implement obj rendering

main.py

@@ -0,0 +1,181 @@
+#!/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 = False
+RENDER_EDGES = True
+BEST_EFFORT_PARSE = True
+
+CANVAS_SIZE = 500
+TIMESTEP = 0.01
+CAMERA_DISTANCE = 3.0
+
+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:
+    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:
+    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:
+    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:
+    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,
+        )
+
+    viewport_vertices: Vertex2Set = to_viewport(
+        to_imageplane(translate(rotate(vertices, time), CAMERA_DISTANCE))
+    )
+
+    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")
+    args = parser.parse_args()
+    args.objfile = cast(str, args.objfile)
+
+    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()