用 SDL2 和 OpenGL 绘制一个三角形

Question

我正在尝试用C++制作游戏，并将SDL2与OpenGL一起使用。 当我尝试使用 GLEW 在 opengl 上下文中绘制一个简单的三角形时，没有任何显示。我以前没有使用过opengl.
这是我的代码：

#define GLEW_STATIC
#include <GL/glew.h>
#include <GL/gl.h>
#include <SDL2/SDL.h>
#include <iostream>

我有Fragment和Vertex着色器，但StackOverflow说我有太多的代码而没有足够的细节。

int main(int argc, char *argv[])
{
SDL_Init(SDL_INIT_EVERYTHING);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
SDL_Window* window = SDL_CreateWindow("GAME", 100, 100, 800, 600, SDL_WINDOW_OPENGL);
SDL_GLContext context = SDL_GL_CreateContext(window);
glewExperimental = GL_TRUE;
glewInit();
GLuint vertexBuffer;
glGenBuffers(1, &vertexBuffer);
printf("%un", vertexBuffer);
float vertices[] = {
0.0f, 0.5f,
0.5f, -0.5f,
-0.5f, -0.5f
};
GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER,vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexSource, NULL);
glCompileShader(vertexShader);

GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
glCompileShader(fragmentShader);
GLuint shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glBindFragDataLocation(shaderProgram, 0, "outColor");
glLinkProgram(shaderProgram);
glUseProgram(shaderProgram);
GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(posAttrib);
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
SDL_Event event;
while(true)
{
if (SDL_PollEvent(&event))
{
if(event.type == SDL_QUIT) break;
}
SDL_GL_SwapWindow(window);
glClearColor(0.2578125f,  0.52734375f,  0.95703125f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
}
SDL_GL_DeleteContext(context);
SDL_Quit();
return 0;
}

我用g++ src/main.cpp glad/src/glad.c -I./glad/include -o main -lGL -lglfw -lGLEW -ldl -lSDL2 -ldl --std=c++14编译这个

Answer 1

顶点规范存储在顶点数组对象中。glVertexAttribPointer和glEnableVertexAttribArray当前绑定的 VAO 中的设置状态。因此，您必须在顶点规范之前创建并绑定 VAO。

GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(posAttrib);