Understanding Intensity Distribution
According to the intensity distribution, the Integration Angle will play a role or not. This page is dedicated to help you understand which distribution is impacted by the Integration Angle.
General Description
As described in the Overview, the Integration Angle has been introduced in case of a Direct Simulation to provide results in a system with specular contributions.
To be accurate, the Integration Angle has no impact when a continuous/diffuse distribution is used (IES/Eulumdat/xmp for a source or a BSDF for a surface). Indeed, Speos does not need to find an approximation thanks to the solid angle as it uses the distribution to obtain the exact value in the requested direction. A diffuse distribution generates rays in several random directions with a drawing density proportional to the value of the distribution, whereas a specular contribution generates only one ray.
When the rays are generated with a Dirac distribution, after specular interaction, or when the rays come from a ray file, Speos needs to make a density estimation to force/help these rays to find the sensors. As a consequence, the Integration Angle will be useful to solve this issue.
Ray File Case
A ray file is a file that stores information regarding the position, direction and wavelength of several rays that have been measured from a light source.
Let's take the example of *.ies and *.eulumdat distribution files. From Speos, a ray file can be created out of a *.ies or *.eulumdat distribution file. Speos will randomly sample the *.ies or *.eulumdat file and store all the resulting individual rays in the ray file. Each ray stored is considered as a single Dirac (with only one direction). Therefore, a ray file is a collection of Diracs and the continuous distribution nature of the *.ies or *.eulumdat file no longer exists.
As a consequence, a Ray File Source used in a Direct Simulation will benefit from the Integration Angle for its rays to find the sensor.