Unity中射线检测（Raycast）无法稳定命中目标问题求助——基于OnTriggerEnter实现弹跳抛射体异常排查

First off, let's address the most critical mistake in your code: you're passing a world position as the direction parameter to Physics.Raycast, but that method expects a direction vector (a vector pointing from the origin to where you want to cast). That's why your ray behaves unpredictably across different surfaces.

Why Your Current Code Fails #

When you use other.ClosestPoint(transform.position), you get a point in world space on the surface of the other collider. But Physics.Raycast's second argument needs to be a vector representing the ray's direction, not a point. Instead of pointing toward the collider's surface, your ray was shooting off to an arbitrary world position—explaining why it misses the ground and one side of the wall.

Step 1: Fix the Raycast Direction #

First, calculate the correct direction vector by subtracting your projectile's position from the closest point, then normalize it to ensure it's a unit vector:

Vector3 closestPoint = other.ClosestPoint(transform.position);
Vector3 rayDirection = (closestPoint - transform.position).normalized;

Step 2: Handle Trigger Overlap #

Since your projectile has Is Trigger enabled, OnTriggerEnter fires when the projectile is already overlapping with the other collider. By default, Physics.Raycast ignores colliders that the ray's origin is inside of. To fix this, offset the ray's origin slightly to start just outside the collider, and use QueryTriggerInteraction to ensure detection even when overlapping.

Here's a corrected version of your method:

private void OnTriggerEnter(Collider other) { 
    // Calculate correct direction to the closest surface point
    Vector3 closestPoint = other.ClosestPoint(transform.position);
    Vector3 rayDirection = (closestPoint - transform.position).normalized;
    
    // Offset origin to avoid starting inside the collider
    Vector3 rayOrigin = transform.position - rayDirection * 0.01f;
    
    RaycastHit hit;
    // Ensure we detect the collider even when overlapping
    if (Physics.Raycast(rayOrigin, rayDirection, out hit, Mathf.Infinity, ~0, QueryTriggerInteraction.Collide)) {
        // Calculate and apply reflection direction
        Vector3 reflectedDirection = Vector3.Reflect(transform.forward, hit.normal);
        transform.forward = reflectedDirection;
        
        // Debug visuals (keep for troubleshooting)
        Debug.DrawRay(rayOrigin, rayDirection * 2f, Color.red, 1f);
        Debug.DrawRay(hit.point, reflectedDirection * 2f, Color.green, 1f);
    }
}

Additional Tips for Reliability #

• Layer Masks: Use a layer mask to only cast rays against surfaces you want to bounce off of (e.g., LayerMask.GetMask("Ground", "Walls")). This prevents accidental hits on non-bounceable trigger objects like collectibles.
• Always Validate Hits: Wrap your Raycast in an if statement to avoid using hit.normal when no hit is detected—this prevents null reference errors or unexpected behavior.
• Alternative: Compute Penetration: For trigger overlaps, Physics.ComputePenetration can be more reliable than Raycast. It calculates the direction to push the projectile out of the collider, and you can use the resulting normal for reflection.

Why This Fixes Your Scenarios #

• Ground Cube: The corrected direction ensures the ray points directly toward the ground's surface from the projectile's position, eliminating misses caused by incorrect ray orientation.
• Wall Cube Sides: The ray now always targets the closest surface point, regardless of which side of the wall the projectile hits, fixing the one-sided miss issue.

Content of the question originates from Stack Exchange, question author Giovanni Grana