All-Frequency Direct Illumination with Vectorized Visibility

Many existing pre-computed radiance transfer (PRT) approaches for all-frequency lighting store the information of a 3D object in the pre-vertex manner. To preserve the fidelity of high frequency effects, the 3D object must be tessellated densely. Otherwise, rendering artifacts due to interpolation may appear. This paper presents an all-frequency lighting algorithm for direct illumination based on a new visibility representation which approximates a visibility function using a sequence of 3D vectors. The algorithm is able to construct the visibility function of an on-screen pixel on-the-fly. Hence even though the 3D object is not tessellated densely, the rendering artifacts can be suppressed greatly. Besides, a summed area table based rendering algorithm, which is able to handle the integration over a non-axis aligned polygon, is developed. Using our approach, we can rotate lighting environment, change view point, and adjust the shininess of the 3D object in a real-time manner. Experimental results show that our approach can render plausible all-frequency lighting effects for direct illumination in real-time, especially for specular shadows, which are difficult for other methods to obtain.