Users can now better mimic real-world cameras by specifying the focal length of

the virtual camera in 3D plots. An increasing focal length between 1 and

+infinity "flattens" the image, while a decreasing focal length between 1 and 0

infinity "flattens" the image, while a decreasing focal length between 1 and 0

exaggerates the perspective and gives the image more apparent depth. The

default focal length of 1 corresponds to a Field of View (FOV) of 90 deg, and

is backwards-compatible with existing 3D plots.

The focal length can be calculated from a desired FOV via the equation:

..mathmpl::

focal\_length = 1/tan(FOV/2)

..plot::

:include-source: true

frommpl_toolkits.mplot3dimportaxes3d

axs[0].set_proj_type('ortho')# FOV = 0 deg

axs[0].set_title("'ortho'\nfocal_length =+∞",fontsize=10)

axs[0].set_title("'ortho'\nfocal_length = ∞",fontsize=10)

axs[1].set_proj_type('persp')# FOV = 90 deg

_api.check_in_list(['persp','ortho'],proj_type=proj_type)

ifproj_type=='persp':

iffocal_lengthisNone:

self.focal_length=1

else:

iffocal_length<=0:

raiseValueError(f"focal_length ={focal_length} must be"+

raiseValueError(f"focal_length ={focal_length} must be"

" greater than 0")

self.focal_length=focal_length

elifproj_type=='ortho':

iffocal_lengthnotin (None,np.inf):

raiseValueError(f"focal_length ={focal_length} must be"+

raiseValueError(f"focal_length ={focal_length} must be"

f"None for proj_type ={proj_type}")

self.focal_length=np.inf

else:

raiseValueError(f"proj_type ={proj_type} must be in"+

f"{'persp','ortho'}")

def_roll_to_vertical(self,arr):