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@ayamflow
Last active May 15, 2024 12:37
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Threejs Fit plane to screen
var cameraZ = camera.position.z;
var planeZ = 5;
var distance = cameraZ - planeZ;
var aspect = viewWidth / viewHeight;
var vFov = camera.fov * Math.PI / 180;
var planeHeightAtDistance = 2 * Math.tan(vFov / 2) * distance;
var planeWidthAtDistance = planeHeightAtDistance * aspect;
// or
let dist = camera.position.z - mesh.position.z;
let height = ... // desired height to fit
camera.fov = 2 * Math.atan(height / (2 * dist)) * (180 / Math.PI);
camera.updateProjectionMatrix();
// Basically solving an AAS triangle https://www.mathsisfun.com/algebra/trig-solving-aas-triangles.html
https://i.stack.imgur.com/PgSn3.jpg
@vlucendo
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Very handy, I was looking for this 👍

@vin-ni
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vin-ni commented Jul 10, 2019

thank you!

@nicoptere
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thanks poussin ! 🥇

@seriusokhatsky
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Thank you!

@kevinboudot
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Merci copain ! <3

@thibka
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thibka commented Aug 23, 2020

Thanks!

@jade-itworkswhy
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Great, thank you!

@mikatalk
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Excellent, merci! 🌟

@manudurgoni
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Merci chouchou <3

@julapy
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julapy commented Dec 23, 2022

here is another approach, changing the position and rotation of the plane to always fit the screen.

  const fitPlaneToScreen = (planeMesh, planeHeight) => {
    let aspect = window.innerHeight / window.innerWidth;
    if( aspect < 1.0 ) {
      planeHeight *= aspect;
    }
    let distance = planeHeight * 0.5 / Math.tan( camera.fov * 0.5 * (Math.PI/180) );
    let cameraDir = new THREE.Vector3();
    camera.getWorldDirection( cameraDir );
    planeMesh.position.set( camera.position.x, camera.position.y, camera.position.z );
    planeMesh.position.add( cameraDir.multiplyScalar( distance ) );
    planeMesh.rotation.setFromRotationMatrix( camera.matrix );
  }

pass in the plane mesh and the height of the plane mesh geometry when it was created.

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