基于Opengl的屏幕对象拾取 毕业论文

论文题目： 基于OpenGL的屏幕对象拾取 系 别： 计算机系 专业年级：

学 号： 姓 名： 指导教师、职称：

年 05 月 10 日

I

目录

摘要 ................................................................................ 1 ABSTRACT ............................................................................ 2 1 绪论 .............................................................................. 3 1.1 课题的目的和意义 ................................................................ 3 11..22 拾拾取取技技术术国国内内外外研研究究 .............................................................. 3 1.3 本论文研究主要内容 .............................................................. 3 2 基于OPENGL＋MFC的建模基础 ........................................................ 5 2.1 OpenGL概括 ...................................................................... 5 2.2 OpenGL渲染管线过程 .............................................................. 5 2.2.1顶点变换 ..................................................................... 6 2.2.2图元组装 ..................................................................... 6 2.2.3图元处理 ..................................................................... 6 2.2.4片元处理 ..................................................................... 6 2.2.5光栅化操作 ................................................................... 6 2.3 MFC概述 ......................................................................... 6 2.4 MFC特点 ......................................................................... 7 2.4.1封装 ......................................................................... 7 2.4.2继承 ......................................................................... 8 2.4.3虚拟函数和动态约束 ........................................................... 8 2.5 应用程序的构成 .................................................................. 8 2.6 基于OpenGL+MFC的三维模拟的编程环境配置 ......................................... 9 3 拾取技术 ......................................................................... 12 3.1 基于射线求交拾取技术 ........................................................... 12 3.1.1判断线段和包围盒的相对位置 .................................................. 12 3.2 基于GPU的重绘式拾取技术 ....................................................... 14 3.3 各种拾取技术比较 ............................................................... 16 4 系统的设计及实现 ................................................................. 18 4.1 系统的选择机制 ................................................................. 18 4.1.1进入选择模式之前 ............................................................ 18 4.1.2获取当前选择模式 ............................................................ 18 4.1.3退出选择模式 ................................................................ 20 4.1.4拾取 ........................................................................ 20 4.2 拾取结果截图 ................................................................... 21 5 结论与展望 ...................................................................... 25 5.1 结论 ........................................................................... 25 5.2 展望 ........................................................................... 25 参考文献 ........................................................................... 26 致谢 ............................................................................... 28

II

摘要

屏幕对象的拾取是计算机图形处理系统中一个重要的功能，在许多情况下，计算机图形处理系统不仅要绘制图形，而且要允许操作者能够通过输入设备(通常是鼠标)操纵屏幕上的物体(标识、移动和修改)。有时还需要获取物体上点的空间坐标或测量物体的几何特性如距离、角度、半径等，这些操作都需要以拾取作为实现的基础。OpenGL为了解决拾取问题，提供了一种基于名字堆栈和命中记录的选择机制。在OpenGL中,拾取物体是利用拾取矩阵和投影变换，将拾取的范围限制在鼠标热点的有效区中，一旦触发鼠标事件就进入选择模式并将有效区初始化，最后利用拾取矩阵拾取有效区内的物体。有效区的定义由glPick2Matix()函数来完成。一旦拾取成功，就以记录的形式返回与拾取物体相关的信息，并生成一个记录表示一个物体被命中。这种物体拾取方法非常简单，不需要写很多代码。

在使用OpenGL工具包开发图形处理系统时，物体的拾取有多种方法，其中包括OpenGL提供的选择机制、射线拾取法、重绘式拾取法等。本文采用OpenGL本身提供的选择机制来拾取对象，突出OpenGL工具包在屏幕对象的拾取方面的优势。 关 键 词：OpenGL；计算机应用；拾取算法

1

Abstract

In most cases, one important feature of graphics processing system is picking, which allow users to select objects by mouse, and to modify the their attributes, such as gemetry mesh or angle and so on. In order to solve the problem, pick OpenGL provides a name on the stack and hit record choice mechanism. In the OpenGL and pickobject is using the loot matrix and projection transformation, and will gather in the limits of the mouse, effective once entered the mouse event trigger mode choice and will be effective area, finally using initialization gleaned matrix pick objects in the area of effective. The definition of effective glPick2Matix () function to finish. Once pick success, to return to pick the record object relevant

information, and to create a record, says an object to be hit. This object pick method is very simple, need not write many code.

In the use of graphics processing system development OpenGL toolkit objects, pick a variety of methods, including OpenGL provide choice mechanism, ray pick, redrawn type gather method, etc. Based on the mechanism of OpenGL itself to provide choice pickup, outstanding OpenGL toolkit objects in the screen in the object.