Fast Height-Field Rendering under Image-Based Lighting

We propose a new fast height-field rendering method for Image-Based Lighting. Our approach approximates the environmental illumination using spherical radial basis functions (SRBFs). We approximate the integrand of the rendering equation as a sum of products of the SRBFs and the visibility function. Then we solve the integral by approximating the visibility function of each SRBF as the fraction visible above the height-field. This fraction is precomputed into a 2-D texture, as a function of the SRBF size and its angle to the horizon. We use two different approximations of the horizon. The first, called a horizon map, can render more accurate self occlusion. The second, called a cone map, needs only a single RGBA 2D texture but can only render rough self-shadowing. Our approach can quickly render shading and self-shadowing of a height-field from all-frequency environmental lighting.