1）我是否正确理解，要使用顶点数组或VBO进行绘制，我需要所有属性在着色器程序链接之前调用glBindAttribLocation，或者在着色器程序成功链接后调用glGetAttribLocation，然后使用glVertexAttribPointer中的绑定/获得的索引和 glEnableVertexAttribArray 调用？
更具体地说：这三个函数 - glGetAttribLocation、glVertexAttribPointer 和 glEnableVertexAttribArray - 它们都有一个名为“index”的输入参数。这三个的“索引”是相同的吗？它和 glGetAttribLocation 返回的结果是一样的吗？
如果是：
2）我在 OS X 上遇到了一个问题，我在这里描述了它：https://stackoverflow.com/questions/28093919/using-default-attribute-location-doesnt-work-on-osx-osx-opengl-bug https://stackoverflow.com/questions/28093919/using-default-attribute-location-doesnt-work-on-osx-osx-opengl-bug，但遗憾的是没有得到任何回复。
问题是，根据我绑定到属性的属性位置，我在屏幕上看到或看不到任何内容。我仅在运行 OS X 10.9.5 的 MacBook Pro 上看到此行为；我尝试在 Linux 和 Windows 上运行相同的代码，它似乎可以在这些平台上运行，与我的属性绑定到的位置无关。
这是一个显示问题的代码示例（应该在屏幕上绘制一个红色三角形）：
#include <iostream>
#include <GLFW/glfw3.h>
GLuint global_program_object;
GLint global_position_location;
GLint global_aspect_ratio_location;
GLuint global_buffer_names[1];
int LoadShader(GLenum type, const char *shader_source)
{
GLuint shader;
GLint compiled;
shader = glCreateShader(type);
if (shader == 0)
return 0;
glShaderSource(shader, 1, &shader_source, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
if (!compiled)
{
GLint info_len = 0;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &info_len);
if (info_len > 1)
{
char* info_log = new char[info_len];
glGetShaderInfoLog(shader, info_len, NULL, info_log);
std::cout << "Error compiling shader" << info_log << std::endl;
delete info_log;
}
glDeleteShader(shader);
return 0;
}
return shader;
}
int InitGL()
{
char vertex_shader_source[] =
"attribute vec4 att_position; \n"
"attribute float dummy;\n"
"uniform float uni_aspect_ratio; \n"
"void main() \n"
" { \n"
" vec4 test = att_position * dummy;\n"
" mat4 mat_projection = \n"
" mat4(1.0 / uni_aspect_ratio, 0.0, 0.0, 0.0, \n"
" 0.0, 1.0, 0.0, 0.0, \n"
" 0.0, 0.0, -1.0, 0.0, \n"
" 0.0, 0.0, 0.0, 1.0); \n"
" gl_Position = att_position; \n"
" gl_Position *= mat_projection; \n"
" } \n";
char fragment_shader_source[] =
"void main() \n"
" { \n"
" gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); \n"
" } \n";
GLuint vertex_shader;
GLuint fragment_shader;
GLuint program_object;
GLint linked;
vertex_shader = LoadShader(GL_VERTEX_SHADER , vertex_shader_source );
fragment_shader = LoadShader(GL_FRAGMENT_SHADER, fragment_shader_source);
program_object = glCreateProgram();
if(program_object == 0)
return 1;
glAttachShader(program_object, vertex_shader );
glAttachShader(program_object, fragment_shader);
// Here any index except 0 results in observing the black screen
glBindAttribLocation(program_object, 1, "att_position");
glLinkProgram(program_object);
glGetProgramiv(program_object, GL_LINK_STATUS, &linked);
if(!linked)
{
GLint info_len = 0;
glGetProgramiv(program_object, GL_INFO_LOG_LENGTH, &info_len);
if(info_len > 1)
{
char* info_log = new char[info_len];
glGetProgramInfoLog(program_object, info_len, NULL, info_log);
std::cout << "Error linking program" << info_log << std::endl;
delete info_log;
}
glDeleteProgram(program_object);
return 1;
}
global_program_object = program_object;
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glUseProgram(global_program_object);
global_position_location = glGetAttribLocation (global_program_object, "att_position");
global_aspect_ratio_location = glGetUniformLocation(global_program_object, "uni_aspect_ratio");
GLfloat vertices[] = {-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f};
glGenBuffers(1, global_buffer_names);
glBindBuffer(GL_ARRAY_BUFFER, global_buffer_names[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 9, vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
return 0;
}
void Render()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glUseProgram(global_program_object);
glBindBuffer(GL_ARRAY_BUFFER, global_buffer_names[0]);
glVertexAttribPointer(global_position_location, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(global_position_location);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(global_position_location);
glUseProgram(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
void FreeGL()
{
glDeleteBuffers(1, global_buffer_names);
glDeleteProgram(global_program_object);
}
void SetViewport(int width, int height)
{
glViewport(0, 0, width, height);
glUseProgram(global_program_object);
glUniform1f(global_aspect_ratio_location, static_cast<GLfloat>(width) / static_cast<GLfloat>(height));
}
int main(void)
{
GLFWwindow* window;
if (!glfwInit())
return -1;
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
InitGL();
// Double the resolution to correctly draw with Retina display
SetViewport(1280, 960);
while (!glfwWindowShouldClose(window))
{
Render();
glfwSwapBuffers(window);
glfwPollEvents();
}
FreeGL();
glfwTerminate();
return 0;
}
您认为这看起来像是一个错误吗？任何人都可以复制它吗？如果是错误，我应该在哪里报告？
附：
我也尝试过 SDL 而不是 GLFW，行为是相同的......
