python-objrender/main.py

#!/usr/bin/env python3

import argparse
import re
from math import cos, sin
from typing import cast
import dearpygui.dearpygui as dpg  # pyright: ignore[reportMissingTypeStubs]

RENDER_VERTICES = True
RENDER_EDGES = True
BEST_EFFORT_PARSE = True

CANVAS_SIZE = 500
TIMESTEP = 0.01
CAMERA_DISTANCE = 2.5

VERTEX_SIZE = 5.0
VERTEX_COLOR = (27, 188, 104)
EDGE_SIZE = 1.0
EDGE_COLOR = (20, 133, 38)

Vertex2 = tuple[float, float]
Vertex2Set = list[Vertex2]
Vertex3 = tuple[float, float, float]
Vertex3Set = list[Vertex3]
IndexedFace = tuple[int, int, int, int]
IndexedFaceSet = list[IndexedFace]


# 3D Space [-1, 1]x[-1, 1]x[-1, 1] -> 2D ImagePlane [-1, 1]x[-1, 1] -> Viewport in [0, WIDTH]x[0, HEIGHT]


def to_viewport(verts: Vertex2Set) -> Vertex2Set:
    """Maps vertices into the [0, WIDTH]x[0, HEIGHT] viewport"""

    def transform(vert: Vertex2) -> Vertex2:
        return (
            ((vert[0] + 1.0) / 2.0) * CANVAS_SIZE,
            (1 - (vert[1] + 1.0) / 2.0) * CANVAS_SIZE,
        )

    return list(map(transform, verts))


def to_imageplane(verts: Vertex3Set) -> Vertex2Set:
    """Projects vertices onto the [-1, 1]x[-1, 1] imageplane"""

    def transform(vert: Vertex3) -> Vertex2:
        return (vert[0] / vert[2], vert[1] / vert[2])

    return list(map(transform, verts))


def translate(verts: Vertex3Set, distance: float) -> Vertex3Set:
    """Translates vertices along the forward-axis in 3D space"""

    def transform(vert: Vertex3) -> Vertex3:
        return (vert[0], vert[1], vert[2] + distance)

    return list(map(transform, verts))


def rotate(verts: Vertex3Set, angle: float) -> Vertex3Set:
    """Rotates vertices around the up-axis in 3D space"""

    def transform(vert: Vertex3) -> Vertex3:
        return (
            vert[0] * cos(angle) - vert[2] * sin(angle),
            vert[1],
            vert[0] * sin(angle) + vert[2] * cos(angle),
        )

    return list(map(transform, verts))


def draw(drawlist, vertices: Vertex3Set, faces: IndexedFaceSet, time: float):
    dpg.delete_item(drawlist, children_only=True)

    def draw_vertex(vert: Vertex2) -> None:
        _ = dpg.draw_circle(
            center=(vert[0], vert[1]),
            radius=VERTEX_SIZE,
            parent=drawlist,
            fill=VERTEX_COLOR,
            color=VERTEX_COLOR,
        )

    def draw_line(vertA: Vertex2, vertB: Vertex2) -> None:
        _ = dpg.draw_line(
            p1=(vertA[0], vertA[1]),
            p2=(vertB[0], vertB[1]),
            parent=drawlist,
            color=EDGE_COLOR,
            thickness=EDGE_SIZE,
        )

    rotated_vertices: Vertex3Set = rotate(vertices, time)
    translated_vertices: Vertex3Set = translate(rotated_vertices, CAMERA_DISTANCE)
    imageplane_vertices: Vertex2Set = to_imageplane(translated_vertices)
    viewport_vertices: Vertex2Set = to_viewport(imageplane_vertices)

    if RENDER_VERTICES:
        for v in viewport_vertices:
            draw_vertex(v)

    if RENDER_EDGES:
        for f in faces:
            v0: Vertex2 = viewport_vertices[f[0]]
            v1: Vertex2 = viewport_vertices[f[1]]
            v2: Vertex2 = viewport_vertices[f[2]]
            v3: Vertex2 = viewport_vertices[f[3]]

            draw_line(v0, v1)
            draw_line(v1, v2)
            draw_line(v2, v3)
            draw_line(v3, v0)


def parse_obj_file(path: str) -> tuple[Vertex3Set, IndexedFaceSet]:
    with open(path, "r") as file:
        lines = file.readlines()

    vertices: Vertex3Set = []
    faces: IndexedFaceSet = []

    for line in lines:
        if line.startswith("v "):

            matches = re.findall(r"^v (.*?) (.*?) (.*?)$", line)
            if len(matches) != 1:
                if BEST_EFFORT_PARSE:
                    continue
                raise RuntimeError("Failed to parse .obj file")

            x, y, z = matches[0]
            vertices += [(float(x), float(y), float(z))]

        elif line.startswith("f "):

            matches = re.findall(r"^f (.*?) (.*?) (.*?) (.*?)$", line)
            if len(matches) != 1:
                if BEST_EFFORT_PARSE:
                    continue
                raise RuntimeError("Failed to parse .obj file")

            v0, v1, v2, v3 = matches[0]
            v0 = int(v0) - 1
            v1 = int(v1) - 1
            v2 = int(v2) - 1
            v3 = int(v3) - 1
            faces += [(v0, v1, v2, v3)]

    return vertices, faces


def main():
    parser = argparse.ArgumentParser()
    _ = parser.add_argument("objfile", type=str, help=".obj file to render")
    _ = parser.add_argument("--vertices", action="store_true", help="render vertices")
    _ = parser.add_argument("--edges", action="store_true", help="render edges")
    _ = parser.add_argument(
        "--strict", action="store_true", help="require complete parsing of .obj file"
    )
    args = parser.parse_args()
    args.objfile = cast(str, args.objfile)

    global RENDER_VERTICES
    global RENDER_EDGES
    global BEST_EFFORT_PARSE

    RENDER_VERTICES = bool(args.vertices)
    RENDER_EDGES = bool(args.edges)
    BEST_EFFORT_PARSE = not bool(args.strict)

    dpg.create_context()

    with dpg.theme() as canvas_theme, dpg.theme_component():
        _ = dpg.add_theme_style(dpg.mvStyleVar_WindowPadding, 0, 0)

    with dpg.window(label="Obj Render") as canvas:
        dpg.bind_item_theme(canvas, canvas_theme)
        dpg.set_primary_window(dpg.last_item(), True)

        with dpg.drawlist(width=CANVAS_SIZE, height=CANVAS_SIZE) as d:
            drawlist = d

    dpg.create_viewport(title="Obj Render", width=CANVAS_SIZE, height=CANVAS_SIZE)
    dpg.setup_dearpygui()
    dpg.show_viewport()

    vertices, faces = parse_obj_file(args.objfile)

    time: float = 0
    while dpg.is_dearpygui_running():
        draw(drawlist, vertices, faces, time)
        dpg.render_dearpygui_frame()
        time += TIMESTEP

    dpg.destroy_context()


if __name__ == "__main__":
    main()