• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.398-407
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• 2012

We propose a tree modeling method of expressing realistically and efficiently numerous trees distributed on a broad terrain. This method combines and simplifies the recursive hierarchy of tree branch and branch generation process through self-organizing from buds, allowing users to generate trees that can be used more intuitively and efficiently. With the generation process the leveled structure and the appearance such as branch length, distribution and direction can be controlled interactively by user. In addition, we introduce an environment-adaptive model that allows to grow a number of trees variously by controlling at the same time and we propose an efficient application method of growing environment. For the real-time rendering of the complex tree models distributed on a broad terrain, the rendering process, the LOD(level of detail) for the branch surfaces, and shader instancing are introduced through the GPU(Graphics Processing Unit). Whether the numerous trees are expressed realistically and efficiently on wide terrain by proposed models are confirmed through simulation.

• Journal of the Korea Computer Graphics Society
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• v.23 no.5
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• pp.29-38
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• 2017

We propose a method for tree-inspired chair modeling that can generate a tree-branch pattern in the skeleton of an arbitrary chair shape. Unlike existing methods that merge multiple-input models, the proposed method requires only one mesh as input, namely the contour mesh of the user's desired part, to model the chair with a branch pattern generated by tree-growth simulation. We propose a new method for the efficient extraction of the contour-mesh region in the tree-branch pattern. First, we extract the contour mesh based on the face area of the input mesh. We then use the front and back mesh information to generate a skeleton mesh that reconstructs the connection information. In addition, to obtain the tree-branch pattern matching the shape of the input model, we propose a three-way tree-growth simulation method that considers the tangent vector of the shape surface. The proposed method reveals a new type of furniture modeling by using an existing furniture model and simple parameter values to model tree branches shaped appropriately for the input model skeleton. Our experiments demonstrate the performance and effectiveness of the proposed method.

• Journal of Korea Multimedia Society
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• v.16 no.5
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• pp.637-646
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• 2013

In order to model a variety of natural trees that are appropriate to outdoor terrains consisting of multiple trees, this study proposes a modeling method of new growth rules(based on the convolution sums of divisor functions). Basically, this method uses an existing growth-volume based algorithm for efficient management of the branches and leaves that constitute a tree, as well as natural propagation of branches. The main features of this paper is to introduce the theory of convolution sums of divisor functions that is naturally expressed the growth or fate of branches and leaves at each growth step. Based on this, a method of modeling various tree is proposed to minimize user control through a number of divisor functions having generalized generation functions and modification of the growth rule. This modeling method is characterized by its consideration of both branches and leaves as well as its advantage of having a greater effect on the construction of an outdoor terrain composed of multiple trees. Natural and varied tree model creation through the proposed method was conducted, and using this, the possibility of constructing a wide nature terrain and the efficiency of the process for configuring multiple trees were evaluated experimentally.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.426-429
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• 2011

광범위한 지형을 배경으로 하는 게임과 같은 실시간 시뮬레이션 시스템에서 사실적 표현을 높이는 중요한 요소 중 하나가 나무와 같은 자연물 표현이다. 하지만 시스템에 적합한 나무 모델을 매번 새롭게 제작하고 표현하는 일은 다소 어려움이 따른다. 본 연구는 이러한 문제를 해결하기 위하여 실시간 시스템에 적합한 다양하고 사실적인 나무를 모델링하는 방법을 설계한다. 이는 프랙탈 기반의 재귀적 계층 구조를 바탕으로 가지 성장의 자기조직화 처리를 결합하여 나무 성장 과정을 단순화시킴으로써 실시간 시스템에서 직관적이고 효율적으로 활용가능하게 한다. 또한 다양한 나무 모델을 자연스럽게 생성할 수 있도록 인터렉티브 제어 요소를 정의함은 물론 실시간 시스템 내 많은 수의 복잡한 나무 모델을 효율적으로 렌더링하기 위한 GPU를 기반으로 한 가지 표면에 대한 LOD 설정과 인스턴싱 방법을 추가하여 그 결과를 함께 보인다.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2000.11a
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• pp.341-348
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• 2000

의사결정 나무라고 불리우기도 하는 나무모형은 결과 해석의 용이성으로 데이터마이닝의 분류예측 모형으로써 큰 각광을 받고 있다. 현재 나무모형으로 가장 많이 사용되는 Breiman et. al의 CART나 Quinlan의 C4.5 모두 생성된 노드들의 자료 구성이 목표변수를 기준으로 수준 구성비 측면에서 순수해지도록 진행된다. 그러나 CRM에 있어 가장 흔한 주제인 해지예측을 위한 모델링을 실시하는 경우 관심의 대상인 해지자가 전체 자료에 극히 일부를 차지하여, 기존의 분할 방법에서와 같이 모든 노드의 순수성을 고려하기란 불가능하다. Buja와 Lee는 이와 같이 소수의 관심에 대상이 되는 부류를 찾아내기 위한 나무모형 생성방법을 소개하였다 즉, 해지자 관리가 중요한 경우 해지자와 비해지자 구분을 진행하는 기존의 방법과는 달리 전체 자료 중 해지자를 집중적으로 찾아가는 탐색적 분할 기준인 단측 순수성(one-sided purity)을 제안하였다. 본 연구에서는 단측 순수성에 의한 나무모델링을 모 PC통신 회사의 해지자 자료에 적용하며 기존의 방법과 비교하였고 몇 가지 시뮬레이션 자료를 통해 단측 순수성의 문제점과 앞으로 해결하여야 할 과제에 대하여 살펴보았다.

• Journal of Intelligence and Information Systems
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• v.7 no.1
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• pp.17-25
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• 2001

Tree model is the most popular classification algorithm in data mining due to easy interpretation of the result. In CART(Breiman et al., 1984) and C4.5(Quinlan, 1993) which are representative of tree algorithms, the split fur classification proceeds to attain the homogeneous terminal nodes with respect to the composition of levels in target variable. But, fur instance, in the chum prediction modeling fur CRM(Customer Relationship management), the rate of churn is generally very low although we are interested in mining the churners. Thus it is difficult to get accurate prediction modes using tree model based on the traditional split rule, such as mini or deviance. Buja and Lee(1999) introduced a new split rule, one-sided purity for classifying minor interesting group. In this paper, we compared one-sided purity with traditional split rule, deviance analyzing churning vs. non-churning data of ISP company. Also reviewing the result of tree model based on one-sided purity with some simulated data, we discussed problems and researchable topics.