Unity中如何检测射线投射指定网格区域是否存在凸起？

Absolutely! This is totally achievable in Unity—let’s break down two solid approaches to implement this feature, depending on your needs for precision and performance:

Approach 1: Direct Mesh Vertex Analysis (Precise) #

This method works directly with the target mesh’s vertex data to check for bumps in your defined square region.

Step 1: Grab Raycast Hit Data #

First, you’ll need to get the mesh associated with your raycast hit, plus convert the world-space hit point to the mesh’s local space for easier calculations:

RaycastHit hit;
if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit))
{
    MeshFilter meshFilter = hit.collider.GetComponent<MeshFilter>();
    if (meshFilter == null) return; // Skip if there's no mesh attached
    
    Mesh targetMesh = meshFilter.mesh;
    Vector3 hitPointLocal = hit.collider.transform.InverseTransformPoint(hit.point);
    Vector3 hitNormalLocal = hit.collider.transform.InverseTransformDirection(hit.normal);
}

Step 2: Define Your Square Region #

Set the size of your square, then calculate two orthogonal axes (U and V) perpendicular to the hit normal—these will be the "sides" of your square:

float halfSquareSize = 1f; // *Adjust this to control how big your scan area is*
// Generate U axis (perpendicular to normal)
Vector3 uAxis = Vector3.Cross(hitNormalLocal, Vector3.up);
if (uAxis.magnitude < 0.01f) uAxis = Vector3.Cross(hitNormalLocal, Vector3.right);
uAxis.Normalize();
// Generate V axis (perpendicular to both normal and U)
Vector3 vAxis = Vector3.Cross(hitNormalLocal, uAxis).Normalize();

Step 3: Check Vertices for Bumps #

Loop through the mesh’s vertices, filter those inside the square, and compare their height relative to the hit point to detect bumps:

float heightThreshold = 0.1f; // *Adjust this to set how "high" a bump needs to be to count*
bool hasBump = false;
List<Vector3> localVertices = new List<Vector3>();
targetMesh.GetVertices(localVertices);

float hitHeight = Vector3.Dot(hitPointLocal, hitNormalLocal);

foreach (Vector3 vert in localVertices)
{
    Vector3 offset = vert - hitPointLocal;
    // Check if vertex is inside the square region
    float uDistance = Vector3.Dot(offset, uAxis);
    float vDistance = Vector3.Dot(offset, vAxis);
    
    if (Mathf.Abs(uDistance) <= halfSquareSize && Mathf.Abs(vDistance) <= halfSquareSize)
    {
        float vertHeight = Vector3.Dot(vert, hitNormalLocal);
        // If vertex is higher than the hit point by more than our threshold
        if (vertHeight - hitHeight > heightThreshold)
        {
            hasBump = true;
            break; // No need to check further once we find a bump
        }
    }
}

Debug.Log(hasBump ? "Found a bump in the region!" : "No bumps detected.");

Performance Tip: If your mesh has thousands of vertices, optimize this by only checking vertices in the triangle that was hit (use hit.triangleIndex to get the relevant triangle’s vertex indices).

Approach 2: Ray Grid Scan (Simpler, No Mesh Access Needed) #

If you don’t need precise vertex-level data, this method uses a grid of rays over your square region to check for height differences. It works with any collider, even if you don’t have direct access to the mesh.

int rayGridSize = 5; // *5x5 grid of rays—increase for more precision*
float halfSquareSize = 1f;
float rayStep = (halfSquareSize * 2) / (rayGridSize - 1);
bool hasBump = false;
float heightThreshold = 0.1f;

// Generate U/V axes same as Approach 1
Vector3 uAxis = Vector3.Cross(hit.normal, Vector3.up);
if (uAxis.magnitude < 0.01f) uAxis = Vector3.Cross(hit.normal, Vector3.right);
uAxis.Normalize();
Vector3 vAxis = Vector3.Cross(hit.normal, uAxis).Normalize();

for (int i = 0; i < rayGridSize; i++)
{
    for (int j = 0; j < rayGridSize; j++)
    {
        // Calculate the origin of the current ray in world space
        Vector3 localOffset = uAxis * (-halfSquareSize + i * rayStep) + vAxis * (-halfSquareSize + j * rayStep);
        Vector3 rayOrigin = hit.collider.transform.TransformPoint(hitPointLocal + localOffset);
        Ray scanRay = new Ray(rayOrigin, hit.normal);
        
        if (Physics.Raycast(scanRay, out RaycastHit subHit, 2f))
        {
            float heightDiff = Vector3.Dot(subHit.point - hit.point, hit.normal);
            if (heightDiff > heightThreshold)
            {
                hasBump = true;
                goto EndScan; // Exit both loops early
            }
        }
    }
}
EndScan:

Debug.Log(hasBump ? "Bump detected in the scan area!" : "No bumps found.");

Both methods work great—pick the one that fits your project’s precision and performance needs!

内容的提问来源于stack exchange，提问作者Vivek Rajagopal