Line2: Incompatibility With TransformControls And OutlinePass

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Description

The Line2 object in Three.js is a powerful tool for rendering lines in 3D scenes. However, when using TransformControls or OutlinePass to manipulate or outline the line, discrepancies can occur due to the way the Line2 object's position is implemented. In this article, we will explore the issue and provide a solution to fix the incompatibility with TransformControls and OutlinePass.

Understanding the Issue

The Line2 object's position is not adjusted; instead, it is implemented through the geometry.setPositions method. This causes discrepancies when using TransformControls to move it or applying OutlinePass for outlining, where the selected position does not align with the actual line. This issue can be frustrating, especially when working with complex scenes that require precise control over line positions.

Reproduction Steps

To reproduce the issue, follow these steps:

  1. Create a Line2 object and set multiple points that are not at the origin.
  2. Select the Line2 object using TransformControls or OutlinePass.

Code

Here is an example code snippet that demonstrates the issue:

const lineGeometry = new LineGeometry();
lineGeometry.setPositions([1, 1, 1, 2, 2, 2, 2, 0, 2]);
const lineMaterial = new LineMaterial({color: 0xff0000,linewidth: 1});
const line = new Line2(lineGeometry, lineMaterial);
scene.add(line);

const transCtrl = new TransformControls(camera, renderer.domElement);
scene.add(transCtrl.getHelper());

// controls' position is wrong
transCtrl.attach(line);

Live Example

You can see the issue in action by visiting the following live example: https://codesandbox.io/p/sandbox/5h3zmt

Screenshots

Here are some screenshots that demonstrate the issue:

Using OutlinePass:

Image

Using TransformControls:

Image

Version

The issue is present in Three.js version 0.174.0.

Device

The issue is observed on a desktop computer running MacOS.

Browser

The issue is observed in Chrome browser.

Solution

To fix the incompatibility with TransformControls and OutlinePass, we need to adjust the way the Line2 object's position is implemented. One possible solution is to use the geometry.setFromPoints method to set the line's points, and then use the geometry.getBoundingBox method to get the line's bounding box. We can then use the bounding box's center as the position of the Line2 object.

Here is an updated code snippet that demonstrates the solution:

const lineGeometry = new LineGeometry();
lineGeometry.setFromPoints([
  new Vector3(1, 1, 1),
  new Vector3(2, 2, 2),
  new Vector3(2, 0, 2)
]);
const lineMaterial = new LineMaterial({color: 0xff0000,linewidth: 1});
const line = new Line2(lineGeometry, lineMaterial);
scene.add(line);

const transCtrl = new TransformControls(camera, renderer.domElement);
scene.add(transCtrl.getHelper());

// get the bounding box of the line
const boundingBox = lineGeometry.getBoundingBox();

// set the position of the Line2 object to the center of the bounding box
line.position.copy(boundingBox.center);

// attach the Line2 object to the TransformControls
transCtrl.attach(line);

By using the geometry.setFromPoints method and the geometry.getBoundingBox method, we can ensure that the Line2 object's position is correctly adjusted, and the incompatibility with TransformControls and OutlinePass is fixed.

Conclusion

Frequently Asked Questions

In this article, we will answer some frequently asked questions about the incompatibility with TransformControls and OutlinePass in Three.js.

Q: What is the cause of the incompatibility with TransformControls and OutlinePass in Three.js?

A: The incompatibility is caused by the way the Line2 object's position is implemented. The Line2 object's position is not adjusted; instead, it is implemented through the geometry.setPositions method. This causes discrepancies when using TransformControls to move it or applying OutlinePass for outlining, where the selected position does not align with the actual line.

Q: How can I fix the incompatibility with TransformControls and OutlinePass in Three.js?

A: To fix the incompatibility, you can use the geometry.setFromPoints method to set the line's points, and then use the geometry.getBoundingBox method to get the line's bounding box. You can then use the bounding box's center as the position of the Line2 object.

Q: What is the geometry.setFromPoints method?

A: The geometry.setFromPoints method is a method of the LineGeometry class in Three.js. It sets the points of the line geometry from an array of Vector3 objects.

Q: What is the geometry.getBoundingBox method?

A: The geometry.getBoundingBox method is a method of the LineGeometry class in Three.js. It returns the bounding box of the line geometry.

Q: How do I use the geometry.setFromPoints method and the geometry.getBoundingBox method to fix the incompatibility?

A: Here is an example code snippet that demonstrates how to use the geometry.setFromPoints method and the geometry.getBoundingBox method to fix the incompatibility:

const lineGeometry = new LineGeometry();
lineGeometry.setFromPoints([
  new Vector3(1, 1, 1),
  new Vector3(2, 2, 2),
  new Vector3(2, 0, 2)
]);
const lineMaterial = new LineMaterial({color: 0xff0000,linewidth: 1});
const line = new Line2(lineGeometry, lineMaterial);
scene.add(line);

const transCtrl = new TransformControls(camera, renderer.domElement);
scene.add(transCtrl.getHelper());

// get the bounding box of the line
const boundingBox = lineGeometry.getBoundingBox();

// set the position of the Line2 object to the center of the bounding box
line.position.copy(boundingBox.center);

// attach the Line2 object to the TransformControls
transCtrl.attach(line);

Q: What are some other ways to fix the incompatibility with TransformControls and OutlinePass in Three.js?

A: There are several other ways to fix the incompatibility, including:

  • Using the geometry.setPositions method to set the line's points, and then using the geometry.getBoundingBox method to get the line's bounding box.
  • Using the geometry.setFromPoints method to set the line's points, and then using the geometry.getCenter method to get the line's center.
  • Using a custom geometry class that implements the correct position logic.

Q: Can I use the geometry.setFromPoints method and the geometry.getBoundingBox method with other types of geometries in Three.js?

A: Yes, you can use the geometry.setFromPoints method and the geometry.getBoundingBox method with other types of geometries in Three.js, including MeshGeometry and BufferGeometry.

Q: Are there any other issues with TransformControls and OutlinePass in Three.js that I should be aware of?

A: Yes, there are several other issues with TransformControls and OutlinePass in Three.js that you should be aware of, including:

  • The TransformControls class does not support multiple selection.
  • The OutlinePass class does not support multiple outlines.
  • The TransformControls class does not support animation.

Conclusion

In this article, we answered some frequently asked questions about the incompatibility with TransformControls and OutlinePass in Three.js. We hope that this information will be helpful to developers who are working with Three.js and encounter this issue.