Study of Visual Simulation of Snow and Ice Phenomena

本研究旨在开发一种技术来实现对冬季景观的真实模拟。为此，我们开发了以下方法：(1)积雪表面几何变形方法：一种以积雪硬度为参数实现积雪表面几何变形的方法。使用这种方法，可以根据雪的质量进行几何变形。(2)雪面图案表达方法：一种自动生成雪面图案的方法。对于雪槽和雪窝，通过对积雪表面进行设置操作生成图案。对于浮纹、横纹和波纹，采用细胞自动机和粒子模拟相结合的方法自动生成图案。利用该方法，可以实现积雪表面从条状到波纹状再到细纹状的连续变化。(3)雪/冰增生的表达方法：一种能够自动生成雪花和冰粒在物质上增生形成图案的方法。将该方法应用于树木的形状，生成了软时间的图案。(4)表示雪的快速渲染方法：一种能够渲染由粒子定义的雪的方法。使用Z-buffer方法和纹理映射可以实现快速渲染。(5)冰柱快速生成法：一种能够程序化自动生成冰柱样图案的方法。

This study aims to develop a technique that would realize a realistic simulation of a winter landscape. For this purpose, we developed the following methods:(1) Geometry distortion method of snow cover surface:A method to enable geometry distortion of a snow cover surface with the hardness of snow as a parameter. With this method, geometry distortion can be done according to the quality of snow.(2) Expression method of snow surface pattern:A method to enable automatic generation of snow surface patterns. As to snow penitents and snow dimples, a pattern is generated by performing a set operation for a snow cover surface. As to skavlers, barchans and ripples, a pattern is automatically generated with a method where simulations of cellular automata and particles are combined. With this method, the pattern of snow cover surface can be consecutively changed from barchan to ripple to skavler.(3) Expression method of snow accretion/ice accretion:A method to enable automatic generation of the pattern formed by the accretion of snowflakes and ice particles on substances. By applying this method for the shape of trees, patterns of soft rime are generated.(4) Fast-rendering method for expressing snow:A method to enable rendering the snow defined by particles. Fast rendering is possible with the use of the Z-buffer method and texture mapping.(5) Fast generation method of icicle:A method to enable automatic generation of icicle-like patterns in a procedural manner.