tsoding.bezier/cpu.c

#include "./common.h"

void render_line(SDL_Renderer *renderer,
                 Vec2 begin, Vec2 end,
                 uint32_t color)
{
    check_sdl_code(
        SDL_SetRenderDrawColor(renderer, HEX_COLOR(color)));

    check_sdl_code(
        SDL_RenderDrawLine(
            renderer,
            (int) floorf(begin.x),
            (int) floorf(begin.y),
            (int) floorf(end.x),
            (int) floorf(end.y)));
}

void fill_rect(SDL_Renderer *renderer, Vec2 pos, Vec2 size, uint32_t color)
{
    check_sdl_code(
        SDL_SetRenderDrawColor(renderer, HEX_COLOR(color)));

    const SDL_Rect rect = {
        (int) floorf(pos.x),
        (int) floorf(pos.y),
        (int) floorf(size.x),
        (int) floorf(size.y),
    };

    check_sdl_code(SDL_RenderFillRect(renderer, &rect));
}

void render_marker(SDL_Renderer *renderer, Vec2 pos, uint32_t color)
{
    const Vec2 size = vec2(MARKER_SIZE, MARKER_SIZE);
    fill_rect(
        renderer,
        vec2_sub(pos, vec2_scale(size, 0.5f)),
        size,
        color);
}

Vec2 beziern_sample(Vec2 *ps, Vec2 *xs, size_t n, float p)
{
    memcpy(xs, ps, sizeof(Vec2) * n);

    while (n > 1) {
        for (size_t i = 0; i < n - 1; ++i) {
            xs[i] = lerpv2(xs[i], xs[i + 1], p);
        }
        n -= 1;
    }

    return xs[0];
}

void render_bezier_markers(SDL_Renderer *renderer,
                           Vec2 *ps, Vec2 *xs, size_t n,
                           float s, uint32_t color)
{
    for (float p = 0.0f; p <= 1.0f; p += s) {
        render_marker(renderer, beziern_sample(ps, xs, n, p), color);
    }
}

void render_bezier_curve(SDL_Renderer *renderer,
                         Vec2 *ps, Vec2 *xs, size_t n,
                         float s, uint32_t color)
{
    for (float p = 0.0f; p <= 1.0f; p += s) {
        Vec2 begin = beziern_sample(ps, xs, n, p);
        Vec2 end = beziern_sample(ps, xs, n, p + s);
        render_line(renderer, begin, end, color);
    }
}

#define PS_CAPACITY 256

Vec2 ps[PS_CAPACITY];
Vec2 xs[PS_CAPACITY];
size_t ps_count = 0;
int ps_selected = -1;

int ps_at(Vec2 pos)
{
    const Vec2 ps_size = vec2(MARKER_SIZE, MARKER_SIZE);
    for (size_t i = 0; i < ps_count; ++i) {
        const Vec2 ps_begin = vec2_sub(ps[i], vec2_scale(ps_size, 0.5f));
        const Vec2 ps_end = vec2_add(ps_begin, ps_size);
        if (ps_begin.x <= pos.x && pos.x <= ps_end.x &&
            ps_begin.y <= pos.y && pos.y <= ps_end.y) {
            return (int) i;
        }
    }
    return -1;
}

int main(void)
{
    check_sdl_code(
        SDL_Init(SDL_INIT_VIDEO));

    SDL_Window * const window =
        check_sdl_ptr(
            SDL_CreateWindow(
                "Bezier Curves",
                0, 0,
                SCREEN_WIDTH,
                SCREEN_HEIGHT,
                SDL_WINDOW_RESIZABLE));

    SDL_Renderer * const renderer =
        check_sdl_ptr(
            SDL_CreateRenderer(
                window, -1, SDL_RENDERER_ACCELERATED));

    check_sdl_code(
        SDL_RenderSetLogicalSize(renderer, SCREEN_WIDTH, SCREEN_HEIGHT));

    int quit = 0;
    int markers = 1;
    float t = 0.0f;
    float bezier_sample_step = 0.05f;
    while (!quit) {
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            switch (event.type) {
            case SDL_QUIT:
                quit = 1;
                break;

            case SDL_KEYDOWN: {
                switch (event.key.keysym.sym) {
                case SDLK_F1: {
                    markers = !markers;
                } break;
                }
            } break;

            case SDL_MOUSEBUTTONDOWN: {
                switch (event.button.button) {
                case SDL_BUTTON_LEFT: {
                    const Vec2 mouse_pos = vec2(event.button.x, event.button.y);
                    ps_selected = ps_at(mouse_pos);

                    if (ps_selected < 0 && ps_count < PS_CAPACITY) {
                        ps[ps_count++] = mouse_pos;
                    }
                } break;
                }
            } break;

            case SDL_MOUSEBUTTONUP: {
                if (event.button.button == SDL_BUTTON_LEFT) {
                    ps_selected = -1;
                }
            } break;

            case SDL_MOUSEMOTION: {
                Vec2 mouse_pos = vec2(event.motion.x, event.motion.y);
                if (ps_selected >= 0) {
                    ps[ps_selected] = mouse_pos;
                }
            } break;

            case SDL_MOUSEWHEEL: {
                if (event.wheel.y > 0) {
                    bezier_sample_step = fminf(bezier_sample_step + 0.001f, 0.999f);
                } else if (event.wheel.y < 0) {
                    bezier_sample_step = fmaxf(bezier_sample_step - 0.001f, 0.001f);
                }
            } break;
            }
        }

        check_sdl_code(
            SDL_SetRenderDrawColor(
                renderer,
                HEX_COLOR(BACKGROUND_COLOR)));

        check_sdl_code(
            SDL_RenderClear(renderer));

        if (ps_count >= 1) {
            if (markers) {
                render_bezier_markers(
                    renderer,
                    ps, xs, ps_count,
                    bezier_sample_step,
                    GREEN_COLOR);
            } else {
                render_bezier_curve(
                    renderer,
                    ps, xs, ps_count,
                    bezier_sample_step,
                    GREEN_COLOR);
            }
        }

        for (size_t i = 0; i < ps_count; ++i) {
            render_marker(renderer, ps[i], RED_COLOR);
            if (i < ps_count - 1) {
                render_line(renderer, ps[i], ps[i + 1], RED_COLOR);
            }
        }

        SDL_RenderPresent(renderer);

        SDL_Delay(DELTA_TIME_MS);
        t += DELTA_TIME_SEC;
    }

    SDL_Quit();

    return 0;
}