OpenGL: Starting with the Shading Language-0

since: 2012/05/25
update: 2012/05/25
reference:
Tutorial - Getting Started with the OpenGL Shading Language (GLSL)

前置準備

A. 說明:
      本文章內容沿用 OpenGL: Basic Setup 所建立的專案, 來加入新的檔案.
       新加入的檔案來源皆從 joshbeam.com GLSL  取得.

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B. 下載檔案與專案調整: (前置準備)
      1. 下載檔案: glsl_lighting-1.tar.gz

      2. 解壓縮後, 將所有 *.c 的檔案皆改成 *.cpp (因為我們使用 C++ 的專案), 
          再將 main.cpp 更名成 GLSLmain.cpp (防止專案中名稱重複).

      3. 接著將所有檔案(除了 Makefile 與 README.txt), 包含 data 資料夾,
          全部 copy 到專案目錄下. 

      4. 專案調整:
         a. 在專案建立一個群組: GLSL, 將剛剛 copy 到專案下的檔案全部加到群組裡.

         b. 將之前的 main function (如果有的話) 更改名稱, 不要成為預設的程式入口.
             開啓 main.cpp 檔案, 修改如下:
            // main function for loading 3d models
            //int main(int argc, char * argv[])
            int main_forLoading3dMmodels(int argc, char * argv[])
            {
            ....
            }

         c. 檢查工作目錄:
             (1). 點選專案左上方的 Scheme, 選取: "Edit Scheme..."
             (2). 接著,  先選取左邊的 "Run MyOpenGL Debug", 再選取右邊的: "Options":
                     勾選: Use Custom working directory:
                                /Lanli/RD/Projects/OpenGL/MyOpenGL
                     > OK

      5. 分析專案內容:
         執行 "Product" > "Analyze":
         > 修正相關錯誤:

*****************************************************

         a. opengl.h // line 34
             message: 'GL/gl.h' file not found

             修正:
#ifndef __OPENGL_H__
#define __OPENGL_H__

//@fixed for Apple:'GL/gl.h' file not found
#ifndef APPLE
#define APPLE
#endif

#ifdef APPLE
    #include <OpenGL/gl.h>
    #include <OpenGL/glext.h>
    #include <GLUT/glut.h>
#else
    #include <GL/gl.h>
    #include <GL/glext.h>
    #include <GL/glut.h>
#endif /* APPLE */

#endif /* __OPENGL_H__ */

*****************************************************

         b. scene.cpp 
            // line 67
            message: Assigning to 'float *' from incompatible type 'void *';

             修正:
    /* generate vertex data */
    //@fixed: Assigning to 'float *' from incompatible type 'void *';
    //v = malloc(sizeof(float) * size);
    v = (float *)malloc(sizeof(float) * size);

            // line 127
            message: Assigning to 'char *' from incompatible type 'void *';

             修正:
        /* get the program info log */
        glGetProgramiv(g_program, GL_INFO_LOG_LENGTH, &length);
        //@fixed: Assigning to 'char *' from incompatible type 'void *';
        //log = malloc(length);
        log = (char *)malloc(length);
        glGetProgramInfoLog(g_program, length, &result, log);

*****************************************************

         c. shader.cpp
            // line 53, message:
            Cannot initialize a variable of type 'char *' with an rvalue of type 'void *'

             修正:
    /* read the entire file into a string */
    while((tmp = fread(buf, 1, blockSize, fp)) > 0) {
        //@fixed: Cannot initialize a variable of type 'char *' with an rvalue of type 'void *'
        //char *newSource = malloc(sourceLength + tmp + 1);
        char *newSource = (char *)malloc(sourceLength + tmp + 1);
        ....

            // line 110
            message: Assigning to 'char *' from incompatible type 'void *';

             修正:
        /* get the shader info log */
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
        //@fixed: Assigning to 'char *' from incompatible type 'void *';
        //log = malloc(length);
        log = (char *)malloc(length);