【Note】2012.10.3

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Oct 3 2012<<<<<<<<<<<<<<<<<<<<<<<<<<<<

1. Bresenham's line algorithm（网上找的一个实现）

void PlotLine(int x1,int x2,int y1,int y2, char r, char g, char b)
{
    int xinc1,yinc1;
    int xinc2,yinc2;
    int deltax = abs(x2 - x1);        // The difference between the x's
    int deltay = abs(y2 - y1);        // The difference between the y's
    int x = x1;                       // Start x off at the first pixel
    int y = y1;
    int den=0,num=0,numadd=0,numpixels=0,curpixel=0;                       // Start y off at the first pixel


    if (x2 >= x1)                 // The x-values are increasing
    {
        xinc1 = 1;
        xinc2 = 1;
    }
    else                          // The x-values are decreasing
    {
        xinc1 = -1;
        xinc2 = -1;
    }                                                        

    if (y2 >= y1)                 // The y-values are increasing
    {
        yinc1 = 1;
        yinc2 = 1;
    }
    else                          // The y-values are decreasing
    {
        yinc1 = -1;
        yinc2 = -1;
    }

    if (deltax >= deltay)         // There is at least one x-value for every y-value
    {
        xinc1 = 0;                  // Don't change the x when numerator >= denominator
        yinc2 = 0;                  // Don't change the y for every iteration
        den = deltax;
        num = deltax >>1;
        numadd = deltay;
        numpixels = deltax;         // There are more x-values than y-values
    }
    else                          // There is at least one y-value for every x-value
    {
        xinc2 = 0;                  // Don't change the x for every iteration
        yinc1 = 0;                  // Don't change the y when numerator >= denominator
        den = deltay;
        num = deltay >>1;
        numadd = deltax;
        numpixels = deltay;         // There are more y-values than x-values
    }


    for (curpixel = 0; curpixel <= numpixels; curpixel++)
    {
        DrawPixel(screen, x, y, r, g, b);
        num += numadd;              // Increase the numerator by the top of the fraction
        if (num >= den)             // Check if numerator >= denominator
        {
            num -= den;               // Calculate the new numerator value
        x += xinc1;               // Change the x as appropriate
            y += yinc1;               // Change the y as appropriate
        }

        x += xinc2;                 // Change the x as appropriate
        y += yinc2;                 // Change the y as appropriate
    }
}

2. Reyes（Rendering everything you ever see）渲染架构，分为下面几个步骤:

• Bound，求包围盒
• Split，大的物体划分出小物体，方便将看不到的部分扔掉，同时一个细分网格不会包含太多细分面
• Dice，细分，存储到细分网格中
• Shade
• Sample

参考：http://www.steckles.com/reyes1.html

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Oct 10 2012<<<<<<<<<<<<<<<<<<<<<<<<<<<<

1. error LNK2022: metadata operation failed (8013118D) : Inconsistent layout information in duplicated types

     问题原因在于使用clr选项编译时，编译规则要比纯C++严格。当一个类型有个定义，但是内部结构不一致、大小不一致，就会出现该错误提示。

     问题解决：出现该问题是使用了一个第三方库的一个类型MString，在有些问题中使用时没问题，有些就报错，后来发现是有几个头文件没加进来导致的

     参考：http://social.msdn.microsoft.com/Forums/en/vclanguage/thread/079a2b60-951d-4e84-affc-8d8bfaf87cab

2. 调用第三方库函数，同一个类，有些函数可以调用，有些函数却报link错误，找不到符号，怀疑是类实现在多个lib中

    dumpbin发现，该类确实在多个lib中，引入lib，问题解决

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Oct 12 2012<<<<<<<<<<<<<<<<<<<<<<<<<<<<

1. Autoconf是linux上用来生成自动编译、安装脚本的工具

框架图如下：

下面介绍使用autoconf自动生成编译脚本的流程：

1. 运行autoscan命令，生成configure.scan
2. 将configure.scan 文件重命名为configure.in，并修改configure.in文件
   主要修改AM_INIT_AUTOMAKE(package, version [, no-define])（第一个参数生成的程序名，第二个为版本）与AC_OUTPUT（对每一个要输出的Makefile都要添加）
   示例：
   

   #                                -*- Autoconf -*-
   # Process this file with autoconf to produce a configure script.
   
   AC_PREREQ(2.59)
   AC_INIT(test, 1.0, normalnotebook@126.com)
   AC_CONFIG_SRCDIR([src/ModuleA/apple/core/test.c])
   AM_CONFIG_HEADER(config.h)
   AM_INIT_AUTOMAKE(test,1.0)
   
   # Checks for programs.
   AC_PROG_CC
   # Checks for libraries.
   # FIXME: Replace `main' with a function in `-lpthread':
   AC_CHECK_LIB([pthread], [pthread_rwlock_init])
   AC_PROG_RANLIB
   # Checks for header files.
   # Checks for typedefs, structures, and compiler characteristics.
   # Checks for library functions.
   AC_OUTPUT([Makefile
           src/lib/Makefile
           src/ModuleA/apple/core/Makefile
           src/ModuleA/apple/shell/Makefile
           ])
           

3. 在工程目录下新建Makefile.am文件，并在需要编译的子目录也新建makefile.am文件（以下是一个示例文件）
   

   AM_CFLAGS = $(X_CFLAGS)
   ## Add warnings for gcc-3.4
   AM_CFLAGS += -Wall -Wunused -Wimplicit -Wreturn-type
   AM_CFLAGS += -Wdeclaration-after-statement -Wno-unknown-pragmas
   AM_CFLAGS += -Wmissing-prototypes -Wmissing-declarations -Wparentheses
   AM_CFLAGS += -Wswitch -Wtrigraphs -Wpointer-arith -Wcast-qual
   AM_CFLAGS += -Wcast-align -Wwrite-strings -Wold-style-definition
   
   LDADD = $(X_LIBS) -lX11 -lXmu $(X_EXTRA_LIBS)
   
   EXTRA_DIST = pdfopen-AR-7-and-8.c
   
   bin_PROGRAMS = pdfopen pdfclose
   
   pdfopen_SOURCES = pdfopen.c sendx.c utils.c sendx.h xpdfopen.h utils.h
   
   pdfclose_SOURCES = pdfclose.c sendx.c utils.c sendx.h xpdfopen.h utils.h

4. 在工程目录下新建NEWS、 README、 ChangeLog 、AUTHORS文件
5. 将/usr/share/automake-1.X/目录下的depcomp和complie文件拷贝到本目录下
6. 运行aclocal命令
7. 运行autoconf命令
8. 运行automake -a命令，生成Makefile.in
9. 运行autoheader命令，生成config.h.in
10. 运行./confiugre脚本

2. 前缀树：trie或者prefix tree(前缀树),是一种有序树数据结构,它通常被存储在一个以字符串为关键字的联合数组中。于二叉搜索树不同，在树里没有结点存储与结点相关联的关键字。它是用它在树中的位置展示与它相关的关键字。

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Oct 19 2012<<<<<<<<<<<<<<<<<<<<<<<<<<<<

1. 编译boost时发现，boost使用jam来编译整个工程，而不是使用make。jam简单，而且跨平台。

参考：http://www.freetype.org/jam/index.html

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Oct 24 2012<<<<<<<<<<<<<<<<<<<<<<<<<<<<

1. Consider the "right-end" of curve f(b) and the "left-end" of curve g(m). If f(b) and g(m) are equal as shown in the above figure, we shall say curves f() and g() are C⁰continuous at f(b)=g(m). If for all i <= k, the i-th derivatives at f(b) and g(m) are equal, we shall say that the curves are C^k continuous at point f(b)=g(m).