Qin, XueyingNakamae, EihachiroTadamura, KatsumiNagai, Yasuo2015-02-162015-02-1620031467-8659https://doi.org/10.1111/1467-8659.00671We propose a fast approach for photo-realistic rendering of trees under various kinds of daylight, which is particularlyuseful for the environmental assessment of landscapes. In our approach the 3D tree models are transformedto a quasi-3D tree database registering geometrical and shading information of tree surfaces, i.e. their normalvectors, relative depth, and shadowing of direct sunlight and skylight, by using a combination of 2D buffers.Thus the rendering speed of quasi-3D trees depends on their display sizes only, regardless of the complexity oftheir original 3D tree models. By utilizing a two-step shadowing algorithm, our proposed method can create highquality forest scenes illuminated by both sunlight and skylight at a low cost. It can generate both umbrae andpenumbrae on a tree cast by other trees and any other objects such as buildings or clouds. Transparency, specularreflection and inter-reflection of leaves, which influence the delicate shading effects of trees, can also be simulatedwith verisimilitude.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three dimensional Graphics and Realism10.1111/1467-8659.00671243-252