1. vertShader.glsl（顶点着色器代码）：

#version 460

void
main (void)
{
	if (gl_VertexID == 0)
		gl_Position = vec4 (0.25, -0.25, 0.0, 1.0);
	else if (gl_VertexID == 1)
		gl_Position = vec4 (-0.25, -0.25, 0.0, 1.0);
	else
		gl_Position = vec4 (0.25, 0.25, 0.0, 1.0);
}

2. Utils.h（读取着色器代码）

Utils.h

#pragma once

#include <fstream>
#include <iostream>
#include <string>

class Utils {
public:

	using string   = std::string;
	using ifstream = std::ifstream;

	static string readShaderSource (const char *filePath)
	{
		string content;

		ifstream fileStream (filePath, std::ios::in);

		string line = "";

		while (!fileStream.eof()) {
			std::getline (fileStream, line);
			content.append (line += "\n");
		}
		fileStream.close();
		return content;
	}
};

3. main函数

需要注意的是，glDrawArrays (GL_TRIANGLES, 0, 3);中指定的类型是三角形GL_TRIANGLES。

#include "Utils.h"

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>

using namespace std;

constexpr int numVAOs = 1;

GLuint renderingProgram;
GLuint vao[numVAOs];

GLuint
createShaderProgram ()
{
	Utils::string vShaderString = Utils::readShaderSource ("vertShader.glsl");
	const char *vshaderSource	= vShaderString.c_str();

	const char *fshaderSource = "#version 460 \n"
								"out vec4 color; \n"
								"void main(void) \n"
								"{ color = vec4(0.0, 0.0, 1.0, 1.0); }";

	GLuint vShader = glCreateShader (GL_VERTEX_SHADER);
	GLuint fShader = glCreateShader (GL_FRAGMENT_SHADER);

	glShaderSource (vShader, 1, &vshaderSource, NULL);
	glShaderSource (fShader, 1, &fshaderSource, NULL);
	glCompileShader (vShader);
	glCompileShader (fShader);

	GLuint vfProgram = glCreateProgram();
	glAttachShader (vfProgram, vShader);
	glAttachShader (vfProgram, fShader);
	glLinkProgram (vfProgram);

	return vfProgram;
}

void
display (GLFWwindow *window, double currTime)
{
	glUseProgram (renderingProgram);
	glPointSize (5.0);
	glDrawArrays (GL_TRIANGLES, 0, 3);
}

void
init (GLFWwindow *window)
{
	renderingProgram = createShaderProgram();
	glGenVertexArrays (numVAOs, vao);
	glBindVertexArray (vao[0]);
}

int
main (int argc, char *argv[])
{
	if (!glfwInit()) {
		return -1;
	}

	glfwWindowHint (GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint (GLFW_CONTEXT_VERSION_MINOR, 6);

	GLFWwindow *window = glfwCreateWindow (600, 600, "Chapter2 - program1", nullptr, nullptr);
	glfwMakeContextCurrent (window);

	int errorCode = glewInit();
	if (errorCode != GLEW_OK) {
		cerr << "Error: " << glewGetErrorString (errorCode) << endl;
		return -1;
	}
	glfwSwapInterval (1);

	init (window);

	while (!glfwWindowShouldClose (window)) {
		display (window, glfwGetTime());
		glfwSwapBuffers (window);
		glfwPollEvents();
	}

	glfwDestroyWindow (window);
	glfwTerminate();

	return 0;
}