Image Synthesis for Visual Simulation of Natural Scenery

(1)地形建模：我们首先将Musgrave提出的erosin算法应用到我们的脊线递归细化方法生成的数字地形模型中，使山形更加自然，我们已经证明，我们可以获得与原始形状不同的视觉印象的山形，例如风化造成的平缓弯曲的山形和侵蚀陡峭的山形。接下来，我们对侵蚀模型进行了详细的研究，明确了侵蚀模型的机制不同于自然侵蚀现象。因此，建立基于自然侵蚀现象的侵蚀模型仍然是一个具有挑战性的问题。(2)季节性山地模拟：已开发出针对给定山型生成适当植被的技术。这种方法既适用于真实的山，也适用于想象中的山。此外，还开发了用于绘制森林的简单图像生成算法。(3)森林纹理：我们开发了直接从树木生长算法生成的树木几何模型中生成森林三维纹理的技术。因此，可以很容易地生成两种或两种以上树木共存的复杂森林纹理。(4)降雪和积雪的模拟：建立了一个在体素空间中工作的雪粒子行为模型。利用该模型可以模拟典型类型的积雪，如冠积雪。基于涡场法技术，提出了一种降雪模拟方法。因此，在包括建筑物、树木和花园石头在内的小规模景观中模拟积雪和降雪成为可能。

(1) Terrain modeling : We first applied the erosin algorithm proposed by Musgrave to the digital terrain models generated by our recursive refinement method for ridge-lines in order to make the moutain shapes more natural, and we have shown that we can obtain the mountain shapes having visual impressions different from those of the original shapes, such as mountains having gentle curved surfaces caused by weathering and eroded steep mountains. Next, we investigated the erosion model in detail and have clarified that the mechanism of the erosion model was different from that of a natural erosin phenomenon. Therefore, development of an erosin model based on the erosin phenomenon of nature still remains a challenging problem.(2) Simulation of seasonal mountains : The technique for generating appropriate vegetation for a given mountain shape has been developed. This techinique is applicable to both an real mountain and an imaginary mountain. Moreover, simple image generation algorithm for rendering forests has been developed.(3) Texture of a forest : We have developed the technique for producing three dimensional texture of the forest directly from the geometric model of a tree generated by a growth algorithm of trees. As a result, a complex forest-texture where two or more kinds of trees exist together can be generated easily.(4) Simulation of snowfall and snow cover : A behavioral model of a snow particle which works in voxel space has been developed. The typical type of snow cover such as crown snow can be simulated by using this model. The snowfall simulation method has been developed based on the technique of a vortex field method. Thus, simulation of snow cover and snowfall in a small-scale scenery such as a close-range view including buildings, trees, and garden stones has became possible.