driftwm/sim/render.py

from __future__ import annotations

import math
from pathlib import Path
from typing import Iterable

import numpy as np
from PIL import Image, ImageDraw

from driftwm.sim.boat import BoatSpec, get_boat_spec
from driftwm.sim.flow import Flow
from driftwm.sim.dynamics import rot_body_to_world
from driftwm.utils import ensure_dir


Color = tuple[int, int, int]


def _world_to_px(point: np.ndarray, workspace: tuple[float, float, float, float], size: int, pad: int) -> tuple[int, int]:
    xmin, xmax, ymin, ymax = workspace
    x = (point[0] - xmin) / max(1e-6, xmax - xmin)
    y = (point[1] - ymin) / max(1e-6, ymax - ymin)
    px = int(pad + x * (size - 2 * pad))
    py = int(size - pad - y * (size - 2 * pad))
    return px, py


def _draw_arrow(draw: ImageDraw.ImageDraw, p0: tuple[int, int], p1: tuple[int, int], color: Color, width: int = 2) -> None:
    draw.line([p0, p1], fill=color, width=width)
    dx = p1[0] - p0[0]
    dy = p1[1] - p0[1]
    angle = math.atan2(dy, dx)
    head = 8
    for sign in (-1, 1):
        a = angle + sign * 2.55
        p = (int(p1[0] + head * math.cos(a)), int(p1[1] + head * math.sin(a)))
        draw.line([p1, p], fill=color, width=width)


def draw_flow_field(
    draw: ImageDraw.ImageDraw,
    flow: Flow,
    workspace: tuple[float, float, float, float],
    size: int,
    pad: int,
    t: float = 0.0,
    grid: int = 9,
) -> None:
    xmin, xmax, ymin, ymax = workspace
    xs = np.linspace(xmin + 0.7, xmax - 0.7, grid)
    ys = np.linspace(ymin + 0.7, ymax - 0.7, grid)
    for x in xs:
        for y in ys:
            p = np.array([x, y], dtype=np.float32)
            v = flow.velocity(p, t)
            speed = float(np.linalg.norm(v))
            if speed < 1e-4:
                continue
            q = p + 0.75 * v / max(0.15, speed)
            p0 = _world_to_px(p, workspace, size, pad)
            p1 = _world_to_px(q, workspace, size, pad)
            _draw_arrow(draw, p0, p1, (160, 190, 218), width=1)


def draw_boat(
    draw: ImageDraw.ImageDraw,
    state: np.ndarray,
    spec: BoatSpec,
    workspace: tuple[float, float, float, float],
    size: int,
    pad: int,
    fill: Color = (38, 89, 133),
    outline: Color = (15, 37, 61),
) -> None:
    pos = state[:2]
    theta = float(state[2])
    rot = rot_body_to_world(theta)
    hull = (spec.hull_vertices @ rot.T) + pos
    pts = [_world_to_px(p, workspace, size, pad) for p in hull]
    draw.polygon(pts, fill=fill, outline=outline)
    nose = pos + rot @ np.array([0.56, 0.0], dtype=np.float32)
    _draw_arrow(draw, _world_to_px(pos, workspace, size, pad), _world_to_px(nose, workspace, size, pad), (230, 242, 255), width=2)
    for r, d in zip(spec.thruster_positions, spec.thruster_dirs):
        p = pos + rot @ r
        q = p + rot @ (r - 0.16 * d)
        _draw_arrow(draw, _world_to_px(q, workspace, size, pad), _world_to_px(p, workspace, size, pad), (215, 108, 71), width=2)


def render_frame(
    state: np.ndarray,
    boat: str | BoatSpec,
    flow: Flow,
    workspace: tuple[float, float, float, float] = (0.0, 10.0, 0.0, 10.0),
    trajectory: np.ndarray | None = None,
    goal: np.ndarray | None = None,
    planned: Iterable[np.ndarray] | None = None,
    size: int = 512,
    pad: int = 28,
    t: float = 0.0,
) -> Image.Image:
    spec = get_boat_spec(boat) if isinstance(boat, str) else boat
    img = Image.new("RGB", (size, size), (247, 250, 252))
    draw = ImageDraw.Draw(img, "RGBA")
    draw.rectangle([pad, pad, size - pad, size - pad], outline=(35, 54, 72, 255), width=2)
    draw_flow_field(draw, flow, workspace, size, pad, t=t)
    if planned is not None:
        for rollout in planned:
            pts = [_world_to_px(p[:2], workspace, size, pad) for p in rollout]
            if len(pts) > 1:
                draw.line(pts, fill=(110, 138, 183, 45), width=1)
    if trajectory is not None and len(trajectory) > 1:
        pts = [_world_to_px(p[:2], workspace, size, pad) for p in trajectory]
        draw.line(pts, fill=(22, 131, 105, 230), width=3)
    if goal is not None:
        gx, gy = _world_to_px(np.asarray(goal, dtype=np.float32), workspace, size, pad)
        r = 8
        draw.ellipse([gx - r, gy - r, gx + r, gy + r], fill=(211, 67, 78, 230), outline=(120, 25, 33, 255), width=2)
    draw_boat(draw, state, spec, workspace, size, pad)
    return img


def save_gif(frames: list[Image.Image], path: str | Path, duration_ms: int = 40) -> None:
    path = Path(path)
    ensure_dir(path.parent)
    if not frames:
        raise ValueError("no frames to save")
    frames[0].save(path, save_all=True, append_images=frames[1:], duration=duration_ms, loop=0)


def save_boat_geometry(boat: str, path: str | Path, size: int = 420) -> None:
    from driftwm.sim.flow import NoFlow

    state = np.array([5.0, 5.0, 0.0, 0.0, 0.0, 0.0], dtype=np.float32)
    img = render_frame(state, boat, NoFlow(), trajectory=None, size=size)
    path = Path(path)
    ensure_dir(path.parent)
    img.save(path)


def save_flow_quiver(flow: Flow, path: str | Path, workspace: tuple[float, float, float, float] = (0.0, 10.0, 0.0, 10.0)) -> None:
    state = np.array([5.0, 5.0, 0.0, 0.0, 0.0, 0.0], dtype=np.float32)
    img = render_frame(state, "twin", flow, workspace=workspace, trajectory=None)
    path = Path(path)
    ensure_dir(path.parent)
    img.save(path)