# 相机

## 全景相机

Cycles supports several types of panoramic cameras which are described in detail below. Note that these cannot be displayed in non-rendered modes in the viewport, i.e. Solid mode; they will only work for the final render.

### Equiangular Cubemap Face

Improves on Equirectangular by providing a more uniform distribution of rendered pixel of the spherical environment. This results in an image that has little variation in visual resolution for the entire spherical projection. This is in contrast to Equirectangular which can lose detail in the poles of the image. This is also in contrast to cube map projections which lose detail near the edges of each face.

This panorama type is great for virtual reality use cases where providing as much visual detail for a limited resolution is important.

A limitation over Equirectangular is that this method does not have longitude or latitude limits.

### 鱼眼透镜多项式

The projection works as follows. Pixels in the image are mapped to positions $$(x, y)$$ on the camera sensor in mm. A position on the sensor is mapped to a direction with spherical coordinates $$(1, \theta, \phi)$$ in radians as follows:

$\begin{split}& r = \sqrt{x^2 + y^2}\\ & \theta = k_0 + k_1 r + k_2 r^2 + k_3 r^3 + k_4 r^4\\ & \phi = acos(x/r)\end{split}$