Image Synthesis for Visual Simulation of Natural Scenery

(1)地形建模：为了使山体形状更加自然，我们首先将Musgrave提出的侵蚀算法应用到我们的山脊线递归精化方法生成的数字地形模型中，并证明我们可以获得具有不同于原始形状的视觉印象的山体形状，例如具有由风化引起的平缓曲面的山体和被侵蚀的陡峭山体。其次，我们详细研究了侵蚀模型，并阐明了侵蚀模型的机制不同于自然侵蚀现象。因此，基于自然界的侵蚀现象建立侵蚀模型仍然是一个具有挑战性的问题。(2)模拟季节性山脉：已开发出为特定山脉形状生成适当植被的技术。这种技术既适用于真实的山，也适用于想象中的山。此外，简单的图像生成算法绘制森林已经开发。(3)森林的纹理：我们已经开发出的技术，直接从树木的生长算法生成的树木的几何模型产生的三维纹理的森林。因此，可以很容易地生成两种或多种树木共存的复杂森林纹理。(4)降雪和积雪的模拟：已经开发了一个在体素空间中工作的雪粒子的行为模型。利用该模型可以模拟冠状雪等典型积雪类型。基于涡场方法的技术，发展了降雪模拟方法。因此，在包括建筑物、树木和花园石头的小尺度场景中模拟积雪和降雪已经成为可能。

(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.