Allow setting the camera "field of view"

It doesn't seem possible to set the 3D camera field of view (fov).

(Re: my post to Stackoverflow.)

Looking at the source code, I see that:

In https://github.com/plotly/plotly.js/blob/master/src/plots/gl3d/scene.js, it uses glPlot3d.createScene and sets the options in proto.prepareOptions.

In https://github.com/gl-vis/gl-plot3d/blob/master/scene.js#L179, the allowed options include the field-of-view parameter fovy (field-of-view in the vertical direction), which defaults to Math.PI/4 (45 degrees).

For 3D graphics, a 45-degree vertical field-of-view typically gives an exaggerated perspective. It corresponds to about a 28mm camera lens.

It would be nice for plotly.graph_objects.layout.scene.Camera to include a fovy parameter (in radians).

从 plotly.py 的 layout.scene.Camera 定义开始，追踪相机选项如何传递到 plotly.js。阅读 src/plots/gl3d/scene.js，尤其是 proto.prepareOptions，并将其选项与 gl-plot3d 的 scene.js 约第 179 行附近的选项进行比较。当 Python 相机 API 接受以弧度表示的 fovy，并将其传递到 3D 场景时，即视为完成。