Can we accurately pinpoint individual LineSegments in three.js by hovering over them, especially those with unique geometries?

Question

Can we accurately pinpoint individual LineSegments in three.js by hovering over them, especially those with unique geometries?

Creating two examples of drawing lines in three.js was quite a fun challenge. One example showcased different geometry and material, while the other kept it simple with just one geometry and material. The demonstration links can be found here: Example 1 and Example 2.

In example 1, I enjoyed hovering over the lines to see the material color change on mouseover. However, in example 2, the whole lineMesh changed its color when hovered since there was only one material.

Now I'm intrigued by the thought of using just one geometry like in example 2, but still achieving the distinct hover effect seen in example 1 with multiple LineSegment pieces. Is this even possible?

An important consideration for me is that using multiple geometry seems to slow down the browser significantly, especially when rendering large models with numerous members. As I plan to incorporate multiple three.js models in different div elements on a page, I am concerned about the overall performance impact on the browser.

javascript three.js

Answer 1

Answer №1

Utilizing THREE.BufferGeometry(), THREE.LineSegments(), and setting

.vertexColors = THREE.VertexColors

:

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 1, 1000);
camera.position.set(0, 0, 10);
var renderer = new THREE.WebGLRenderer({
  antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

// Define points for creating the geometry
var points = [
  new THREE.Vector3(-5, 5, 0),
  new THREE.Vector3(),
  new THREE.Vector3(),
  new THREE.Vector3(5, 5, 0),
  new THREE.Vector3(5, 5, 0),
  new THREE.Vector3(5, -5, 0)
];

// Create buffer geometry and set color attributes
var geom = new THREE.BufferGeometry().setFromPoints(points);
geom.addAttribute("color", new THREE.BufferAttribute(new Float32Array([/* colors */]), 3));
geom.addAttribute("colorBase", new THREE.BufferAttribute(new Float32Array([/* original colors */]), 3));

// Define material with vertex colors enabled
var mat = new THREE.LineBasicMaterial({
  vertexColors: THREE.VertexColors
});

// Create line segments and add to scene
var line = new THREE.LineSegments(geom, mat);
scene.add(line);

// Additional variables for interactivity and color manipulation
var raycaster = new THREE.Raycaster();
var mouse = new THREE.Vector2();
var intersects = [];
var oldIndex = -1;
var col = new THREE.Color();

// Event listener for mouse movement
window.addEventListener("mousemove", onMouseMove, false);

function onMouseMove(event) {
  // Update mouse position
}

// Helper function to highlight segment on hover
function highlightSegment(idx, color) {
  // Change color of segment
}

// Function to change color of a segment
function setColor(idx, color) {
  // Logic for changing color
}

// Restore original color of a segment
function restoreColor() {
  // Reset color to original value
}

// Render loop
render();

function render() {
  requestAnimationFrame(render);
  renderer.render(scene, camera);
}

body {
  overflow: hidden;
  margin: 0;
}

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c8bca0baAdad88f8e6f9fafae6f8">[email protected]</a>/build/three.min.js"></script>

Answer 2

Utilizing THREE.BufferGeometry(), THREE.LineSegments(), and setting

.vertexColors = THREE.VertexColors

:

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 1, 1000);
camera.position.set(0, 0, 10);
var renderer = new THREE.WebGLRenderer({
  antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

// Define points for creating the geometry
var points = [
  new THREE.Vector3(-5, 5, 0),
  new THREE.Vector3(),
  new THREE.Vector3(),
  new THREE.Vector3(5, 5, 0),
  new THREE.Vector3(5, 5, 0),
  new THREE.Vector3(5, -5, 0)
];

// Create buffer geometry and set color attributes
var geom = new THREE.BufferGeometry().setFromPoints(points);
geom.addAttribute("color", new THREE.BufferAttribute(new Float32Array([/* colors */]), 3));
geom.addAttribute("colorBase", new THREE.BufferAttribute(new Float32Array([/* original colors */]), 3));

// Define material with vertex colors enabled
var mat = new THREE.LineBasicMaterial({
  vertexColors: THREE.VertexColors
});

// Create line segments and add to scene
var line = new THREE.LineSegments(geom, mat);
scene.add(line);

// Additional variables for interactivity and color manipulation
var raycaster = new THREE.Raycaster();
var mouse = new THREE.Vector2();
var intersects = [];
var oldIndex = -1;
var col = new THREE.Color();

// Event listener for mouse movement
window.addEventListener("mousemove", onMouseMove, false);

function onMouseMove(event) {
  // Update mouse position
}

// Helper function to highlight segment on hover
function highlightSegment(idx, color) {
  // Change color of segment
}

// Function to change color of a segment
function setColor(idx, color) {
  // Logic for changing color
}

// Restore original color of a segment
function restoreColor() {
  // Reset color to original value
}

// Render loop
render();

function render() {
  requestAnimationFrame(render);
  renderer.render(scene, camera);
}

body {
  overflow: hidden;
  margin: 0;
}

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c8bca0baAdad88f8e6f9fafae6f8">[email protected]</a>/build/three.min.js"></script>

Answer 3

Answer №2

To achieve the desired effect, it is important to utilize vertex colors rather than relying solely on material colors. Here's how you can implement this:

var lineMaterial = new THREE.LineBasicMaterial({ vertexColors: THREE.VertexColors});

Each vertex should have its corresponding color pushed. For example:

geometry.colors.push(new THREE.Color("rgb(0, 0, 255)"), new THREE.Color("rgb(0, 0, 255)"));

In the mouse hover handler, you must retrieve the index of the intersected line and modify the color of that specific vertex like so:

intersects[0].object.geometry.colors[intersects[0].index].setHex(0xff0000);

let nextIndex = intersects[0].index + (intersects[0].index % 2 == 0 ? 1 : -1 );
intersects[0].object.geometry.colors[nextIndex].setHex(0xff0000);
intersects[0].object.geometry.colorsNeedUpdate = true;

Here's a simplified version based on your second approach:

     var container, scene, camera, renderer;
        var mouse = new THREE.Vector2();
        var intersected;

        // Initialization function
        function init() {
            /* Code snippet for initialization */
        }

        // Animation loop function
        function animate() {
            /* Code snippet for animation loop */
        }

        // Mouse move event handler
        function onMouseMove(event) {
            /* Code snippet for handling mouse movement */
        }

        // Rendering function
        function render() {
            /* Code snippet for rendering the scene */
        }
        
        // Add event listener for mouse movements
        container.addEventListener('mousemove', onMouseMove, false);

For an alternative method to the raycaster, GPU picking can be utilized to determine the intersected line.

Answer 4

To achieve the desired effect, it is important to utilize vertex colors rather than relying solely on material colors. Here's how you can implement this:

var lineMaterial = new THREE.LineBasicMaterial({ vertexColors: THREE.VertexColors});

Each vertex should have its corresponding color pushed. For example:

geometry.colors.push(new THREE.Color("rgb(0, 0, 255)"), new THREE.Color("rgb(0, 0, 255)"));

In the mouse hover handler, you must retrieve the index of the intersected line and modify the color of that specific vertex like so:

intersects[0].object.geometry.colors[intersects[0].index].setHex(0xff0000);

let nextIndex = intersects[0].index + (intersects[0].index % 2 == 0 ? 1 : -1 );
intersects[0].object.geometry.colors[nextIndex].setHex(0xff0000);
intersects[0].object.geometry.colorsNeedUpdate = true;

Here's a simplified version based on your second approach:

     var container, scene, camera, renderer;
        var mouse = new THREE.Vector2();
        var intersected;

        // Initialization function
        function init() {
            /* Code snippet for initialization */
        }

        // Animation loop function
        function animate() {
            /* Code snippet for animation loop */
        }

        // Mouse move event handler
        function onMouseMove(event) {
            /* Code snippet for handling mouse movement */
        }

        // Rendering function
        function render() {
            /* Code snippet for rendering the scene */
        }
        
        // Add event listener for mouse movements
        container.addEventListener('mousemove', onMouseMove, false);

For an alternative method to the raycaster, GPU picking can be utilized to determine the intersected line.

Answer 5

Answer №3

If you want to change the appearance of a LineSegment using a single geometry, one workaround is to overlay an additional LineSegment dynamically on top of the segment you wish to highlight. This method should help create the desired visual effect you seek.

To implement this solution, you can generate a new material without utilizing depthTest:

material.depthTest=false

By doing so, the added LineSegment will always display above any geometries with materials featuring depthTest functionality.

Answer 6

If you want to change the appearance of a LineSegment using a single geometry, one workaround is to overlay an additional LineSegment dynamically on top of the segment you wish to highlight. This method should help create the desired visual effect you seek.

To implement this solution, you can generate a new material without utilizing depthTest:

material.depthTest=false

By doing so, the added LineSegment will always display above any geometries with materials featuring depthTest functionality.

Can we accurately pinpoint individual LineSegments in three.js by hovering over them, especially those with unique geometries?

Answer №1

Answer №2

Answer №3

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