townengine/apps/examples/circle-raster/game.c

#include "twn_game_api.h"
#include "state.h"

#include <malloc.h>
#include <math.h>


/* Emits `x` and `y` for every intersecting cell */
/* We snap position to the nearest corner, which means there's no aliasing */
/* It works great for integer radii */
#define m_iter_circle_pixels(p_center_x, p_center_y, p_radius) \
    for (float y = (p_center_y + ceilf(p_radius)) - 1; y > (p_center_y - ceilf(p_radius)) - 1; --y) \
        for (float x = p_center_x - ceilf(sqrtf(p_radius * p_radius - (y - p_center_y + (y <= p_center_y)) * (y - p_center_y + (y <= p_center_y)))); x < p_center_x + ceilf(sqrtf(p_radius * p_radius - (y - p_center_y + (y <= p_center_y)) * (y - p_center_y + (y <= p_center_y)))); ++x)


static int32_t ceil_sqrt(int32_t const n) {
    int32_t res = 1;
    #pragma clang loop unroll_count(8)
    while(res * res < n)
        res++;
    return res;
}


static void benchmark(struct state *state) {
    volatile float x, y;

    profile_start("float");

    for (int i = 0; i < 1000; ++i) {
        float const rs = state->r * state->r;
        float const cr = ceilf(state->r);
        for (float iy = -cr; iy <= cr - 1; ++iy) {
            float const dx = ceilf(sqrtf(rs - (iy + (iy <= 0)) * (iy + (iy <= 0))));
            for (float ix = -dx; ix < dx; ++ix) {
                x = ix;
                y = iy;
            }
        }
    }

    profile_end("float");

    profile_start("int32_t");

    for (int i = 0; i < 1000; ++i) {
        int32_t const rsi = (int32_t)state->r * (int32_t)state->r;
        for (int32_t iy = -(int32_t)state->r; iy <= (int32_t)state->r - 1; ++iy) {
            int32_t const dx = ceil_sqrt(rsi - (iy + (iy <= 0)) * (iy + (iy <= 0)));
            for (int32_t ix = -dx; ix < dx; ++ix) {
                x = (float)ix;
                y = (float)iy;
            }
        }
    }

    profile_end("int32_t");

    profile_start("int32_t acc");

    for (int i = 0; i < 1000; ++i) {
        int32_t const rsi = (int32_t)state->r * (int32_t)state->r;
        int32_t acc = 1;
        for (int32_t iy = (int32_t)state->r - 1; iy >= 0; --iy) {
            while (acc * acc < rsi - iy * iy) acc++;
            for (int32_t ix = -acc; ix < acc; ++ix) {
                /* lower portion */
                x = (float)ix;
                y = (float)iy;
                /* upper portion */
                x = (float)ix;
                y = (float)-iy - 1;
            }
        }
    }

    profile_end("int32_t acc");

    (void)x; (void)y;
}


void game_tick(void) {
    if (ctx.initialization_needed) {
        if (!ctx.udata) {
            ctx.udata = ccalloc(1, sizeof (struct state));
            struct state *state = ctx.udata;
            state->r = 10;
        }
    }

    struct state *state = ctx.udata;

    Vec2 const mouse_snap = {floorf(ctx.mouse_position.x / 8) * 8, floorf(ctx.mouse_position.y / 8) * 8};

    input_action("up", CONTROL_LEFT_MOUSE);
    input_action("down", CONTROL_RIGHT_MOUSE);

    if (input_action_just_pressed("up"))
        state->r += 1;
    if (input_action_just_pressed("down"))
        state->r -= 1;

    int32_t const rsi = (int32_t)state->r * (int32_t)state->r;
    int32_t acc = 1;
    for (int32_t iy = (int32_t)state->r - 1; iy >= 0; --iy) {
        while (acc * acc < rsi - iy * iy) acc++;
        for (int32_t ix = -acc; ix < acc; ++ix) {
            /* lower portion */
            draw_box((Rect){mouse_snap.x + (float)ix * 8, mouse_snap.y + (float)iy * 8, 8, 8}, 1, (Color){125, 125, 0, 255});
            /* upper portion */
            draw_box((Rect){mouse_snap.x + (float)ix * 8, mouse_snap.y + (float)(-iy - 1) * 8, 8, 8}, 1, (Color){125, 125, 0, 255});
        }
    }

    draw_circle(mouse_snap, state->r * 8, (Color){125, 125, 125, 125});

    benchmark(state);
}


void game_end(void) {
    /* do your deinitialization here */
    struct state *state = ctx.udata;
    free(state);
}