Node tree text demo

3D cubes with text textures + 2D text overlay + Japanese text.

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Tags: 3d

Validates:

• Node tree → SceneAdapter → Renderer pipeline

• Camera3D view/projection matrices (row-major, Y-flipped)

• MeshInstance3D model_matrix with quaternion rotation

• Text2D overlay bridged to MSDF text renderer

• Lazy glyph loading for Japanese characters

• Text-as-texture on 3D geometry via Engine.create_text_texture()

Controls: ESC: Quit

Run with: uv run python examples/features/3d/text.py

Source

#!/usr/bin/env python3
"""Node tree text demo: 3D cubes with text textures + 2D text overlay + Japanese text.

Validates:
  - Node tree → SceneAdapter → Renderer pipeline
  - Camera3D view/projection matrices (row-major, Y-flipped)
  - MeshInstance3D model_matrix with quaternion rotation
  - Text2D overlay bridged to MSDF text renderer
  - Lazy glyph loading for Japanese characters
  - Text-as-texture on 3D geometry via Engine.create_text_texture()

Controls:
    ESC: Quit

Run with:
    uv run python examples/features/3d/text.py
"""

import math

from simvx.core import (
    Camera3D,
    DirectionalLight3D,
    Input,
    InputMap,
    Key,
    Material,
    Mesh,
    MeshInstance3D,
    Node,
    Text2D,
    Vec3,
)
from simvx.graphics import App


class RotatingCube(MeshInstance3D):
    """A cube that rotates around its Y axis."""

    def __init__(self, speed: float = 45.0, **kwargs):
        super().__init__(**kwargs)
        self.speed = speed

    def on_process(self, dt: float):
        self.rotate_y(math.radians(self.speed) * dt)


class TextDemoScene(Node):
    """Main demo scene with labeled cubes and text overlays."""

    def on_ready(self):
        InputMap.add_action("escape", [Key.ESCAPE])

        engine = self.app.engine

        # Camera: positioned to see cubes at origin
        camera = self.add_child(
            Camera3D(
                name="Camera",
                position=Vec3(0, 3, 8),
            )
        )
        camera.look_at(Vec3(0, 0, 0))
        camera.fov = 50.0

        light = self.add_child(DirectionalLight3D(name="Sun"))
        light.look_at(Vec3(-1, -2, -1))

        # Create text textures for each cube label
        labels = [
            ("RED", (1.0, 0.3, 0.3, 1.0)),
            ("GREEN", (0.3, 1.0, 0.4, 1.0)),
            ("BLUE", (0.4, 0.5, 1.0, 1.0)),
        ]
        text_textures = []
        for label, colour in labels:
            tt = engine.create_text_texture(size=48, width=256, height=64)
            tt.colour = colour
            tt.text = label
            text_textures.append(tt)

        # Red cube: left, rotating slowly
        red = self.add_child(
            RotatingCube(
                name="RedCube",
                position=Vec3(-2.5, 0, 0),
                speed=30.0,
            )
        )
        red.mesh = Mesh.cube(size=1.5)
        red.material = Material(colour=(0.9, 0.2, 0.2, 1.0))
        red.material.albedo_tex_index = text_textures[0].texture_index

        # Green cube: center, rotating faster
        green = self.add_child(
            RotatingCube(
                name="GreenCube",
                position=Vec3(0, 0, 0),
                speed=60.0,
            )
        )
        green.mesh = Mesh.cube(size=1.5)
        green.material = Material(colour=(0.2, 0.8, 0.3, 1.0))
        green.material.albedo_tex_index = text_textures[1].texture_index

        # Blue cube: right, counter-rotating
        blue = self.add_child(
            RotatingCube(
                name="BlueCube",
                position=Vec3(2.5, 0, 0),
                speed=-45.0,
            )
        )
        blue.mesh = Mesh.cube(size=1.5)
        blue.material = Material(colour=(0.2, 0.4, 0.9, 1.0))
        blue.material.albedo_tex_index = text_textures[2].texture_index

        # --- 2D text overlays ---
        self.add_child(
            Text2D(
                name="Title",
                text="SimVX Node Tree Demo",
                x=10.0,
                y=10.0,
                font_scale=2.0,
                colour=(1.0, 1.0, 1.0, 1.0),
            )
        )

        self.add_child(
            Text2D(
                name="Subtitle",
                text="3 rotating cubes with text textures + MSDF overlay",
                x=10.0,
                y=50.0,
                font_scale=1.2,
                colour=(0.71, 0.71, 0.71, 1.0),
            )
        )

        self.add_child(
            Text2D(name="Hiragana", text="ひらがな: あいうえお かきくけこ",
                   x=10.0, y=90.0, font_scale=1.2, colour=(1.0, 0.59, 0.78, 1.0))
        )
        self.add_child(
            Text2D(name="Katakana", text="カタカナ: アイウエオ カキクケコ",
                   x=10.0, y=120.0, font_scale=1.2, colour=(0.59, 0.78, 1.0, 1.0))
        )
        self.add_child(
            Text2D(name="Kanji", text="漢字: 東京都 日本語テスト",
                   x=10.0, y=150.0, font_scale=1.2, colour=(1.0, 0.9, 0.39, 1.0))
        )

        # Dynamic frame counter
        self.frame_text = self.add_child(
            Text2D(
                name="FrameCounter",
                text="Frame: 0",
                x=10.0,
                y=190.0,
                font_scale=1.0,
                colour=(0.39, 1.0, 0.39, 1.0),
            )
        )

        self.frame = 0

    def on_process(self, dt: float):
        self.frame += 1
        self.frame_text.text = f"Frame: {self.frame}  dt: {dt*1000:.1f}ms"

        if Input.is_action_just_pressed("escape"):
            self.app.quit()


def main():
    app = App(
        title="SimVX Node Tree + Text Demo",
        width=1280,
        height=720,
    )
    app.run(TextDemoScene())


if __name__ == "__main__":
    main()