I was messing around trying to answer someone’s question about how to get a horizontal field of view, and I came up with this component. So, here you go! Hope it helps someone.
Edit: I modified the component to handle both perspective and orthographic cameras. Also, there are no more properties on the component. Simply attach to a camera, then use the camera’s properties as normal. Also, it now handles viewports, so it works with cameras that don’t occupy the entire screen.
There is one known issue. With an orthographic camera, if you attempt to adjust the viewport to be greater than the entire screen size, something internal to Unity resets the projection matrix and overrides this component’s behavior. To fix, simply toggle the component, or reload the scene or editor, anything that triggers the component to do its thing again.
using UnityEngine;
[ExecuteAlways]
[RequireComponent(typeof(Camera))]
public class HorizontallyAlignedCamera : MonoBehaviour
{
private Camera _camera;
private float _aspectRatio;
private float _fieldOfView;
private bool _isOrthographic;
private float _orthographicSize;
private void Awake()
{
_camera = GetComponent<Camera>();
}
private void OnEnable()
{
CachePropertiesAndRecalculate();
}
private void LateUpdate()
{
if(CameraPropertyHasChanged())
CachePropertiesAndRecalculate();
}
private void OnDisable()
{
_camera.ResetProjectionMatrix();
}
private bool CameraPropertyHasChanged()
{
bool hasChanged = (_aspectRatio != _camera.aspect
|| _fieldOfView != _camera.fieldOfView
|| _isOrthographic != _camera.orthographic
|| _orthographicSize != _camera.orthographicSize);
return hasChanged;
}
private void CacheCameraProperties()
{
_aspectRatio = _camera.aspect;
_fieldOfView = _camera.fieldOfView;
_isOrthographic = _camera.orthographic;
_orthographicSize = _camera.orthographicSize;
}
private void CachePropertiesAndRecalculate()
{
CacheCameraProperties();
if(_camera.orthographic)
RecalculateOrthographicMatrix();
else
RecalculatePerspectiveMatrix();
}
private void RecalculatePerspectiveMatrix()
{
float near = _camera.nearClipPlane;
float nearx2 = near * 2.0f;
float far = _camera.farClipPlane;
float halfFovRad = _camera.fieldOfView * 0.5f * Mathf.Deg2Rad;
// This is what aligns the camera horizontally.
float width = nearx2 * Mathf.Tan(halfFovRad);
float height = width / _camera.aspect;
// This is the default behavior.
//float height = nearx2 * Mathf.Tan(halfFovRad);
//float width = height * _camera.aspect;
float a = nearx2 / width;
float b = nearx2 / height;
float c = -(far + near) / (far - near);
float d = -(nearx2 * far) / (far - near);
Matrix4x4 newProjectionMatrix = new Matrix4x4(
new Vector4(a, 0.0f, 0.0f, 0.0f),
new Vector4(0.0f, b, 0.0f, 0.0f),
new Vector4(0.0f, 0.0f, c, -1.0f),
new Vector4(0.0f, 0.0f, d, 0.0f));
_camera.projectionMatrix = newProjectionMatrix;
}
private void RecalculateOrthographicMatrix()
{
// This is what aligns the camera horizontally.
float width = 2.0f * _camera.orthographicSize;
float height = width / _camera.aspect;
// This is the default behavior.
//float height = 2.0f * _camera.orthographicSize;
//float width = height * _camera.aspect;
float near = _camera.nearClipPlane;
float far = _camera.farClipPlane;
float a = 2.0f / width;
float b = 2.0f / height;
float c = -2.0f / (far - near);
float d = -(far + near) / (far - near);
Matrix4x4 newProjectionMatrix = new Matrix4x4(
new Vector4(a, 0.0f, 0.0f, 0.0f),
new Vector4(0.0f, b, 0.0f, 0.0f),
new Vector4(0.0f, 0.0f, c, 0.0f),
new Vector4(0.0f, 0.0f, d, 1.0f));
_camera.projectionMatrix = newProjectionMatrix;
}
}
