Creating a camera in code typically looks like this:
var camera = new THREE.PerspectiveCamera(
FOV,
ASPECT_RATIO,
NEAR_PLANE,
FAR_PLANE
);
But what exactly do these values represent?
Creating a camera in code typically looks like this:
var camera = new THREE.PerspectiveCamera(
FOV,
ASPECT_RATIO,
NEAR_PLANE,
FAR_PLANE
);
But what exactly do these values represent?
I had the same question, so I decided to do some research and found out that it is called a "frustum".
Here's a code comment from a recent project that explains it quite well in my opinion.
// Curious about what a frustum is? I was too.
// Imagine it as a pyramid with the top cut off. The peak represents the camera.
// Anything within the pyramid starting from the "near plane" is visible on screen.
// Once you pass the "far plane" (the base of the pyramid), objects are too far to be seen.
// Anything outside the pyramid is off-screen. Consider also the "aspect ratio" (the base's rectangle)
// and the "field of view" (similar to a lens, distorting the pyramid for more objects on screen - measured in degrees,
// with 45° as a "natural" perspective. A higher number means more "perspective" in the view).
Understanding FOV (field of view) is like envisioning a camera on a tripod; when you switch to a wide-angle lens, the FOV increases. Picture a cone extending from the camera, only able to capture objects within its range.
Aspect ratio refers to the proportion of width to height, such as 16/9 for widescreen TVs and 4/3 for older models. When working with three.js, provide either the screen dimensions or the DIV size you want to use for your project.
I came across this tutorial that was incredibly helpful in grasping all the camera parameters and the distinctions between PerspectiveCamera and OrthographicCamera.
PerspectiveCamera
Fov (Field of view) - This determines the visible area from the camera's position. Typically, humans have nearly 180-degree field of view, while some birds have a full 360-degree field of view. Computers usually use a field of view between 60 and 90 degrees.
Aspect - The aspect ratio represents the ratio between the horizontal and vertical size of the rendering area. It usually matches the window size ratio, with the common value being
window.innerWidth / window.innerHeightNear - This sets the minimum distance from the camera that Three.js will render the scene. Typically a small value like 0.1.
Far - This specifies the maximum distance at which the scene is visible from the camera. It's crucial for balancing rendering performance, with a normal range between 500 and 2000.
OrthographicCamera
Left (Camera frustum left plane) - Indicates the leftmost border of the rendered scene.
Right (Camera frustum right plane) - Denotes the rightmost border of the rendered area.
Top (Camera frustum top plane) - Marks the maximum top position in the renderable area.
Bottom (Camera frustum bottom plane) - Specifies the bottom position in the renderable area.
Near (Camera frustum near plane) - From this point onwards, the scene gets rendered based on the camera's position.
Far (Camera frustum far plane) - Represents the maximum distance from the camera where the scene gets rendered.
The image below serves for better understanding:
https://i.sstatic.net/3hUZ2.png
The key contrast between the two camera types is in OrthographicCamera, where distance does not impact the size of elements, as demonstrated by the red and yellow balls.
Here's a code snippet to switch between the two camera types:
this.switchCamera = function(SCENE_WIDTH, SCENE_HEIGHT) {
if (camera instanceof THREE.PerspectiveCamera) {
camera = new THREE.OrthographicCamera( SCENE_WIDTH / - 2, SCENE_WIDTH / 2, SCENE_HEIGHT / 2, SCENE_HEIGHT / - 2, 0.1, 1000 );
camera.position.x = 0;
camera.position.y = 0;
camera.position.z = -1;
camera.lookAt(scene.position);
this.perspective = "Orthographic";
} else {
camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 0.1, 1000 );
camera.position.x = 0;
camera.position.y = 0;
camera.position.z = -1;
camera.lookAt(scene.position);
this.perspective = "Perspective";
}
};
Notes:
camera.lookAt(scene.position) aligns the camera with the scene for visibility.three.js are in SI units, so left,right,top,bottom values are not pixels.SCENE_WIDTH, SCENE_HEIGHT can be obtained from the scene geometries. An orthographic frustum larger than the scene is not very efficient. Useful links:
Field of view (FOV) refers to the vertical angle of the camera frustum.
Aspect ratio is the ratio of the width to the height of the camera frustum.
The near plane of the camera frustum is the closest plane to the camera.
The far plane of the camera frustum is the farthest plane from the camera.
Discover images illustrating the FOV, near plane, and far plane on the following pages:
For more information on cameras in Three.js, visit the following links:
https://en.wikipedia.org/wiki/Viewing_frustum
Learn about aspect ratio in images at:
https://en.wikipedia.org/wiki/Aspect_ratio_(image)
Refer to the official documentation for PerspectiveCamera in Three.js at:
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