skein/hello.cpp

192 lines
4.6 KiB
C++

// To compile on Windows
// Install GLFW 3.3.8
// https://www.glfw.org/download.html
// Install GLEW 2.2.0
// https://github.com/nigels-com/glew/releases/tag/glew-2.2.0
//
// extract the downloaded .zip files to "C:/libs"; this is currently expected
// by our CMakeLists.txt.
// Install CMake
// https://cmake.org/download
// Add to PATH for all users
// from project root:
// mkdir build
// cd build
// cmake ..
// cmake --build .
// The last step compiles the executable - this can also be done from Visual
// Studio
// To run in VS
// Set startup project in Solution Explorer
// Press F5 to run
//
// To compile on Arch Linux
//
// Install dependencies
// sudo pacman -S glfw mesa glew
//
// Build
// cmake ..
// cmake --build .
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <chrono>
std::string readFile(const std::string& filePath)
{
std::ifstream fileStream(filePath, std::ios::in);
if (!fileStream.is_open())
{
std::cerr << "Could not read file " << filePath <<
". File does not exist." << std::endl;
return "";
}
std::stringstream sstr;
sstr << fileStream.rdbuf();
fileStream.close();
return sstr.str();
}
GLuint compileShader(const std::string& shaderPath, GLenum shaderType)
{
GLuint shader;
GLint success;
std::string shaderSource = readFile(shaderPath);
const char* source = shaderSource.c_str();
shader = glCreateShader(shaderType);
glShaderSource(shader, 1, &source, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
if (!success)
{
GLchar infoLog[512];
glGetShaderInfoLog(shader, 512, NULL, infoLog);
std::cerr << "shader compilation failed" << std::endl
<< infoLog << std::endl;
}
return shader;
}
std::chrono::steady_clock::time_point startTime = std::chrono::steady_clock::now();
float getTime()
{
std::chrono::steady_clock::time_point now = std::chrono::steady_clock::now();
std::chrono::duration<float> timeSpan = std::chrono::duration_cast<std::chrono::duration<float>>(now - startTime);
return timeSpan.count();
}
int main()
{
// Set up GLFW, OpenGL and GLEW.
if (!glfwInit())
return -1;
GLFWwindow* window = glfwCreateWindow(640, 480, "Hello Triangle", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK)
{
std::cerr << "Failed to initialize GLEW" << std::endl;
return -1;
}
// VAO, VBO
float vertices[] =
{
-0.5, -0.5, 0.0, // left
0.5, -0.5, 0.0, // right
0.0, 0.5, 0.0 // top
};
GLuint VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// Shaders
GLuint vertShader = compileShader("./vert.glsl", GL_VERTEX_SHADER);
GLuint fragShader = compileShader("./frag.glsl", GL_FRAGMENT_SHADER);
GLuint shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertShader);
glAttachShader(shaderProgram, fragShader);
glLinkProgram(shaderProgram);
GLint success;
GLchar infoLog[512];
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success)
{
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cerr << "shader linking failed" << std::endl
<< infoLog << std::endl;
}
// We no longer need the individual shaders
glDeleteShader(vertShader);
glDeleteShader(fragShader);
// Main loop
while (!glfwWindowShouldClose(window))
{
glClearColor(0.2, 0.3, 0.3, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
GLint timeLocation = glGetUniformLocation(shaderProgram, "_Time");
if (timeLocation == -1)
{
std::cerr << "Could not find uniform: _Time" << std::endl;
}
float timeValue = getTime();
glUniform1f(timeLocation, timeValue);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfwSwapBuffers(window);
glfwPollEvents();
}
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glfwTerminate();
return 0;
}