skein/src/hello.cpp

// 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 run in VSCode
// https://code.visualstudio.com/docs/cpp/config-mingw

// To compile on Arch Linux
//
// Install dependencies
// sudo pacman -S glfw mesa glew
//
// Build
// cmake ..
// cmake --build .

#include "glm/glm.hpp"
#include "glm/gtc/matrix_transform.hpp"
#include <GL/glew.h>
#include <GLFW/glfw3.h>

#include <iostream>
#include <string>

#include "gfx.hpp"
#include "icosphere.hpp"
#include "orbit.hpp"

#include <cmath>
#include "astro/twoBodyMethods.hpp"

const int WIDTH = 640;
const int HEIGHT = 480;
const float ASPECT = (float)WIDTH / (float)HEIGHT;

// Initialize GLFW, OpenGL and GLEW, open a window and make it the current context.
// Returns 0 for success, and -1 for any failure.
// Failures are printed to STDERR.
int initGraphics(GLFWwindow** window)
{
    // Set up GLFW, OpenGL and GLEW.
    if (!glfwInit())
    {
        std::cerr << "Failed to initialize GLFW" << std::endl;
        return -1;
    }
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    *window = glfwCreateWindow(WIDTH, HEIGHT, "Hello Astro", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        std::cerr << "Failed to open window with GLFW" << std::endl;
        return -1;
    }

    glfwMakeContextCurrent(*window);

    glewExperimental = GL_TRUE;
    if (glewInit() != GLEW_OK)
    {
        std::cerr << "Failed to initialize GLEW" << std::endl;
        return -1;
    }

    glEnable(GL_DEPTH_TEST);

    return 0;
}

GLint getShaderUniformLocation(GLuint shaderProgram, const std::string& uniformName)
{
    GLint location = glGetUniformLocation(shaderProgram, uniformName.c_str());
    if (location == -1)
    {
        std::cerr << "Could not find uniform: " << uniformName << std::endl;
        return -1;
    }

    return location;
}

void updateProjectionMatrix(GLuint shaderProgram)
{
    float left = -ASPECT, right = ASPECT, bottom = -1.0, top = 1.0, near = -1.0, far = 1.0;
    glm::mat4 projection = glm::ortho(left, right, bottom, top, near, far);
    GLint projectionLocation = getShaderUniformLocation(shaderProgram, "_Projection");
    glUniformMatrix4fv(projectionLocation, 1, GL_FALSE, &projection[0][0]);
}

void updateModelMatrix(GLuint shaderProgram, float time)
{
    constexpr float angle = glm::radians(10.0);
    glm::vec3 axis = glm::vec3(0.0, 1.0, 0.0);
    glm::mat4 model = glm::rotate(glm::mat4(1.0), angle * time, axis);
    GLint modelLocation = getShaderUniformLocation(shaderProgram, "_Model");
    glUniformMatrix4fv(modelLocation, 1, GL_FALSE, &model[0][0]);
}

void updateViewMatrix(GLuint shaderProgram)
{
    glm::mat4 view = glm::mat4(1.0);
    GLint viewLocation = getShaderUniformLocation(shaderProgram, "_View");
    glUniformMatrix4fv(viewLocation, 1, GL_FALSE, &view[0][0]);
}

void updateModelViewProjectionMatrix(GLuint shaderProgram, float time)
{
    // Calculate matrices
    updateProjectionMatrix(shaderProgram);
    updateModelMatrix(shaderProgram, time);
    updateViewMatrix(shaderProgram);
}

int main()
{
    // Calculate period of ISS orbit around the Earth
    const float semiMajorAxis = 6738000;
    const float gravitationalParameter = 3.986e14;
    float period = astro::computeKeplerOrbitalPeriod(semiMajorAxis, gravitationalParameter);
    period /= 60.0;
    std::cout << period << std::endl;

    glm::vec3 v(0.0, 1.0, 2.0);
    std::cout << "(" << v.x << ", " << v.y << ", " << v.z << ")" << std::endl;

    GLFWwindow* window = nullptr;
    if (initGraphics(&window) != 0)
        return -1;

    GLuint litProgram = compileShaderProgram("./frag_lit.glsl");
    GLuint unlitProgram = compileShaderProgram("./frag_unlit.glsl");

    Icosphere sphere(0.5, 2);
    Orbit orbit(30, glm::vec3(.5, .5, 0));

    // Main loop
    while (!glfwWindowShouldClose(window))
    {
        glClearColor(0.2, 0.3, 0.3, 1.0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        float time = glfwGetTime();

        // Render lit objects
        glUseProgram(litProgram);
        updateModelViewProjectionMatrix(litProgram, time);
        sphere.render();

        // Render unlit objects
        glUseProgram(unlitProgram);
        updateModelViewProjectionMatrix(unlitProgram, time);
        orbit.render();

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}