Achieving camera zoom in threeJS without the use of trackball controls or any other camera control libraries

Currently, I'm utilizing threeJS to manipulate a camera within my scene. The camera is configured to orbit in a circular motion around an object when the left and right keys are pressed on the keyboard. However, I am seeking guidance on how to implement zoom functionality. Below is the snippet of my existing code:

camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 1, 10000 );
camera.position.set(0,20,35);
var rotSpeed = .02;

function checkRotation(){

    var x = camera.position.x,
        y = camera.position.y,
        z = camera.position.z;

    if (keyboard.pressed("left")){ 
        camera.position.x = x * Math.cos(rotSpeed) + z * Math.sin(rotSpeed);
        camera.position.z = z * Math.cos(rotSpeed) - x * Math.sin(rotSpeed);
    } else if (keyboard.pressed("right")){
        camera.position.x = x * Math.cos(rotSpeed) - z * Math.sin(rotSpeed);
        camera.position.z = z * Math.cos(rotSpeed) + x * Math.sin(rotSpeed);
    } else if(keyboard.pressed("up")){
        //zoom in
    } else if (keyboard.pressed("down")){
        //zoom out
    }

    camera.lookAt(scene.position);

}

Answer №1

To achieve a true zoom effect without physically moving the camera, adjust the field of view (fov) parameter of the camera with the following code snippet:

  camera.fov *= zoomFactor;
  camera.updateProjectionMatrix();

For a demonstration, refer to this example: http://jsfiddle.net/bvcCB/87/

If you prefer to move the camera closer or further from the target, calculate the vector between the camera position and the target, then move the camera along that calculated vector.

Answer №2

Starting from revision 69, a new feature allows you to utilize camera.zoom:

camera.zoom = zoomLevel;
camera.updateProjectionMatrix();

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