Real-time Global Illumination For Dynamic Light Sources Based On Light-G-Buffer

In recent years,probe-based global illumination algorithms are widely used in real-time rendering applications,such as virtual reality,games,and CAD-aided design,due to their sim-plicity and efficiency.To generate global illumination effects,the basic idea of this kind of algorithms is firstly placing discrete probes in the scenes and precomputing the lighting infor-mation,and then interpolating the lighting information stored in several probes near the shading point on the fly.However,this kind of algorithms relies on precomputing lighting information for each probe,which makes it difficult to respond to dynamic illumination in real time.Among them,the light field probe method can generate high-quality indirect diffuse and glossy reflection effect,but it needs to precompute much more information for each probe,including scene geometry,radiance and irradiance information.In this paper,we take the light field probe method as research object,and analyze its prob-lems of coupling geometric and lighting information stored in the probes and the redundancy of lighting information of adjacent probes.To address these problems,we propose a real-time global illumination algorithm for dynamic light sources based on Light-G-Buffer.In order to handle dynamic light sources,the basic idea of our algorithm is to decouple the handling of geo-metric and lighting information in the light field probes,not to generate radiance and irradiance information in the precomputation stage,but to reconstruct them on the fly.Specifically,the main contributions of this paper are as follows:·First,this paper proposes a new data structure called Light-G-Buffer to represent indirect lighting information.The Light-G-Buffer generated at runtime stores material informa-tion and radial distance information from the light source,which is more compact and efficient than the radiance field stored in the probes,and can accurately represent the one-bounce lighting information.The Light-G-Buffer structure can be efficiently updated on the fly to respond to dynamic illumination by rasterization and multiple rendering target techniques.·Second,this paper reconstructs the radiance field and irradiance field of the probes in real time based on the runtime Light-G-Buffer and the precomputed geometric probes.On the one hand,combining these two information,this paper can calculate the incident radiance in any direction based on the deferred shading method,so as to reconstruct the radiance field;on the other hand,based on the reconstructed radiance field,this paper proposes a parallel spherical harmonic projection algorithm to significantly accelerate the convolution of irradiance maps,so as to reconstruct the irradiance field.Based on the reconstructed radiance field and irradiance field,our algorithm can accurately generate the global illumination effects of one-bounce diffuse and glossy reflection under dynamic illumination.·Finally,the multi-bounce diffuse lighting effect and the multi-light scene are supported under the premise of allowing a certain rendering error.On the one hand,by assum-ing that the scene’s material is ideal diffuse,this paper derives a formula for calculating the incident radiance of the probes after multiple bounces and uses a frame-by-frame calculation strategy to generate multi-bounce diffuse lighting effect in real time;on the other hand,for multi-light scenes,this paper proposes a light clustering method based on greedy strategy,which clusters light sources based on constraints such as mutual distance and visibility of light sources,thus significantly reducing the number of Light-G-Buffer and improving the runtime efficiency.The experimental results show that the Light-G-Buffer structure has significant advantages over the light field probe method in terms of storage,update and query;Based on Light-G-Buffer,our algorithm can reconstruct the radiance and irradiance field of the light field probes in real time with high efficiency and low error,and generate real-time global illumination effects with multiple diffuse and glossy reflections under dynamic illumination;The light clustering algorithm proposed in this paper can significantly reduce the overhead of generating Light-G-Buffer and improve the runtime efficiency in multi-light scenarios.