# 相机

## 全景相机

Cycles支持三种类型的全景相机类型：等距圆柱（ERP）、鱼眼和镜像球。请注意，这些全景效果不能在非渲染模式下呈现于视图中，即 实体 模式；它们只会在最终渲染的时候生效。

### 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:

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