How can I loop through every 3D point on a plane's surface in C#?

Question

I'm making a model editor for Unity 5 that will allow the developer to draw an image, and then inflate the image into a 3D object. Of course, it would not inflate transparent points. In order to do this, I've created a script that's connected to a plane with particles/alpha blended enabled in order to ensure the plane shows both sides. I've also created a custom editor script that links to the plane's script. I decided it would be a good idea to disable the mesh renderer when the plane is inflated to ensure people can't see the deflated object. What I want to do is to loop through each Vector3 on the plane's surface and create a new object with new points based on the pixels in the object.

So the question is: How can I loop through every 3D point on a plane's surface in C#?

Bonus points if you can help me find the color of each point, but I think I have that figured out.

UPDATE:

Thanks for all the support! I actually thought of a way to do this that I'm suprised I never thought of. My idea only works well with planes, but that's all that I need. I also figured out how to filter colors! You can view the code below.

     public static IEnumerable<Vector3> GetPoints(GameObject obj, float res)
     {
         Vector3[] verts = obj.GetComponent<MeshFilter>().sharedMesh.vertices;
         float x1 = float.MaxValue;
         float x2 = 0;
         float z1 = float.MaxValue;
         float z2 = 0;
         foreach (Vector3 vert in verts)
         {
             if (vert.x < x1)
             {
                 x1 = vert.x;
             }
             if (vert.x > x2)
             {
                 x2 = vert.x;
             }
             if (vert.z < z1)
             {
                 z1 = vert.z;
             }
             if (vert.z > z2)
             {
                 z2 = vert.z;
             }
         }
         Vector2 size = new Vector2(Mathf.Abs(x1 - x2), Mathf.Abs(z1 - z2));
         Texture2D tex = ((Texture2D)obj.GetComponent<Renderer>().sharedMaterial.mainTexture);
         for (float x = -(size.x / 2); x <= size.x / 2; x += res)
         {
             for (float z = -(size.y / 2); z <= size.y / 2; z += res)
             {
                 Vector3 V3 = obj.transform.TransformPoint(new Vector3(x, 1, z));
                 if (tex.GetPixel(tex.width - (int)(((x + (size.x / 2)) / size.x) * tex.width), 
                 tex.height - (int)(((z + (size.y / 2)) / size.y) * tex.height)).a > 0.5f)
                 yield return V3;
             }
         }
     }

If anyone is wondering how to use the code above, here's a snipplet (0.1f is the increment):

 foreach (Vector3 V3 in GetPoints(gameObject, 0.1f))
 {
     GameObject t = Instantiate(gameObject2);
     t.transform.position = V3;
 }

Here's a couple screenshots of what you can do:

alt text

Answer 1

Best Answer

Answer by Glurth · Jul 26, 2016 at 04:55 PM

You mentioned that you now know how to get each vertex of the MeshFilter's mesh. These verticies are defined in model-space. In order to convert these to world-space coordinates use the MeshFilter's transform. e.g.

 worldVertexPoint=meshfilter.gameobject.transform.TransformPoint(modelVertexPoint);

You could now put an object at that particular worldVertexPoint like so:

 someObject.transform.position= worldVertexPoint;

https://docs.unity3d.com/ScriptReference/Transform.TransformPoint.html

Regarding getting the color of the texture, at that vertex: Lets go back a step- lets say you got your vertex using

 modelVertexPoint= mesh.vertices[vertexNumber];

We can also get the Texture coordinate (UV), of that vertexNumber

 Vector2 vertexUV = mesh.uv[vertexNumber];

You can then feed this UV coordinate, into the GetPixel function that MrPMorris mentioned.
The advantage to this method is, it eliminates the need to do any raycasting. It does NOT account for any shadows or lighting though.

note: Colored verticies are optional in a Mesh, and they require a vertex-color-shader to work. Fairly rare nowadays. If you import the mesh it might not have vertex colors defined. If you ARE using colored verticies , rather than a texture, it's even simpler:

 Color vertexColors= mesh.color[vertexNumber];

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hkarrson · Jul 26, 2016 at 05:01 PM 0

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Thank you so much! I'll give it a shot!

hkarrson · Jul 26, 2016 at 05:12 PM 0

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Thanks a lot! That helped a ton! 10 points goes to you!

Glurth hkarrson · Jul 26, 2016 at 05:20 PM 0

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No additional points needed, thanks tho! Accepting it as the answer will grant me points anyway :) What about the color stuff? Get that figured out? Are you using vertex colors(in which case, you now have the answer) or textures?

hkarrson Glurth · Jul 26, 2016 at 05:22 PM 0

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No problem! Unfortunately, mesh.color32 is returning an empty list. It would be great if you could help me figure that out :)

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hkarrson · Jul 26, 2016 at 05:58 PM 0

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Thanks to you, I was able to retrieve some of the pixels, but is it possible to get the same number of vertices as the number of pixels in the image?

Thanks!

Glurth hkarrson · Jul 26, 2016 at 06:20 PM 0

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Not with any of the methods I've described, no. It's starting to sound like what you want is a surface shader. A surface-shader performs processing on each pixel of a drawn object. If you are just looking for a random pixel, here and there, then $$anonymous$$rP$$anonymous$$orris's raycast suggestion might be suitable.

hkarrson Glurth · Jul 26, 2016 at 06:30 PM 0

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Thanks for the reply. Could a surface shader send information back to c# so that it may be processed later?

EDIT: I just found out that what I just asked is totally possible. Thank you SO $$anonymous$$UCH! I now know what to do. :)

How can I loop through every 3D point on a plane's surface in C#?

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