Create Custom Mesh Post-Processor

Mesh post-processor can be used to alter the geometry after the decal has been projected. This method can be used to change the vertex positions, UVs, etc.

using UnityEngine;
using ch.sycoforge.Decal.Projectors.Geometry;

public class CustomProcessor : IMeshProcessor 
{
    public void Process(IMesh mesh)
    {
        // Iterate over triangles
        for (int i = 0; i < mesh.TriangleIndices.Count - 3; i += 3)
        {
            int t1 = mesh.TriangleIndices[i];
            int t2 = mesh.TriangleIndices[i + 1];
            int t3 = mesh.TriangleIndices[i + 2];

            Vector3 a = mesh.Vertices[t1];
            Vector3 b = mesh.Vertices[t2];
            Vector3 c = mesh.Vertices[t3];

            Vector3 ab = b - a;
            Vector3 ac = c - a;

            // Make something with data
        
        }
    }
}

Each custom processor needs to implement the IMeshProcessor interface.

CustomProcessor processor = new CustomProcessor();
...
EasyDecal decal = EasyDecal.ProjectAt(DecalPrefab.gameObject, parent, position, averageNormal);
decal.MeshProcessors.Add(processor);

The custom processor can be hooked to the decal instance as shown in the snippet above.