TheGrandVisualizerShow/effect_starfield.c

//Standard lib
#include <stdio.h>

//Third party
#include "raylib.h"

//Our own files
#include "constants.h"
#include "programstate.h"
#include "effect_starfield.h"

extern ProgramState programState;
static int screenWidth;
static int screenHeight;
static const int numberOfStars=540;

static const int starLayers = 3;

typedef struct {
    int x;
    int y;
    int z;
    Color color;
    float rand;
} Star;

static Star stars[540]; //1080 * 0.5   Not quite one star per line

void reposition() {
    //Recreate all stars and begin from blank.
    //We want a certain star density, no matter the screen resolution

    screenWidth = GetScreenWidth();
    screenHeight = GetScreenHeight();
    Color color;
    int rand;
    int layer;
    int partitionSize=(starLayers+1)*2 / 8; //8 partions
    for (int i=0; i<numberOfStars; i++) {
        rand = GetRandomValue(1, (starLayers+1)*2);
        if (rand<= 5*partitionSize) layer = 1;
        else if (rand<= 7*partitionSize) layer = 2;
        else if (rand<= 8*partitionSize) layer = 3;

        switch (layer) {
            //0 does not exist
            case 1:
                color = BROWN;
                break;
            case 2:
                color = BEIGE;
                break;
            case 3:
                color = PURPLE;
                break;
            default:
                color = DARKBLUE;
        }


        float randomFactor =  ((float)GetRandomValue(0, 20)-10.0f) / 100.0f;
        stars[i] = (Star){ GetRandomValue(0, screenWidth), GetRandomValue(0, screenHeight), layer, color, randomFactor };
    }
}

void effect_starfield(bool redrawNeeded, float opacity, int speedModifier, int size) {

    float ft = GetFrameTime();
    int bpmFactor = programState.bpm/40 * programState.bpm/20; //exponential curve. The higher bpm the faster we get. Below 90 it should feel really slow
    Star * star;

    if (redrawNeeded) {
        reposition();
    }

    for (int i=0; i<numberOfStars; i++) {
        star = &stars[i];

        if (programState.transportRolling) {
            //Move Forward
            star->x -= (star->z * ft * bpmFactor * 3 * speedModifier); //... the mysterious number 3.
            //wrap around
            if (star->x <= 0) {
                star->x += screenWidth;
                star->y = GetRandomValue(0, screenHeight);
            }
            else if (star->x > screenWidth) {
                star->x -= screenWidth;
                star->y = GetRandomValue(0, screenHeight);
            }
        }

        //Wobble wobble
        int rand = GetRandomValue(1, 200);
        if (rand == 1) {star->y += 1;}
        else if (rand == 2) {star->y -= 1;}

        DrawRectangle(star->x, star->y, size, size, Fade(star->color, opacity));
    }
}