:
http://answers.unity3d.com/questions/172835/texture-blending-shader-using-vertex-coloring-with.html

Getting Blender to export an object's vertex rgb as an alpha would be more useful than importing I think?

In any case, I attempted to apply the code posted in the link above, and unity's console spat out an error when importing the .blend file:

Back to researching!

 

My idea is basically that you don't have to modify this file. If you import a .blend file, it automatically performs that modification, but within Unity. I'll have a look at it.

 

I made a quick script. It's untested!!!
It takes the vertex color and applies the avarage value to the alpha channel of the vertex color.

You have to do the following to get it working:
- Import the attached package.
- The .blend with the grass must contain 'vcta' in the file name.
- Maybe you have to reimport the .blend file.

And it should work...

EDIT: It does not work!!! Download the package from the next post!

 

Had some time to test it on my own and it did not work
Attached is a working version.

What you need to do is:
- Import the attached package.
- The .blend with the grass must contain 'vcta' in the file name.
- As you paint the vertices in Blender (Vertex Paint):
-> Black means is not influenced by the wind
-> White means is moved by wind

 

Sorry for the late reply,

I just gave your script a try and it works like a charm! My grass mesh is no longer floating around! Thank you very much!

 

Thanks much for this solution! This works in Unity 4.6.1.
A few notes that might help Blender users:
If your detail does not show up on the terrain, check under the terrain it might be there.
To correct this, I set my 3D cursor at the top of my mesh then hit CTRL ALT SHIFT C, then select 'Origin to 3D cursor'.
Also I seem to be having an upside down issue. In vertex paint mode, I painted the top vertices black and the bottom ones white. In Blender this appears to make the top darker and the bottom lighter while still showing the texture png I had attached. In Unity this gradient does not show.
-Import Dantus' file into Unity,
-Save your .blend file something like grassvcta.blend
-In Blender(2.73) go to vertex paint mode (same place you select Object mode or Edit Mode)
-Paint the top black and the bottom white (or visa-versa,experiment)
-with more complex mesh, you may need to blend the gradient along your vertices.
-In Unity, each time you save a new .blend, Edit>Remove your old mesh detail and create a new one or you changes might not show up.
-In my Unity Asset folder I made a folder called Blender where I save all my .blend files. In the Blender folder I save materials to a folder called Materials.

 

@Dantus
I've checked this script on Unity 5.6.0f3 and it's working perfectly
Thanks, it really helps You basically saved our development process.