plutonium_engine

A pure Rust 2D graphics engine built on wgpu. SVG-first, DPI-aware, with text and optional widgets.

Features:

• SVG textures rendered via resvg/tiny-skia
• Texture atlases with per-tile UVs
• Text rendering via a font atlas
• Optional retained-mode widgets: Texture2D, TextureAtlas2D, Text2D, Button, TextInput (feature: widgets)
• Camera with boundary and tether
• Tweening helpers (feature: anim): Tween, Track::{Sequence,Parallel}, Timeline with labels/callbacks and CSS-like cubic-bezier easing
• Deterministic RNG streams and basic record/replay plumbing (feature: replay)

Coordinate system:

• Logical pixels; origin top-left, +x right, +y down. DPI scaling handled internally.

API styles:

• Immediate-mode: begin_frame(), draw_*, end_frame()
• Optional retained widgets (feature widgets): higher-level objects that render via the same draw path
• DrawParams supports z, scale, rotation, and tint (RGBA) for sprites

Cargo features:

[features]
default = ["backend-wgpu"]
backend-wgpu = []           # WGPU backend
raster = []                 # PNG/JPEG helpers
widgets = []                # Retained-mode widgets
layout = []                 # Simple layout helpers (anchors/percent)
anim = []                   # Tweening/animation helpers
replay = []                 # RNG streams and record/replay helpers

Versioning:

• The public API may evolve; see CHANGELOG.md for details.

Testing and CI:

• Unit tests (math, transforms, UVs) and headless snapshots (checkerboard, atlas, sprite, many sprites) are provided.
• Snapshots are intended to run locally; keep large perf snapshots out of CI.

Runtime and stepping:

• PlutoniumApp exposes set_fixed_timestep(dt_seconds) to run a fixed-dt update loop (useful for deterministic sims/tests).

CLI flags:

• App (run_app-based examples):
  • --record <path>: record per-frame inputs to JSON at <path>.
  • --replay <path>: replay inputs from <path>.
  • --dt <seconds>: set fixed timestep for the update loop.
  • --fps <hz>: alternative to --dt; sets fixed timestep to 1/fps.
• Snapshot runner (cargo run --bin snapshots):
  • --seed <u64>: seed for RNG-driven snapshots.
  • --record <path>: write a minimal script (--frames frames) to <path>.
  • --replay <path>: load the script at <path> and render a verification scene.
  • --frames <n>: number of frames for multiframe/timeline snapshots (default 3).
  • --dt <seconds>: per-frame delta for multiframe/timeline snapshots (default 0.2).
  • Set UPDATE_SNAPSHOTS=1 to update golden images on mismatch.

Further docs in docs/:

• docs/coordinates-and-dpi.md
• docs/api-styles.md
• docs/features-and-modules.md
• docs/layering.md
• docs/getting-started.md
• docs/layout.md
• docs/instancing-and-batching.md

Examples:

• actions_demo: input action map (buttons/axes) and button hover/press/focus visuals.

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