I think I should structure this question better.

My terrain consists in a serie of voxel chunks procedurally generated. I then connect surface voxels to create meshes. Since it is all dynamic I cannot work on blending via the unity editor and have to do all the work via scripts and shaders.
In the following picture you can see the result achieved at the moment.

as you can notice, the area is divided into squares (which actually are cubes with a mesh inside). For every square is dynamically randomly assigned a Material (grass or sand). Both material are for simplicity going with 3 textures: the main texture (grass or sand) and rock and gravel which are used to blend the grass (or sand) depending on the slope.
As shown in the picture, blending among textures (grass -> gravel -> rock or sand -> gravel -> rock) is performed nicely, although this works only inside a single mesh.
Nevertheless I don't know how to have a smooth passage when I cross mesh having 2 different material one next to another.

The question could look like:  how can I have a smooth passage between 2 different materials, knowing that those materials don't belong to the same mesh?

I think I should structure this question better.

I'm developing a procedural terrain structured with voxel chunks.

Every chunk:

• contains a NxNxN voxel array generated with perlin noise 3d
• contains a Mesh derived from the surface points of the voxel array
• is rendered with marching cubes algoritm

Every mesh has its own Material

Every Material is made of 3 texture: one main texture and 2 minor textures to be blended with the main one depending on the slope. Every material has its own shader attached.

So I have a terrain made of a certain number of chunks, that are a certain number of meshes generated as the game launches. Inside every chunk blending if okay, since I have the only material for the current mesh I have only to blend its textures depending on heights - and this is done by the shader.

In this attached image

you can see quite clearly what I acheived until now. As you can see, everything is mostly divided in "squares", which are the meshes. Each square has a texture green or beige (grass or sand).

My concern is that: When passing from grass to sand there is no blending, i.e. blending between 2 meshes is my real problem, because inside the shader if have the surf function which iterates over all the input vertices. But those vertices are only from one mesh. To blend correctly I would need informations also about the vertices of the mesh nearby.

So the question is:  how can I blend properly materials belonging to different meshes?

UPDATE START

My understandings concerning shaders in unity: through struct Input{} it may gather mesh information via the Render.Mesh properties of the gameObject. Like if I write:

mesh.Color = someColor; 

then in the shader I can have:

struct Input { myRGB_ : COLOR } 

and then I can access inside the shader what I defined elsewhere for the Color prperty.
I think Color is just one possibility. But I don't really understand how it works: maybe unity knows which are the mesh property types and when you define a variale of the correct type in the shader it directly import data from mesh? I'm having an hard time finding out by myself..

My thought in these last 2 days was that if I could store some information about surrounding meshes, maybe I can later (in the shader) access them to make proper blending between two meshes. Am I out of my mind already?

UPDATE END

Developing a procedural terrain, in Unity4.3.4, I'm stuck in an annoying situation, here described.

At the moment I have 32x32 meshes each one with its own material. Every material is made up of 3 textures and there is a shader attached so that inside one mesh blending is performed correctly.

Problems come when I pass from a mesh to the one next to it, with a different material assigned. Since shader are per-material, no blend is performed between two different materials, that would mean to blend texture for material1, then blend textures for material2 and finally blend the two materials toghether. But I don't really know where to begin.

Here followes a picture to give a better idea of the situation

You can clearly see the sand square surrounded by grass in the bottom right corner of the picture. There is no blending between those two materials. That blending is my goal

I think I should structure this question better.

My terrain consists in a serie of voxel chunks procedurally generated. I then connect surface voxels to create meshes. Since it is all dynamic I cannot work on blending via the unity editor and have to do all the work via scripts and shaders.
In the following picture you can see the result achieved at the moment.

as you can notice, the area is divided into squares (which actually are cubes with a mesh inside). For every square is dynamically randomly assigned a Material (grass or sand). Both material are for simplicity going with 3 textures: the main texture (grass or sand) and rock and gravel which are used to blend the grass (or sand) depending on the slope.
As shown in the picture, blending among textures (grass -> gravel -> rock or sand -> gravel -> rock) is performed nicely, although this works only inside a single mesh.
Nevertheless I don't know how to have a smooth passage when I cross mesh having 2 different material one next to another.

The question could look like: how can I have a smooth passage between 2 different materials, knowing that those materials don't belong to the same mesh?

Developing a procedural terrain, in Unity4.3.4, I'm stuck in an annoying situation, here described.

At the moment I have 32x32 meshes each one with its own material. Every material is made up of 3 textures and there is a shader attached so that inside one mesh blending is performed correctly.

Problems come when I pass from a mesh to the one next to it, with a different material assigned. Since shader are per-material, no blend is performed between two different materials, that would mean to blend texture for material1, then blend textures for material2 and finally blend the two materials toghether. But I don't really know where to begin.

Here followes a picture to give a better idea of the situation

You can clearly see the sand square surrounded by grass in the bottom right corner of the picture. There is no blending between those two materials. That blending is my goal

UPDATE: I think I should point out that I'm not just seeking a way to blend materials from dynamic meshes, I also want to keep track of the material I'm walking on. I noticed that it is possible for a mesh to have stored an array of materials but I cannot really understand if this can be of help. I mean: maybe I can use some technique to teach the shader which verts belongs to a material and which does not?

UPDATE START

My understandings concerning shaders in unity: through struct Input{} it may gather mesh information via the Render.Mesh properties of the gameObject. Like if I write:

mesh.Color = someColor; 

then in the shader I can have:

struct Input { myRGB_ : COLOR } 

and then I can access inside the shader what I defined elsewhere for the Color prperty.
I think Color is just one possibility. But I don't really understand how it works: maybe unity knows which are the mesh property types and when you define a variale of the correct type in the shader it directly import data from mesh? I'm having an hard time finding out by myself..

My thought in these last 2 days was that if I could store some information about surrounding meshes, maybe I can later (in the shader) access them to make proper blending between two meshes. Am I out of my mind already?

UPDATE END

Developing a procedural terrain, in Unity4.3.4, I'm stuck in an annoying situation, here described.

At the moment I have 32x32 meshes each one with its own material. Every material is made up of 3 textures and there is a shader attached so that inside one mesh blending is performed correctly.

Problems come when I pass from a mesh to the one next to it, with a different material assigned. Since shader are per-material, no blend is performed between two different materials, that would mean to blend texture for material1, then blend textures for material2 and finally blend the two materials toghether. But I don't really know where to begin.

Here followes a picture to give a better idea of the situation

You can clearly see the sand square surrounded by grass in the bottom right corner of the picture. There is no blending between those two materials. That blending is my goal