arfoundation-samples/Assets/Scripts/ARFeatheredPlaneMeshVisualizer.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Experimental.XR;
using UnityEngine.XR.ARFoundation;

[RequireComponent(typeof(ARPlaneMeshVisualizer), typeof(MeshRenderer), typeof(ARPlane))]
public class ARFeatheredPlaneMeshVisualizer : MonoBehaviour
{
    [Tooltip("The width of the texture feathering (in world units).")]
    [SerializeField]
    float m_FeatheringWidth = 0.2f;

    ARPlaneMeshVisualizer m_PlaneMeshVisualizer;
    ARPlane m_ARPlane;
    Material m_FeatheredPlaneMaterial;

    private void Awake()
    {
        m_PlaneMeshVisualizer = GetComponent<ARPlaneMeshVisualizer>();
        m_ARPlane = GetComponent<ARPlane>();
        m_FeatheredPlaneMaterial = GetComponent<MeshRenderer>().material;
    }

    private void OnEnable()
    {
        m_PlaneMeshVisualizer.meshUpdated += ARPlaneMeshVisualizer_meshUpdated;
    }

    private void OnDisable()
    {
        m_PlaneMeshVisualizer.meshUpdated -= ARPlaneMeshVisualizer_meshUpdated;
    }

    private void ARPlaneMeshVisualizer_meshUpdated(ARPlaneMeshVisualizer planeMeshVisualizer)
    {
        GenerateBoundaryUVs(planeMeshVisualizer.mesh);
    }

    /// <summary>
    /// Generate UV2s to mark the boundary vertices and feathering UV coords.
    /// </summary>
    /// <remarks>
    /// The <c>ARPlaneMeshVisualizer</c> has a <c>meshUpdated</c> event that can be used to modify the generated
    /// mesh. In this case we'll add UV2s to mark the boundary vertices.
    /// This technique avoids having to generate extra vertices for the boundary. It works best when the shape is 
    /// is fairly uniform and the center vert is close to the barycentric center.
    /// </remarks>
    /// <param name="mesh">The <c>Mesh</c> generated by <c>ARPlaneMeshVisualizer</c></param>
    public void GenerateBoundaryUVs(Mesh mesh)
    {
        int vertexCount = mesh.vertexCount;

        // Reuse the list of UVs
        s_FeatheringUVs.Clear();
        if (s_FeatheringUVs.Capacity < vertexCount) { s_FeatheringUVs.Capacity = vertexCount; }

        // Figure out where the plane center is in plane-local space (it's in session-local space)
        BoundedPlane boundedPlane = m_ARPlane.boundedPlane;
        Pose planePose = boundedPlane.Pose;
        Vector3 centerInPlaneSpace = planePose.InverseTransformPosition(boundedPlane.Center);

        mesh.GetVertices(s_Vertices);

        Vector3 uv = new Vector3(0, 0, 0);

        float shortestUVMapping = float.MaxValue;

        // Assume the last vertex is the center vertex.
        for (int i = 0; i < vertexCount - 1; i++)
        {
            float vertexDist = Vector3.Distance(planePose.InverseTransformPosition(s_Vertices[i]), centerInPlaneSpace);

            // Remap the UV so that a UV of "1" marks the feathering boudary.
            // The ratio of featherBoundaryDistance/edgeDistance is the same as featherUV/edgeUV.
            // Rearrange to get the edge UV.
            float uvMapping = vertexDist / (vertexDist - m_FeatheringWidth);
            uv.x = uvMapping;

            // All the UV mappings will be different. In the shader we need to know the UV value we need to fade out by.
            // Choose the shortest UV to guarentee we fade out before the border.
            // This means the feathering widths will be slightly different, we again rely on a fairly uniform plane.
            if (shortestUVMapping > uvMapping) { shortestUVMapping = uvMapping; }

            s_FeatheringUVs.Add(uv);
        }

        m_FeatheredPlaneMaterial.SetFloat("_ShortestUVMapping", shortestUVMapping);

        // Add the center vertex UV
        uv.Set(0, 0, 0);
        s_FeatheringUVs.Add(uv);

        mesh.SetUVs(1, s_FeatheringUVs);
        mesh.UploadMeshData(false);
    }

    static List<Vector3> s_FeatheringUVs = new List<Vector3>();
    static List<Vector3> s_Vertices = new List<Vector3>();
}