prgpu 0.1.16

GPU-accelerated rendering utilities for Adobe Premiere Pro and After Effects plugins
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

# `RenderGraph<F>` — declarative pipeline

Effects describe their multi-pass pipeline once in `Effect::pipeline`. The
adapter caches the graph for the effect instance's lifetime and runs it
against each frame's `FrameData` via `prgpu::graph::execute()`.

```rust
fn pipeline(g: &mut RenderGraph<FrameData>) {
    g.set_source_policy(SourcePolicy::SnapshotIfAliased { tag: SOURCE_TAG });

    let bloom = g.declare_mip_pyramid("bloom", |ctx| {
        let q = Quality::from_index(ctx.frame_data().quality);
        let (scale, levels) = q.pyramid_layout();
        let (w, h) = base_dims(ctx.output_width(), ctx.output_height(), scale);
        MipPyramidDesc::new(w, h)
            .levels(actual_levels(levels, w, h))
            .tag(BLOOM_TAG)
    });

    g.add_pass("prefilter",
        k::bloom_prefilter::kernel(),
        Slot::MainSource, bloom.mip(0),
        |ctx| ctx.frame_data().prefilter);

    g.add_mip_chain("downsample", bloom, MipDirection::Down,
        k::bloom_downsample::kernel(),
        |level, _ctx| BloomDownsampleParams { src_lod: level, .. });

    g.add_mip_chain("upsample", bloom, MipDirection::Up,
        k::bloom_upsample::kernel(),
        |level, ctx| { let mut up = ctx.frame_data().upsample; up.dst_lod = level; up });

    g.add_pass_with_input("composite",
        k::composite::kernel(),
        Slot::MainSource, bloom.mip(0), Slot::Output,
        |ctx| ctx.frame_data().composite);
}
```

## Resources

| Method                         | Returns                       | Purpose |
|--------------------------------|-------------------------------|---------|
| `declare_mip_pyramid(name, f)` | `ResourceHandle<MipPyramid>`  | N-level pyramid sized by per-frame closure |

The descriptor closure receives a `MipPyramidCtx<F>` exposing
`frame_data()`, `output_width/height()`, `bytes_per_pixel()`. Returning
`MipPyramidDesc::new(w, h).levels(N).tag(T)` keys the allocation in the
prgpu buffer pool — same `tag` reuses the same physical buffer across
renders.

## Slots

A `Slot` resolves to a `FrameBinding` at execution time:

| Variant                        | Resolves to                                      |
|--------------------------------|--------------------------------------------------|
| `Slot::MainSource`             | `base.main_source` (after source-snapshot policy) |
| `Slot::Output`                 | `base.output`                                    |
| `bloom.mip(lod)`               | A specific mip level of the pyramid resource     |
| `bloom.whole()`                | The whole pyramid (mip-aware sampling)           |
| `Slot::Inline(FrameBinding)`   | A pre-built binding (test fixtures, snapshots)   |

## Single-pass

```rust
g.add_pass(name, kernel, source, target, |ctx| params);
g.add_pass_with_input(name, kernel, source, input, target, |ctx| params);
```

`source` binds slot 0 (`outgoing`), `input` (when given) binds slot 1
(`incoming`), `target` binds slot 2 (`dest`). When no `input` is given,
slot 1 mirrors slot 0 — matches the "either source-only or
source+secondary" pattern Slang kernels expect.

The `params` closure receives a `PassContext<F>` and returns the kernel's
constant-buffer params for this frame.

## Mip chains

```rust
g.add_mip_chain(name, resource, MipDirection::Down, kernel, |level, ctx| params);
g.add_mip_chain(name, resource, MipDirection::Up,   kernel, |level, ctx| params);
```

For an N-level pyramid, the chain runs N-1 dispatches. `Down` walks
`lod 0 → 1 → ... → N-1`; `Up` walks the reverse. The closure receives the
source `level` for `Down` and the destination `level` for `Up`.

## Source-snapshot policy

```rust
g.set_source_policy(SourcePolicy::SnapshotIfAliased { tag });
```

| Variant                              | Behaviour |
|--------------------------------------|-----------|
| `SourcePolicy::Direct`               | No snapshot. Use when source/output are guaranteed distinct. |
| `SourcePolicy::SnapshotIfAliased { tag }` | Snapshot only when host signals `Capability::SourceOutputMayAlias` (Premiere GPU). |
| `SourcePolicy::AlwaysSnapshot { tag }`    | Snapshot unconditionally. Useful for pipelines that read source after writing back through it. |

See [`source_snapshot.md`](source_snapshot.md) for details.

## Execution

```rust
prgpu::graph::execute(graph, frame_data, base) -> Result<(), GraphError>
```

The executor:

1. Clones `base` (so it can rebind `main_source` to a snapshot).
2. Applies `source_policy`.
3. Allocates each declared resource via `cpu::buffer` or `gpu::buffer`
   based on `base.backend`.
4. Walks `passes` in declaration order. Each pass:
   - resolves slot bindings against `base` + the resource table,
   - builds a `Configuration` via `ConfigBuilder`,
   - calls the type-erased dispatcher closure (which knows the kernel +
     param closure + backend branch).

`GraphError` short-circuits the whole render — a failed pass aborts cleanly
instead of producing a partial output.

## Why static + dynamic

The graph **structure** (resources, passes, mip chains, source policy) is
declared once. Per-frame **behaviour** comes from closures: param
extractors, mip-pyramid sizing, and (future) `enabled_when` predicates.
Don't rebuild the graph every frame just to disable a pass — wire it
through a closure that returns zero-strength params, or guard with an
`enabled_when` predicate when that lands.

## Validation

The executor validates lazily: missing target, unknown resource, mip
level out of range, or bad config build all return a `GraphError`
identifying the offending pass.