skein/src/main.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 <GL/glew.h>
#include <GLFW/glfw3.h>
#include <astro/stateVectorIndices.hpp>

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

int main()
{
    GLFWwindow* window = nullptr;
    if (initGraphics(&window, "Hello Astro") != 0)
        return -1;

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

    Icosphere planet(0.2, 3, litProgram);
    Icosphere orbiter(0.07, 2, litProgram);

    std::vector<float> keplerianElements(6);
    keplerianElements[astro::semiMajorAxisIndex] = .75;
    keplerianElements[astro::eccentricityIndex] = .5;
    keplerianElements[astro::inclinationIndex] = 3.142 / 2.0 + 1;
    keplerianElements[astro::argumentOfPeriapsisIndex] = 2.0;
    keplerianElements[astro::longitudeOfAscendingNodeIndex] = 0;
    Orbit orbit(keplerianElements);

    Widget widget(orbit, unlitProgram);

    // 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();
        const float orbitalPeriod = 6.284;

        const int ANIM_ORBITING = 0;
        const int ANIM_ECCENTRICITY = 1;
        int animation = (int)(time / orbitalPeriod) % 2 == 1;

        glm::vec3 pos;
        if (animation == ANIM_ORBITING)
        {
            pos = orbit.getPosition(time);
        }
        else if (animation == ANIM_ECCENTRICITY)
        {
            float e = .25 + .2 * sin(time);
            keplerianElements[astro::eccentricityIndex] = e;
            orbit.setElements(keplerianElements);

            pos = orbit.getPosition(0);
        }
        orbiter.setPosition(pos);

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

        planet.render();
        orbiter.render();

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

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}