Reflection, scattering?

The reflection of a light passing through a smooth surface is called a mirror reflection. The mirror reflection follows the law of reflection. The reflected light is regular, that is, a high light, which forms a specific area. the reflection of Flat mirrors, spherical mirrors, and various curved surfaces is mirror reflection. mirror reflection can generate various images, and can be observed in proper positions and ranges. in reality, a large amount of reflection is not carried out on a smooth surface, and the reflective surface is rough. irregular reflection on a rough surface is called diffuse reflection. after the light is reflected by a rough surface, the diffuse reflection may be in all directions, but each of the rays follows the law of reflection. A general object is the result of diffuse reflection.
Scattering: it is because of the presence of tiny particles (heterogeneous bodies) in the media or the action of molecules on the light, so that the beam deviates from the original propagation direction and spreads around.
When the solar radiation passes through the atmosphere and encounters air molecules, dust particles, cloud drops, and other quality points, scattering occurs. However, scattering does not convert radiant energy into heat energy as absorption, but only changes the radiation direction, so that the solar radiation spreads in all directions with the focus of the particle. After scattering, some of the solar radiation cannot reach the ground. If the solar radiation encounters an air molecule with a smaller diameter than the wavelength, the shorter the wavelength of the radiation, the more scattered it is. The relationship between the scattering capability and wavelength is as follows: for molecules of a certain size, the scattering capability is inversely proportional to the four quadrants of the wavelength, which is selective. For example, when the wavelength is 0.7 microns, the scattering capacity is 1, and when the wavelength is 0.3 microns, the scattering capacity is 30. Therefore, when solar radiation passes through the atmosphere, light with a shorter wavelength is scattered much due to air molecular scattering. After the rain, the sky is blue, because the blue wavelength in the radiation is short, it is easy to be scattered by the atmosphere. If the sun radiation encounters a particle with a larger diameter than a wave, although it is also scattered, this scattering is not selective, that is, the various wavelengths of the radiation are also scattered. If there are many dust or fog particles in the air, the long and short waves in a certain range are also scattered, making the sky gray. Sometimes, to distinguish selective scattering from non-selective scattering, the former is called scattering, and the latter is called diffuse.
For the substances with selective scattering, BRDF is called anisotropic BRDF. Otherwise, it is isotropic BRDF.