- frustum(left, right, bottom, top, near, far, dst?): Mat4
#### Parameters

- left: number
The x coordinate of the left plane of the box.

- right: number
The x coordinate of the right plane of the box.

- bottom: number
The y coordinate of the bottom plane of the box.

- top: number
The y coordinate of the right plane of the box.

- near: number
The negative z coordinate of the near plane of the box.

- far: number
The negative z coordinate of the far plane of the box.

`Optional`

dst: Mat4Output matrix. If not passed a new one is created.

#### Returns Mat4

The perspective projection matrix.

- left: number

Computes a 4-by-4 perspective transformation matrix given the left, right, top, bottom, near and far clipping planes. The arguments define a frustum extending in the negative z direction. The arguments near and far are the distances to the near and far clipping planes. Note that near and far are not z coordinates, but rather they are distances along the negative z-axis. The matrix generated sends the viewing frustum to the unit box. We assume a unit box extending from -1 to 1 in the x and y dimensions and from 0 to 1 in the z dimension.