如何在OpenGL 3.3中修复黑屏输出

How to fix black screen output in OpenGL 3.3

本文关键字：输出 OpenGL      更新时间：2023-10-16

我在使用 OpenGL 和 C++ 的项目中遇到黑屏。我需要帮助，了解我在哪里出错了，将红色三角形渲染到屏幕上。

我尝试检查顶点和片段着色器中的错误。

#include <GLglew.h>
#include <GLGL.h>
#include <GLFWglfw3.h>
#include <iostream>
#include <string>
using namespace std;
unsigned int CreateShader(int type, const string shaderSource) {
unsigned int shader = glCreateShader(type);
const char *src = shaderSource.c_str();
glShaderSource(shader, 1, &src, NULL);
glCompileShader(shader);
int result;
glGetShaderiv(shader, GL_COMPILE_STATUS, &result);
if (result == GL_FALSE) {
int length;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
char *message = (char*)alloca(length * sizeof(char));
glGetShaderInfoLog(shader, length, &length, message);
cout << "Failed to compile " << (type == GL_VERTEX_SHADER ? "vertex shader " : "fragment shader ") << endl;
cout << message << endl;
}

return shader;
}
unsigned int CreateProgram(const string vertexShader, const string fragmentShader) {
unsigned int program = glCreateProgram();
unsigned int vs = CreateShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CreateShader(GL_FRAGMENT_SHADER, fragmentShader);
glAttachShader(program, vs);
glAttachShader(program, fs);
glDeleteShader(vs);
glDeleteShader(fs);
glLinkProgram(program);
glValidateProgram(program);
return program;
}
int main() {
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow *window = glfwCreateWindow(800, 600, "window", NULL, NULL);
glfwMakeContextCurrent(window);
glewInit();
if (glewInit() != GLEW_OK) {
cout << "Glew initialization Failed! " << endl;
glfwTerminate();
return -1;
}
float positions[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f,
};
cout << "Made By Rial Seebran" << endl;
cout << glfwGetVersionString() << endl;

unsigned int VAO;
unsigned int VBO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(positions), positions, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
const string vertexShader =
"#version 330 coren"
"layout (location = 0) in vec3 position;n"
"void main() {n"
"gl_Position = vec4(position, 0.0f);n"
"}n";
const string fragmentShader =
"#version 330 coren"
"layout (location = 0) out vec4 color;n"
"void main() {n"
"color = vec4(1.0f, 0.0f, 0.0f, 1.0f);n"
"}n";
unsigned int program = CreateProgram(vertexShader, fragmentShader);

while (!glfwWindowShouldClose(window)) {
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
glBindVertexArray(VAO);
glDrawArrays(GL_ARRAY_BUFFER, 0, 3);
glBindVertexArray(0);
glfwPollEvents();
glfwSwapBuffers(window);
}
glfwTerminate();
return 0;
}

我期待在用蓝色背景指定的坐标处绘制一个红色三角形。

要glDrawArrays的第一个参数必须是基元类型。
它必须是GL_TRIANGLES而不是GL_ARRAY_BUFFER：


glDrawArrays(GL_ARRAY_BUFFER, 0, 3);glDrawArrays(GL_TRIANGLES, 0, 3);

OpenGL 枚举器常量GL_ARRAY_BUFFER不是此参数的可接受值，将导致GL_INVALID_ENUM错误(错误可以通过glGetError获得)。

当剪辑空间坐标转换为规范化设备空间时，x、y和z分量被w分量除以。 这意味着gl_Position的w组件必须设置为 1.0 而不是 0.0：


gl_Position = vec4(position, 0.0f);gl_Position = vec4(position, 1.0);

Glew 可以通过glewExperimental = GL_TRUE;启用其他扩展。请参阅GLEW文档，其中说：

GLEW 从图形驱动程序获取有关支持的扩展的信息。但是，实验性或预发布驱动程序可能不会通过标准机制报告每个可用的扩展，在这种情况下，GLEW 将报告它不受支持。为了规避这种情况，可以通过在调用glewInit()之前将其设置为GL_TRUE来打开glewExperimental全局开关，从而确保所有具有有效入口点的分机都将公开。

glewExperimental = GL_TRUE;
if ( glewInit() != GLEW_OK ) {
cout << "Glew initialization Failed! " << endl;
glfwTerminate();
return -1;
}
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