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Jérôme Bousquié
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# Effects: HDR, Post-process & Showcase
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Examples covering **HDR / tone mapping** and **post-process effects**, plus
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the full showcase that combines everything.
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| Example | Run command | What it shows |
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|---------|-------------|---------------|
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| `demo` | `cargo run -p wsg-lib --example demo` | **Full showcase**: 6 LOD primitives, 3 lights, shadows, HDR/ACES, bloom, culling, orbital camera |
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| `bloom` | `cargo run -p wsg-lib --example bloom` | Post-process bloom (glow around bright areas) |
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| `hdr` | `cargo run -p wsg-lib --example hdr` | HDR + tone mapping (ACES) + runtime exposure control |
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| `msaa` | `cargo run -p wsg-lib --example msaa` | MSAA 4× (multisample anti-aliasing, smooth edges) |
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| `fog` | `cargo run -p wsg-lib --example fog --features "all-prims"` | Distance fog (3 modes: linear, exp, exp²) |
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| `dof` | `cargo run -p wsg-lib --example dof --features "all-prims"` | Depth of field (cinematic bokeh, focus presets) |
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> All commands run from the repo root. All effects are **opt-in** — a disabled
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> effect allocates nothing and executes nothing.
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---
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## `demo` — Full Showcase
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Combines **all** effects: LOD primitives, procedural textures, lights
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(directional + point + spot), shadows, HDR/ACES, exposure, emissive, bloom, culling.
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```sh
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cargo run -p wsg-lib --example demo
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```
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### Keys
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| Key | Action |
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|-----|--------|
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| Drag (LMB) | Orbit camera |
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| Wheel | Zoom |
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| `R` | Reset camera |
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| `1` / `2` / `3` | Presets: front / side / top |
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| `+` / `-` | Exposure ×1.3 / ÷1.3 |
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| `0` | Reset exposure |
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---
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## `bloom` — Post-process Bloom
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Two emissive spheres (orange intensity 2.0, blue intensity 3.0) produce a
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visible halo. The cube and floor serve as reference (non-emissive).
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Bloom is a 4-pass GPU pipeline: threshold → blur H → blur V → composite.
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```sh
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cargo run -p wsg-lib --example bloom
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```
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### Keys
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| Key | Action |
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|-----|--------|
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| Drag (LMB) | Orbit camera |
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| Wheel | Zoom |
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| `R` | Reset camera |
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| `+` / `-` | **Bloom threshold** +0.1 / −0.1 |
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| `[` / `]` | **Bloom intensity** +0.1 / −0.1 |
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| `I` / `O` | **Bloom radius** +0.5 / −0.5 |
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| `E` / `Q` | Exposure ×1.3 / ÷1.3 |
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| `0` | Reset exposure |
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### What to observe
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- **Low threshold** (0.0): the entire image "blooms" (very diffuse effect).
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- **High threshold** (2.0+): only the bright emissive spheres produce glow.
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- **Intensity 0.0**: no visible glow (even though the threshold extracts pixels).
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- **Large radius** (10+): the glow spreads over a large area.
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---
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## `hdr` — HDR + Tone Mapping
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Demonstrates HDR rendering with the ACES Filmic curve. Three objects:
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- **Cube**: normal lighting (no emissive) — LDR reference.
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- **Bright sphere** (emissive 3.0): without HDR, it would be clamped to white.
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With ACES, highlights "roll off" smoothly toward white.
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- **Dark sphere** (emissive 0.3): stays dark even at high exposure.
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```sh
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cargo run -p wsg-lib --example hdr
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```
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### Keys
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| Key | Action |
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|-----|--------|
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| Drag (LMB) | Orbit camera |
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| Wheel | Zoom |
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| `R` | Reset camera |
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| `E` | **Exposure ×1.3** (brighter) |
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| `Q` | **Exposure ÷1.3** (darker) |
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| `0` | Reset exposure to 1.0 |
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### What to observe
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- At exposure 1.0: the bright sphere is white but with detail (ACES rolloff).
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- At high exposure (E×E×E): the scene brightens, the bright sphere stays white
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(saturated), but the cube gains detail.
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- At low exposure (Q×Q): everything darkens, the bright sphere becomes orange
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(HDR values > 1.0 are compressed).
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> **Note**: the tone mapper is compiled into the pipeline at build time. To
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> compare ACES vs Reinhard, change `ToneMapper::Aces` → `ToneMapper::Reinhard`
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> in the source.
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---
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## `msaa` — MSAA 4× (Anti-aliasing)
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Demonstrates multisample anti-aliasing: object edges (cube, sphere) are smooth
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instead of "stair-stepped". The scene contains a cube (sharp edges), a sphere
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(curved silhouette), and a small cube near the camera (maximum aliasing).
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```sh
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cargo run -p wsg-lib --example msaa
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```
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### Keys
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| Key | Action |
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|-----|--------|
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| Drag (LMB) | Orbit camera |
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| Wheel | Zoom |
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| `R` | Reset camera |
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| `M` | Show sample count |
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### To compare with/without MSAA
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Remove the `.with_msaa(4)` line in the source and recompile: the scene is
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identical, only the edges differ (stair-stepped vs smooth).
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> **Note**: MSAA is a build-time setting (multisample texture allocation). It
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> works independently of HDR: with HDR, the MSAA texture is `Rgba16Float` and
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> resolves into the HDR texture before bloom/TM.
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---
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## `fog` — Distance Fog
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Demonstrates the 3 fog modes: **linear**, **exponential**, **exponential²**.
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The scene contains a row of cubes receding into the distance and scattered
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spheres on a large floor plane. Fog blends objects toward a background color,
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creating the illusion of an infinite world.
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```sh
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cargo run -p wsg-lib --example fog --features "all-prims"
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```
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**Keys**: `1` = linear, `2` = exp, `3` = exp², `4` = off, `R` = reset.
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> Fog is applied in the main fragment shader (after lighting, before tone
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> mapping). It uses the Euclidean distance from the fragment to the camera.
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---
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## `dof` — Depth of Field (Cinematic Bokeh)
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Demonstrates depth of field blur: an object at the focus plane stays sharp
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while foreground and background blur according to their distance from the
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focus plane. Creates a natural attention effect (cinematic style).
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The scene contains 20 cubes in a row along Z (z=3 to z=-25.5) and 5 spheres to
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the sides, on a floor plane. Focus presets at 3 m / 8 m / 15 m.
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```sh
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cargo run -p wsg-lib --example dof --features "all-prims"
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```
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**Keys**: `1` = cinematic, `2` = subtle, `3` = focus 3 m, `4` = focus 15 m,
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`5` = off, `R` = reset.
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> DoF operates in linear HDR (after bloom, before tone mapping). Two passes:
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> CoC (depth → per-pixel blur radius) then 12-tap disc blur with variable radius.
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