Study of Visual Simulation of Snow and Ice Phenomena

本研究的目的是开发一种技术，将实现一个逼真的模拟冬季景观。（1）积雪面几何变形方法：以积雪硬度为参数，实现积雪面几何变形的方法。该方法可以根据雪的质量进行几何变形。(2)雪面图案的表示方法：能够自动生成雪面图案的方法。对于雪坑和雪坑，通过对积雪表面执行设置操作来生成图案。对于Skavlers、barchans和ripples，采用元胞自动机和粒子模拟相结合的方法自动生成图案。该方法可实现积雪表面形态从新月形到涟漪形再到锯齿形的连续变化。(3)积雪/积冰的表示方法：能够自动生成由雪花和冰粒在物质上的积冰形成的图案的方法。通过将该方法应用于树木的形状，生成了软雾凇的图案。(4)表示雪的快速渲染方法：一种启用渲染由粒子定义的雪的方法。使用Z缓冲区方法和纹理映射可以快速渲染。(5)冰柱快速生成方法：一种能够以程序化方式自动生成冰柱状图案的方法。

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.