Integrators

The integrator is the element that implements the rendering operation, i.e. the forward simulation of the TVAM process. It start light paths on the projector, and computes their propagation in the scene until they reach the sensor, and it then accumulates absoption on the sensor’s film.

Volume integrator (volume)

The main integrator that should be used to model the TVAM process and for optimization is the volume integrator. It is a custom integrator that is specifically designed to compute the absorption map in the volumetric film.

It can be loaded as a Mitsuba plugin:

integrator = mi.load_dict({
    'type': 'volumeintegrator',
    'print_time': 20.0,
})

It takes the following parameters:

Key	Type	Description
sample_time	bool	Flag that specifies if the time dimension should be sampled stochastically or not. If True, the integrator will generate samples from each projector pixel at random angles, which allows to account for motion blur. Otherwise, each path will start at the discrete angles determined by the number of patterns in one rotation. Defaults to False.
regular_sampling	bool	Whether light paths should start from the center of each projector pixel or not. By default, paths start from a random position within one pixel. Defaults to False.
print_time	float	Total printing time, in seconds. This defines the total exposure time. Defaults to 1.0.
target_id	str	The ID of the target shape for an optimization. This is useful in certain cases where it is necessary during the rendering phase to know if the shape that a light path is interacting with is the target or not. Defaults to ‘target’.
transmission_only	bool	Flag that specifies if the integrator should only evaluate the transmission component of the BSDF at each interaction. This allows to force all paths to enter the medium while still correctly accounting for attenuation at the interfaces. Defaults to True.

Radon integrator (radon)

For convenience, we also provide an integrator that computes the Radon transform of the target object. It accepts the same parameters as the volume integrator.

Warning

This integrator is a forward-only integrator, and cannot be used for optimization. It is only useful to compute the Radon transform of a shape.