becs/examples/example1/example1.c

#define BECS_MAX_ENTITIES 100000
#define BECS_MAX_COMPONENTS 4
#define BECS_IMPLEMENTATION
#include "../../becs.h"
#include <stdlib.h>
#include <stdio.h>
#include "external/raylib/src/raylib.h"

// Component structs
typedef struct {
    float x, y;
} Position;

typedef struct {
    float vx, vy;
} Velocity;

typedef struct {
    float ax, ay;
} Acceleration;

typedef struct {
    float radius;
    float lifetime;
} ParticleData;

// Function to spawn a particle
void SpawnParticle(BECS_ECS *ecs, BECS_ComponentID posID, BECS_ComponentID velID, BECS_ComponentID accID, BECS_ComponentID dataID, float x, float y) {
    BECS_Entity entity = BECS_EntityCreate(ecs);
    if (entity == BECS_NULL_ENTITY) return;

    Position *pos = (Position *)BECS_ComponentAdd(ecs, entity, posID);
    pos->x = x;
    pos->y = y;

    Velocity *vel = (Velocity *)BECS_ComponentAdd(ecs, entity, velID);
    vel->vx = GetRandomValue(-100, 100);
    vel->vy = GetRandomValue(-200, -50);

    Acceleration *acc = (Acceleration *)BECS_ComponentAdd(ecs, entity, accID);
    acc->ax = 0.0f;
    acc->ay = 100.0f; // Gravity

    ParticleData *data = (ParticleData *)BECS_ComponentAdd(ecs, entity, dataID);
    data->radius = 5.0f;
    data->lifetime = 2.0f;
}

void LifetimeSystem(BECS_ECS *ecs, float dt) {
    ParticleData *data = (ParticleData *)ecs->componentPools[3].denseArray;
    BECS_Entity *entity = (BECS_Entity *)ecs->componentPools[3].denseEntityMapping;
    for (uint32_t i = 0; i < ecs->entityCount; i++) {
        data[i].lifetime -= dt;
        if (data[i].lifetime <= 0.0f) {
            BECS_EntityDestroy(ecs, entity[i]);
        }
    }
}

void PhysicsSystem(BECS_ECS *ecs, float dt) {
    Position *pos = ((Position *)ecs->componentPools[0].denseArray);
    Velocity *vel = ((Velocity *)ecs->componentPools[1].denseArray);
    Acceleration *acc = ((Acceleration *)ecs->componentPools[2].denseArray);
    for (uint32_t i = 0; i < ecs->entityCount; i++)
    {
        vel[i].vy += acc[i].ay * dt;
        vel[i].vx += acc[i].ax * dt;
        pos[i].y += vel[i].vy * dt;
        pos[i].x += vel[i].vx * dt;
    }
}

void RenderSystem(BECS_ECS *ecs, float dt) {
    Position *pos = ((Position *)ecs->componentPools[0].denseArray);
    ParticleData *data = ((ParticleData *)ecs->componentPools[3].denseArray);
    for (uint32_t i = 0; i < ecs->entityCount; i++)
    {
        float alpha = data[i].lifetime / 2.0;
        Color color = {255, 255, 255, (unsigned char)(alpha * 255)};
        DrawCircle(pos[i].x, pos[i].y, data[i].radius, color);
    }
}

int main(void) {
    // Initialize ECS
    size_t componentSizes[4] = {sizeof(Position), sizeof(Velocity), sizeof(Acceleration), sizeof(ParticleData)};
    size_t memSize = BECS_GetMinMemoryArenaSize(componentSizes, 4);
    printf("%lu\n", memSize);
    char *memory = (char *)malloc(memSize);
    BECS_ECS ecs = BECS_InitECS(memory, memSize);

    // Register components
    BECS_ComponentID posID = BECS_ComponentRegister(&ecs, sizeof(Position), BECS_MAX_ENTITIES);
    BECS_ComponentID velID = BECS_ComponentRegister(&ecs, sizeof(Velocity), BECS_MAX_ENTITIES);
    BECS_ComponentID accID = BECS_ComponentRegister(&ecs, sizeof(Acceleration), BECS_MAX_ENTITIES);
    BECS_ComponentID dataID = BECS_ComponentRegister(&ecs, sizeof(ParticleData), BECS_MAX_ENTITIES);

    InitWindow(1600, 800, "2D Particle System with BECS");

    while (!WindowShouldClose()) {
        float dt = GetFrameTime();

        // Update lifetimes and despawn
        // for (BECS_Entity entity = 0; entity < BECS_MAX_ENTITIES; entity++) {
        //     if (!BECS_IsEntityAlive(&ecs, entity)) continue;
        //     if (BECS_ComponentHas(&ecs, entity, dataID)) {
        //         ParticleData *data = (ParticleData *)BECS_ComponentGet(&ecs, entity, dataID);
        //         data->lifetime -= dt;
        //         if (data->lifetime <= 0.0f) {
        //             BECS_EntityDestroy(&ecs, entity);
        //         }
        //     }
        // }
        LifetimeSystem(&ecs, dt);

        // Spawn particle on mouse click
        if (IsMouseButtonDown(MOUSE_LEFT_BUTTON)) {
            Vector2 mousePos = GetMousePosition();
            for (uint32_t i = 0; i < 10000; i++) {
                SpawnParticle(&ecs, posID, velID, accID, dataID, mousePos.x, mousePos.y);
            }
        }

        // Physics system: update position and velocity
        // for (BECS_Entity entity = 0; entity < BECS_MAX_ENTITIES; entity++) {
        //     if (!BECS_IsEntityAlive(&ecs, entity)) continue;
        //     if (BECS_ComponentHas(&ecs, entity, posID) &&
        //         BECS_ComponentHas(&ecs, entity, velID) &&
        //         BECS_ComponentHas(&ecs, entity, accID)) {
        //         Position *pos = (Position *)BECS_ComponentGet(&ecs, entity, posID);
        //         Velocity *vel = (Velocity *)BECS_ComponentGet(&ecs, entity, velID);
        //         Acceleration *acc = (Acceleration *)BECS_ComponentGet(&ecs, entity, accID);
        //
        //         vel->vx += acc->ax * dt;
        //         vel->vy += acc->ay * dt;
        //         pos->x += vel->vx * dt;
        //         pos->y += vel->vy * dt;
        //     }
        // }

        PhysicsSystem(&ecs, dt);

        BeginDrawing();
            ClearBackground(BLACK);

            // Render system: draw particles
            // for (BECS_Entity entity = 0; entity < BECS_MAX_ENTITIES; entity++) {
            //     if (!BECS_IsEntityAlive(&ecs, entity)) continue;
            //     if (BECS_ComponentHas(&ecs, entity, posID) && BECS_ComponentHas(&ecs, entity, dataID)) {
            //         Position *pos = (Position *)BECS_ComponentGet(&ecs, entity, posID);
            //         ParticleData *data = (ParticleData *)BECS_ComponentGet(&ecs, entity, dataID);
            //         float alpha = data->lifetime / 2.0f;
            //         Color color = {255, 255, 255, (unsigned char)(alpha * 255)};
            //         DrawCircle((int)pos->x, (int)pos->y, data->radius, color);
            //     }
            // }

            RenderSystem(&ecs, dt);

            DrawText(TextFormat("Particles: %u", ecs.entityCount), 10, 10, 20, WHITE);
        EndDrawing();
    }

    CloseWindow();
    free(memory);
    return 0;
}