skein/src/main.cpp

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

#include "gfx.hpp"
#include "icosphere.hpp"
#include "particlevisualizer.hpp"
#include "orbitvisualizer.hpp"
#include "widget.hpp"

#include <skein/orbit.h>
#include <skein/particle.h>
#include <skein/particlemap.h>

#include <chrono>

// INPUT!
//
// what input do we even want in the first place?
// * camera controls - this is a rendering only concern which needn't affect the orbital
// * model validation - we want to modify orbits over time to confirm that our model is
// working properly
//
// TODO: input can only be directly handled by static methods, so we need to find a way to collect
// input from object instances and handle it at a higher level. in the case of this class, we want
// to determine when a configurable key is pressed. alternatively, we can split the behaviour into
// multiple sub-classes and run different loops at the top level?
//
// another idea is to process all input into a well-defined Input struct in the main loop, then
// pass this struct into objects' render() method.
//
// it's possible the first idea makes the most sense if the plan is to ultimately extract the orbit
// stuff to a library, since it keeps input a separate concern from the physics model
struct Input
{
    bool pauseTime;
    bool printCartesian;
} input;


void keyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
    if (action == GLFW_PRESS)
    {
        input.pauseTime = key == GLFW_KEY_SPACE;
        input.printCartesian = key == GLFW_KEY_W;
    }
}

void clearInput()
{
    input.pauseTime = false;
    input.printCartesian = false;
}

// now should always increase linearly with real world time, this should not be modified by input
// for animations etc
struct Time
{
    double now;
    double dt;
} engineTime;

void updateTime()
{
    std::chrono::duration timeSinceEpoch = std::chrono::steady_clock::now().time_since_epoch();
    double now = std::chrono::duration<double>(timeSinceEpoch).count();
    double dt = now - engineTime.now;

    engineTime.dt = dt;
    engineTime.now = now;
}

void printVector(const glm::dvec3& vector)
{
    std::cout << "(" << vector.x << ", " << vector.y << ", " << vector.z << ")";
}

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

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

    // set parameters of moon's orbit around earth
    Orbit moonOrbit;
    double moonOrbitSemiMajorAxis =  3.84748e8;
    moonOrbit.setSemiMajorAxis(moonOrbitSemiMajorAxis); // metres
    moonOrbit.setEccentricity(0.055);
    moonOrbit.setInclination(glm::radians(5.15));       // radians
    moonOrbit.setArgumentOfPeriapsis(318.15);           // in the case of the moon these last two values are
    moonOrbit.setLongitudeOfAscendingNode(60.0);        // pretty much constantly changing so use whatever

    // set parameters of satellite orbit around moon
    Orbit stationOrbit;
    stationOrbit.setSemiMajorAxis(5e7);
    stationOrbit.setEccentricity(0.6);
    stationOrbit.setInclination(glm::radians(89.0));
    stationOrbit.setArgumentOfPeriapsis(43.2);
    stationOrbit.setLongitudeOfAscendingNode(239.7);

    ParticleMap map;
    map.setParticle({"earth", 5.9e24});
    map.setParticle({"moon", 7.3e22});
    map.setParticle({"station", 1e6});
    map.setRelationship("earth", "moon", moonOrbit);
    map.setRelationship("moon", "station", stationOrbit);

    float scale = moonOrbitSemiMajorAxis * 1.1;
    ParticleVisualizer earthVis(map, "earth", 0.1, litProgram, unlitProgram, scale);
    ParticleVisualizer moonVis(map, "moon", 0.02, litProgram, unlitProgram, scale);
    ParticleVisualizer stationVis(map, "station", 0.01, litProgram, unlitProgram, scale);
    OrbitVisualizer moonOrbitVis(map, "moon", unlitProgram, scale);
    OrbitVisualizer stationOrbitVis(map, "station", unlitProgram, scale);

    // register input
    glfwSetKeyCallback(window, keyCallback);

    // TODO: convert these to an enum
    const int MODE_ORBIT     = 0;
    const int MODE_MANEOUVRE = 1;
    int mode = 0;

    // simulation time. this can be paused or whatever as animation demands.
    double time = 0;

    // Main loop
    while (!glfwWindowShouldClose(window))
    {
        // receive input - key callback populates input struct defined further up,
        // clearInput() needs to be called to clear input from previous frame
        clearInput();
        glfwPollEvents();
        updateTime();

        // apply input
        if (input.pauseTime)
        {
            mode++;
            if (mode > MODE_MANEOUVRE)
            {
                mode = 0;
            }
        }

        // the moon takes like 27 days to orbit earth. to see this in motion, then, we need to
        // increase the speed of time by 60 * 60 * 24 to see 1 day per second.
        const double speed = 60 * 60 * 24;

        // orbit modifications need to be instanteneous
        if (mode == MODE_ORBIT)
        {
            time += engineTime.dt * speed;
        }
        else
        {
            if (input.printCartesian)
            {

                const glm::dvec3 p = map.getParticleLocalPosition("station", time);
                printVector(p);
                std::cout << std::endl;

                // TODO: what unit is this in lol
                const glm::dvec3 v = map.getParticleLocalVelocity("station", time);
                const glm::dvec3 newVelocity = v * 0.9;

                printVector(v);
                std::cout << " -> ";
                printVector(newVelocity);
                std::cout << std::endl;

                map.setParticleLocalVelocity("station", time, newVelocity);
            }
        }

        // rendering
        glClearColor(0.2, 0.3, 0.3, 1.0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        earthVis.render(time);
        moonVis.render(time);
        stationVis.render(time);
        moonOrbitVis.render(time);
        stationOrbitVis.render(time);

        glfwSwapBuffers(window);
    }

    glfwTerminate();
    return 0;
}