NeHe OpenGL Lesson24 – Tokens, Extensions, Scissor Testing And TGA Loading

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原文链接：http://www.cnblogs.com/open-coder/archive/2012/08/23/2653277.html

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本文介绍了如何使用OpenGL API提取并解析OpenGL扩展，包括显示卡的硬件信息如渲染器名称、供应商名称、版本号和扩展名。此外，还详细讲解了剪切测试的概念和应用，通过设置剪切区域，限制绘制操作只在屏幕上的特定矩形区域内进行。

This sample shows us how to extract the OpenGL extensions into tokens and scissor testing.
In the masking example, I already wrote some code of loading TGA textures. But here, another TGA loading also provided.
In addition to get the OpenGL extensions, we could also get some information about our display card hardware information with OpenGL API functions. We could get the where our display card render name, vendor name, version number and extensions like this:

char* render = (char *)glGetString(GL_RENDERER));
char* vendor = (char *)glGetString(GL_VENDOR));
char* version = glGetString(GL_VERSION));
// ext seperate by ' ' space character
char* ext = (char *)glGetString(GL_EXTENSIONS)

Scissor testing will let us draw something only in a rectangle area on the screen. The following code used to set up scissor testing:

glScissor(x, y, width, height);
glEnable(GL_SCISSOR_TEST);    
 
// draw something here
// ...
 
glDisable(GL_SCISSOR_TEST);

glScissor defines a rectangle, called the scissor box,in window coordinates.The first two arguments,x and y,specify the lower left corner of the box.width and height specify the width and height of the box. For more details about this function, you could check to http://www.opengl.org/sdk/docs/man/xhtml/glScissor.xml.

The full source code could be downloaded from here.

转载于:https://www.cnblogs.com/open-coder/archive/2012/08/23/2653277.html