Jérôme Bousquié
53 lines
1.9 KiB
Markdown
53 lines
1.9 KiB
Markdown
# Cameras & Camera-Driven Rendering
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Examples where the **camera** drives what gets rendered.
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| Example | Run command | What it shows |
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|---------|-------------|---------------|
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| `culling` | `cargo run -p wsg-lib --example culling` | GPU-driven frustum culling: a 15×15 grid of cubes, off-frustum objects skipped |
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> All commands run from the repo root.
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The frustum is defined by the camera's view-projection matrix, so frustum
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culling is inherently a camera concept: move the camera and the set of drawn
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objects changes — with **zero CPU cost** (the GPU decides in a compute pass).
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---
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## `culling` — GPU Frustum Culling
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A grid of **15×15 = 225 cubes** is placed on a large floor. The GPU-driven
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culling (compute shader) determines which cubes are visible in the camera
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frustum and zeros their indirect draw args — **zero CPU cost**.
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```sh
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cargo run -p wsg-lib --example culling
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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 (look around) |
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| Wheel | Zoom in/out |
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| `R` | Reset (top view) |
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| `1` | Front view (cubes behind are culled) |
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| `2` | Side view |
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| `3` | **Top view** (see the full grid) |
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### What to observe
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- In top view (`3`): the entire grid is visible.
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- Orbit to 90°: cubes behind the camera **are not drawn** (culled).
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- Zoom very close: only cubes near the near plane are rendered.
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- Cubes rotate slowly (staggered phases) → culling is dynamic (a cube can
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enter/leave the frustum during a frame).
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> **Note**: culling is enabled via `AppBuilder::with_culling(true)`. Changing
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> it to `false` in the source disables culling (all cubes are always drawn,
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> even off-screen).
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>
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> The GPU-driven pipeline (compute matrices → culling → indirect draws) is
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> documented in [`docs/tech/ARCHI_CPU_GPU.md`](../../../docs/tech/ARCHI_CPU_GPU.md)
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> and [`docs/user/cameras/gpu-driven.md`](../../../docs/user/cameras/gpu-driven.md).
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