Generating isometric 2.5d tile map

I'm new in unity. I'm trying to create tile map in c# script. I'm creating mesh with material and assign to it procedurally generated texture. I'm use GetPixels and SetPixels for creating big texture by small rhombus tiles with alpha channel. How can i ignore transparent pixels and don't set them to big texture? Is it possible to use something like mask when i use SetPixels on texture, or may be exist better way to create tile map?

 void CreateTexture() {
         int tex_width = (int)mesh_width;
         int tex_height = (int)mesh_height;
         Color[] pixel_colors = sourceTex.GetPixels (0, 0, sourceTex.width, sourceTex.height);
         Texture2D texture = new Texture2D (tex_width, tex_height);
         for (int y = 0; y < 10; y++) {
             for (int x = 0; x < 10; x++) {
                 texture.SetPixels (0, 0, sourceTex.width, sourceTex.height, pixel_colors);
                 texture.SetPixels (37, 19, sourceTex.width, sourceTex.height, pixel_colors);
             }
         }
         texture.Apply ();
         MeshRenderer mesh_renderer = GetComponent<MeshRenderer> ();
         mesh_renderer.sharedMaterials[0].mainTexture = texture;
     }

Result:

Tile: