長さ（および幅。IDEでわかりやすくするため）を許してください。ただし、目的は最新のVBOおよびGLSLの単純なHello Worldであるため、コードの全長を表示することを考えました。
当初はhttp://people.freedesktop.org/~idr/OpenGL_tutorials/02-GLSL-hello-world.pdfに基づいていました
重要な点は、単一のエラーメッセージや警告が出力されないことです。printfsがたくさんあることがわかります（実際には、ほとんどすべてのコードがエラーを検出しようとしています）。
コンパイルは-std=c99 -pedantic -O0 -g -Wall（警告なし）で実行されるため、コンパイラエラーの余地もあまりありません。
私はピンポイントで注意を向けました
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
と
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
（後者は私がまだ完全に理解していないコードの唯一の部分です;最もあいまいな機能'これまで'）
情報ログは何も出力せず、シェーダーが意図的に無効にされた場合、通常どおり正常なテキストを印刷します。したがって、シェーダーの文字列の割り当てでもコンパイルでもありません。
空白の画面を印刷する可能性のあるものを見ることができますか？
glDrawArraysがGL_POINTSとともに使用されている場合は中央に単一のドットを出力し、glClearの前に適切なglClearColorが付いている場合は色が変わります。
#include "SDL.h" // Window and program management
#include "Glee.h" // OpenGL management; Notice SDL's OpenGL header is not included
#include <stdbool.h> // C99 bool
void initGL(void);
void drawGL(void);
int main (int argc, char **argv) {
// Load the SDL library; Initialize the Video Subsystem
if (SDL_Init(SDL_INIT_VIDEO) < 0 ) printf("SDL_Init fail: %s\n", SDL_GetError());
/* Video Subsystem: set up width, height, bits per pixel (0 = current display's);
Create an OpenGL rendering context */
if (SDL_SetVideoMode(800, 600, 0, SDL_OPENGL) == NULL) printf("SDL_SetVideoMode fail: %s\n", SDL_GetError());
// Title and icon text of window
SDL_WM_SetCaption("gl", NULL);
// Initialize OpenGL ..
initGL();
bool done = false;
// Loop indefinitely unless user quits
while (!done) {
// Draw OpenGL ..
drawGL();
// Deal with SDL events
SDL_Event sdl_event;
do {
if ( sdl_event.type == SDL_QUIT || (sdl_event.type == SDL_KEYDOWN && sdl_event.key.keysym.sym == SDLK_ESCAPE)) {
done = true;
break;
}
} while (SDL_PollEvent(&sdl_event));
}
// Clean SDL initialized systems, unload library and return.
SDL_Quit();
return 0;
}
GLuint program;
GLuint buffer;
#define BUFFER_OFFSET(i) ((char *)NULL + (i))
void initGL(void) {
// Generate 1 buffer object; point its name (in uint form) to *buffer.
glGenBuffers(1, &buffer); if(glGetError()) printf("glGenBuffers error\n");
/* bind the named (by a uint (via the previous call)) buffer object to target GL_ARRAY_BUFFER (target for vertices)
apparently, one object is bound to a target at a time. */
glBindBuffer(GL_ARRAY_BUFFER, buffer); if(glGetError()) printf("glBindBuffer error\n");
/* Create a data store for the current object bound to GL_ARRAY_BUFFER (from above), of a size 8*size of GLfloat,
with no initial data in it (NULL) and a hint to the GrLib that data is going to be modified once and used a
lot (STATIC), and it's going to be modified by the app and used by the GL for drawing or image specification (DRAW)
Store is not mapped yet. */
glBufferData( GL_ARRAY_BUFFER, 4 * 2 * sizeof(GLfloat), NULL, GL_STATIC_DRAW); if(glGetError()) printf("glBufferData error\n");
/* Actually map to the GL client's address space the data store currently bound to GL_ARRAY_BUFFER (from above).
Write only. */
GLfloat *data = (GLfloat *) glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY); if (!*data) printf("glMapBuffer error1\n"); if(glGetError()) printf("glMapBuffer error2\n");
// Apparently, write some data on the object.
data[0] = -0.75f; data[1] = -0.75f; data[2] = -0.75f; data[3] = 0.75f;
data[4] = 0.75f; data[5] = 0.75f; data[6] = 0.75f; data[7] = -0.75f;
// Unmap the data store. Required *before* the object is used.
if(!glUnmapBuffer(GL_ARRAY_BUFFER)) printf("glUnmapBuffer error\n");
// Specify the location and data format of an array of generic vertex attributes ..
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
// the shaders source
GLchar *vertex_shader_code[] = { "void main(void) { gl_Position = gl_Vertex; }"};
GLchar *fragment_shader_code[] = { "void main(void) { gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0); }"};
/* Create an empty shader object; used to maintain the source string; intended to run
on the programmable vertex processor; GL_SHADER_TYPE is set to GL_VERTEX_SHADER
(e.g. for use on glGetShaderiv)*/
GLuint vs = glCreateShader(GL_VERTEX_SHADER); if (!vs) printf("glCreateShader fail\n");
/* Set the source code in vs; 1 string; GLchar **vertex_shader_code array of pointers to strings,
length is NULL, i.e. strings assumed null terminated */
glShaderSource(vs, 1, (const GLchar **) &vertex_shader_code, NULL); if(glGetError()) printf("glShaderSource error\n");
// Actually compile the shader
glCompileShader(vs); GLint compile_status; glGetShaderiv(vs, GL_COMPILE_STATUS, &compile_status); if (compile_status == GL_FALSE) printf("vertex_shader_code compilation fail\n"); if(glGetError()) printf("glGetShaderiv fail\n");
// same
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER); if (!fs) printf("glCreateShader fail\n");
// same
glShaderSource(fs, 1, (const GLchar **) &fragment_shader_code, NULL); if(glGetError()) printf("glShaderSource error\n");
// same
glCompileShader(fs); glGetShaderiv(fs, GL_COMPILE_STATUS, &compile_status); if (compile_status == GL_FALSE) printf("fragment_shader_code compilation fail\n"); if(glGetError()) printf("glGetShaderiv fail\n");
/* Empty program for later attachment of shaders; it provides management mechanism for them.
Shaders can be compiled before or after their attachment. */
program = glCreateProgram(); if(!program) printf("glCreateProgram fail1\n"); if(glGetError()) printf("glCreateProgram fail2\n");
/* Attach shaders to program; this could be done before their compilation or their association with code
Destined to be linked together and form an executable. */
glAttachShader(program, vs); if(glGetError()) printf("glAttachShader fail1\n");
glAttachShader(program, fs); if(glGetError()) printf("glAttachShader fail2\n");
// Link the program; vertex shader objects create an executable for the vertex processor and similarly for fragment shaders.
glLinkProgram(program); GLint link_status; glGetProgramiv(program, GL_LINK_STATUS, &link_status); if (!link_status) printf("linking fail\n"); if(glGetError()) printf("glLinkProgram fail\n");
/* Get info log, if any (supported by the standard to be empty).
It does give nice output if compilation or linking fails. */
GLchar infolog[2048];
glGetProgramInfoLog(program, 2048, NULL, infolog); printf("%s", infolog); if (glGetError()) printf("glGetProgramInfoLog fail\n");
/* Install program to rendering state; one or more executables contained via compiled shaders inclusion.
Certain fixed functionalities are disabled for fragment and vertex processors when such executables
are installed, and executables may reimplement them. See glUseProgram manual page about it. */
glUseProgram(program); if(glGetError()) printf("glUseProgram fail\n");
}
void drawGL(void) {
// Clear color buffer to default value
glClear(GL_COLOR_BUFFER_BIT); if(glGetError()) printf("glClear error\n");
// Render the a primitive triangle
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); if(glGetError()) printf("glDrawArrays error\n");
SDL_GL_SwapBuffers();
}