# Functions to calculate the visible width / height at a given z-depth from a perspective camera

**URL:** <https://discourse.threejs.org/t/functions-to-calculate-the-visible-width-height-at-a-given-z-depth-from-a-perspective-camera/269>\
**Category:** Resources\
**Tags:** perspective-camera, camera\
**Created:** [April 28, 2017, 10:02am UTC](https://discourse.threejs.org/t/functions-to-calculate-the-visible-width-height-at-a-given-z-depth-from-a-perspective-camera/269 "2017-04-28T10:02:14Z")\
**Posts on this page:** 1\
**Showing post:** 1

<div class="post-metadata">

**Author:** ![looeee](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.threejs.org/looeee/32/59_2.png) [@looeee](https://discourse.threejs.org/u/looeee)\
**Post date:** [April 28, 2017, 10:02am UTC](https://discourse.threejs.org/t/functions-to-calculate-the-visible-width-height-at-a-given-z-depth-from-a-perspective-camera/269/1 "2017-04-28T10:02:14Z")

</div>

These two functions will give you the visible height and width in your scene at a given distance from a PerspectiveCamera.

It’s useful if you want to create an object that is the full width / height of the scene, or want to place objects at screen edges etc.

Here’s the code (ES6):

```auto
const visibleHeightAtZDepth = ( depth, camera ) => {
  // compensate for cameras not positioned at z=0
  const cameraOffset = camera.position.z;
  if ( depth < cameraOffset ) depth -= cameraOffset;
  else depth += cameraOffset;

  // vertical fov in radians
  const vFOV = camera.fov * Math.PI / 180; 

  // Math.abs to ensure the result is always positive
  return 2 * Math.tan( vFOV / 2 ) * Math.abs( depth );
};

const visibleWidthAtZDepth = ( depth, camera ) => {
  const height = visibleHeightAtZDepth( depth, camera );
  return height * camera.aspect;
};

```

There are quite a few examples of this function around the web, but I haven’t seen any that compensate for camera positioning.

Note that I’ve only tested this when the camera is facing in the default direction (i.e. along the negative z-axis) and the depth considered is further along the axis, although I think it will work in other directions as well.

---

_[View the full topic](https://discourse.threejs.org/t/functions-to-calculate-the-visible-width-height-at-a-given-z-depth-from-a-perspective-camera/269)._