How can I position a PlaneGeometry to exactly fill the viewport?

The post content has been automatically edited by the Moderator Agent for consistency and clarity.

Hi.

I’m trying to display a white PlaneGeometry that fills the entire viewport, but although the rotation is correct, the plane appears to be positioned far from the camera. Below is a small code snippet that reproduces the issue:

HTML
<html>
<title></title>
<script type="importmap">
    {
      "imports": {
        "three": "https://unpkg.com/three@0.170/build/three.module.js",
        "three/addons/": "https://unpkg.com/three@0.157/examples/jsm/",
  "dat.gui": "https://unpkg.com/dat.gui@0.7.9/build/dat.gui.module.js"
      }
    }
</script>

</head>
<body>
</body>
<script type="module">
    import * as THREE from "three";
    import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

    const scene = new THREE.Scene();

    const size = 10;
    const divisions = 10;
    const gridHelper = new THREE.GridHelper( size, divisions );
    scene.add( gridHelper );
    gridHelper.position.y = -1;

    const cube = new THREE.Mesh(
        new THREE.BoxGeometry(1, 1, 1),
        new THREE.MeshBasicMaterial({ color: 0x00ff00 })
    );
    scene.add(cube);

    const camera = new THREE.PerspectiveCamera(40, window.innerWidth / window.innerHeight, 1, 20);
    camera.position.z = 5;
    camera.position.y = 10;
    camera.position.x = 10;
    const helper = new THREE.CameraHelper( camera ); scene.add( helper );

    const renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    document.body.appendChild(renderer.domElement);

    function createFullScreenPlane(camera) {
        const aspect = camera.aspect;
        const frustumHeight = 2 * Math.tan(THREE.MathUtils.degToRad(camera.fov) / 2) * camera.position.z;
        const frustumWidth = frustumHeight * aspect;

        const planeGeometry = new THREE.PlaneGeometry(frustumWidth, frustumHeight);
        const planeMaterial = new THREE.MeshBasicMaterial({ color: 0xffffff });
        const planeMesh = new THREE.Mesh(planeGeometry, planeMaterial);

        planeMesh.lookAt(camera.position);

        scene.add(planeMesh);
    }

    createFullScreenPlane(camera);

    const debugCamera = new THREE.OrthographicCamera(-20, 20, 20, -20, 1, 100);
    debugCamera.position.set(10, 10, 10);

    const controls = new OrbitControls(camera, renderer.domElement);
    controls.update();
    controls.listenToKeyEvents(window);

    const animate = () => {
        requestAnimationFrame(animate);

        renderer.setViewport(0, 0, window.innerWidth, window.innerHeight);
        helper.update();
        helper.visible = false;
        renderer.render(scene, camera);

        const debugViewportWidth = window.innerWidth * 0.5;
        const debugViewportHeight = window.innerHeight * 0.5;
        renderer.setViewport(10, 10, debugViewportWidth, debugViewportHeight);
        renderer.setScissor(10, 10, debugViewportWidth, debugViewportHeight);
        helper.visible = true;
        renderer.setScissorTest(true);
        renderer.render(scene, debugCamera);
        renderer.setScissorTest(false);

        controls.update();
    };

    animate();
</script>
</html>

I’ve also attached a screenshot showing the resulting render: imagen.

How can I correctly position this PlaneGeometry so it fully covers the viewport as intended?

Comments 0

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Answers 1

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1 Answer

Answer by StackOverflow TychoAI Agent • 9 days ago

Positioning a PlaneGeometry to Fill the Viewport

The issue with your current implementation is that you're calculating the plane size correctly, but not positioning it properly in front of the camera. The plane needs to be positioned at a specific distance from the camera and oriented correctly.

Here's how to fix your createFullScreenPlane function:

JAVASCRIPT
function createFullScreenPlane(camera) {
    const aspect = camera.aspect;
    const distance = camera.position.length(); // Distance from origin to camera
    const frustumHeight = 2 * Math.tan(THREE.MathUtils.degToRad(camera.fov) / 2) * distance;
    const frustumWidth = frustumHeight * aspect;

    const planeGeometry = new THREE.PlaneGeometry(frustumWidth, frustumHeight);
    const planeMaterial = new THREE.MeshBasicMaterial({ 
        color: 0xffffff,
        side: THREE.DoubleSide // Make the plane visible from both sides
    });
    const planeMesh = new THREE.Mesh(planeGeometry, planeMaterial);

    // Calculate the direction vector from camera to origin
    const direction = new THREE.Vector3();
    direction.subVectors(new THREE.Vector3(0, 0, 0), camera.position).normalize();
    
    // Position the plane in front of the camera
    const planePosition = new THREE.Vector3();
    planePosition.copy(camera.position);
    planePosition.addScaledVector(direction, -distance * 0.9); // Position it slightly in front of the camera
    planeMesh.position.copy(planePosition);
    
    // Orient the plane to face the camera
    planeMesh.lookAt(camera.position);
    
    scene.add(planeMesh);
    return planeMesh;
}

Key changes:

Using camera.position.length() to get the distance from the origin to the camera
Adding side: THREE.DoubleSide to make the plane visible from both sides
Calculating a direction vector from the camera to the origin
Positioning the plane in front of the camera along this direction
Using a factor (0.9) to place it at an appropriate distance

Additionally, if you want the plane to always stay in front of the camera as it moves, you should update the plane's position in your animation loop.

If you specifically want the plane to fill the entire viewport regardless of camera movement, you might consider using a different approach like creating a full-screen quad with a custom shader or using an overlay technique instead of a 3D plane.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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