Research Of Glare Effect Simulation Based On Ray Tracing

Glare effect is a common physical phenomenon of nature, it will be more obvious when there is a powerful light source in the scene. Although glare effect will more or less have a negative effect in the process of imaging, it is of great importance to adding realism in the imaging simulation technology. Glare effect is often used in computer games, animation, post-production of film and other fields. When the light through imaging aperture or hits small particles on the propagation path, diffraction and scattering happens because of the wave-particle duality of light, inducing the phenomenon of uneven brightness on the imaging surface and it is called glare effect.Glare effect has a certain difference due to the different shapes of the imaging aperture or the particles hitting on the propagation path. But for the most situations, glare effect is mainly divided into two kinds:One is the divergent stripes around the light source, like a star effect, mainly caused by the diffraction phenomenon when the light through the imaging aperture; the other is the blurry halo surrounding the light source, known as the Bloom effect, mainly caused by the scattering phenomenon when the light hits small particles on the propagation path or dust and scratches on the surface of the lens and of the design defects of the lens. Therefore, this thesis mainly carried out the following work to simulate this glare effect:(1) Aiming at the star effect of the glare effect caused by the diffraction, this thesis uses the Huygens-Fresnel principle to calculate the light intensity distribution on the imaging plane after diffracting when the light through the imaging aperture. This thesis chooses Fraunhofer approximate to simplify the calculation of light intensity, then uses Fourier-Bessel function model to implement the actual model.(2) Aiming at the Bloom effect of the glare effect caused by the scattering, this thesis uses Gaussian convolution to implement. Powerful light source can increase the overall brightness around it, this thesis uses a two-dimensional Gaussian kernels to calculate with the highlight part of image, can not only simulate the Bloom effect, also smooth the image.(3) Due to the maturation of ray tracing technology and has lots of advantages in scene simulation compared to other algorithms, we introduce a method to accelerate calculation through the establishment of KD-tree spatial structure. This thesis will use the ray tracing algorithm frame to render the glare effect in the scene, and then get a relatively real glare picture, and outlook the implementation of real-time simulation in the future.