Autodesk Forge 2D Viewer：线条起止点获取、2D转3D坐标及自定义线条替换

Hey there, let's break down your problems and walk through actionable solutions for each part:

1. How to Get Start/End Points & Geometric Data of Line/Spine #

The exact approach depends on the framework you're using (like Unity, Three.js, etc.), but here are common methods for the most popular tools:

For Line Renderers (e.g., Unity's LineRenderer) #

If you're working with a standard LineRenderer component, extracting its points is straightforward:

• First, reference the LineRenderer component on your model object. Make sure to include disabled components if needed using GetComponentInChildren<LineRenderer>(true).
• Use the GetPositions() method to retrieve all Vector3 points along the line:

  LineRenderer line = GetComponent<LineRenderer>();
  Vector3[] linePoints = new Vector3[line.positionCount];
  line.GetPositions(linePoints);
  
  // Get start and end points
  Vector3 startPoint = linePoints[0];
  Vector3 endPoint = linePoints[linePoints.Length - 1];
  

• If the line uses world space vs. local space, adjust with Transform.TransformPoint() or Transform.InverseTransformPoint() as needed.

For Spine Skeleton Lines #

If you're dealing with a Spine-generated line/spine attachment:

• Access the Spine Skeleton component, then find the relevant Slot and PathAttachment:

  SkeletonAnimation skeletonAnim = GetComponent<SkeletonAnimation>();
  Slot lineSlot = skeletonAnim.Skeleton.FindSlot("your-line-slot-name");
  PathAttachment linePath = lineSlot.Attachment as PathAttachment;
  
  if (linePath != null) {
      // Get raw vertex data (convert to Vector3 using skeleton's world transform)
      float[] rawVertices = linePath.Vertices;
      List<Vector3> worldPoints = new List<Vector3>();
      for (int i = 0; i < rawVertices.Length; i += 2) {
          Vector2 localPoint = new Vector2(rawVertices[i], rawVertices[i+1]);
          Vector3 worldPoint = skeletonAnim.transform.TransformPoint(localPoint);
          worldPoints.Add(worldPoint);
      }
      
      // Start and end points are the first and last entries in worldPoints
  }
  

• Note: Spine's path data is often in local skeleton space, so you'll need to convert it to world space using the skeleton's transform.

2. Replacing the Line with Geometry in 2D View #

Replacing a line with a custom 2D geometry (like a filled shape or sprite) works by generating a mesh that follows the line's path. Here's a simplified workflow:

Step 1: Generate a Custom Mesh Along the Line #

Using the line points you extracted earlier, create a mesh that forms a "strip" along the line:

• Calculate the direction vector of each line segment.
• Create perpendicular vectors to define the width of your geometry.
• Build a list of vertices that form the top and bottom edges of the strip.
• Assign triangles to connect the vertices into a filled shape.

Example code snippet for Unity 2D:

public Mesh GenerateLineGeometry(Vector3[] linePoints, float lineWidth) {
    Mesh mesh = new Mesh();
    List<Vector3> vertices = new List<Vector3>();
    List<int> triangles = new List<int>();
    
    for (int i = 0; i < linePoints.Length - 1; i++) {
        Vector3 currentPoint = linePoints[i];
        Vector3 nextPoint = linePoints[i+1];
        Vector3 direction = (nextPoint - currentPoint).normalized;
        Vector3 perpendicular = new Vector3(-direction.y, direction.x, 0) * (lineWidth / 2);
        
        // Add top and bottom vertices for this segment
        vertices.Add(currentPoint + perpendicular);
        vertices.Add(currentPoint - perpendicular);
        vertices.Add(nextPoint + perpendicular);
        vertices.Add(nextPoint - perpendicular);
        
        // Add triangles to form the quad
        int vIndex = i * 4;
        triangles.Add(vIndex);
        triangles.Add(vIndex + 1);
        triangles.Add(vIndex + 2);
        triangles.Add(vIndex + 2);
        triangles.Add(vIndex + 1);
        triangles.Add(vIndex + 3);
    }
    
    mesh.vertices = vertices.ToArray();
    mesh.triangles = triangles.ToArray();
    mesh.RecalculateNormals();
    return mesh;
}

Step 2: Assign the Mesh to a 2D Object #

• Create a GameObject with a MeshFilter and MeshRenderer (use a 2D material for proper rendering).
• Assign the generated mesh to the MeshFilter.mesh property.
• Position the object to match the original line's location.

Quick Troubleshooting Tips #

• If you can't find the Line/Spine component: Double-check if it's attached to a child object, or if it's created dynamically at runtime (you'll need to access it after it's spawned).
• If points are incorrect: Verify whether the component uses local or world space coordinates, and adjust your transform logic accordingly.
• For Spine-specific issues: Ensure you're using the latest Spine runtime and referencing the correct slot/attachment names from your Spine project.

内容的提问来源于stack exchange，提问作者Ronak Shetiya