feat(cnn_v3): Phase 3 complete — WGSL U-Net inference shaders

5 compute shaders + cnn_v3/common snippet:
  enc0: Conv(20→4,3×3) + FiLM + ReLU             full-res
  enc1: AvgPool + Conv(4→8,3×3) + FiLM + ReLU    half-res
  bottleneck: AvgPool + Conv(8→8,1×1) + ReLU     quarter-res
  dec1: NearestUp + cat(enc1) + Conv(16→4) + FiLM half-res
  dec0: NearestUp + cat(enc0) + Conv(8→4) + FiLM + Sigmoid full-res

Parity rules: zero-pad conv, AvgPool down, NearestUp, FiLM after
conv+bias, skip=concat, OIHW weights+bias layout. Matches PyTorch
train_cnn_v3.py forward() exactly.

Registered in workspaces/main/assets.txt + src/effects/shaders.cc.
Weight layout + Params struct documented in cnn_v3/docs/HOWTO.md §7.

Next: Phase 4 — C++ CNNv3Effect + FiLM uniform upload.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/cnn_v3/shaders/cnn_v3_common.wgsl b/cnn_v3/shaders/cnn_v3_common.wgsl
new file mode 100644
index 0000000..54b0f3d
--- /dev/null
+++ b/cnn_v3/shaders/cnn_v3_common.wgsl
@@ -0,0 +1,23 @@
+// CNN v3 shared helpers — included by all inference compute shaders.
+// Requires the host shader to declare:
+//   @group(?) @binding(?) var<storage, read> weights: array<u32>;
+
+// Read one f16 value from the packed-f16 weights buffer.
+// `base`  — weight_offset from Params (f16 index of the layer start)
+// `idx`   — local f16 index within the layer (conv weight or bias)
+fn get_w(base: u32, idx: u32) -> f32 {
+    let i = base + idx;
+    let v = unpack2x16float(weights[i >> 1u]);
+    return select(v.y, v.x, (i & 1u) == 0u);
+}
+
+// Unpack 8 f16 channels from an rgba32uint texel (pack2x16float layout:
+//   u32[0]=ch0|ch1, u32[1]=ch2|ch3, u32[2]=ch4|ch5, u32[3]=ch6|ch7)
+fn unpack_8ch(tex: texture_2d<u32>, coord: vec2i) -> array<f32, 8> {
+    let t  = textureLoad(tex, coord, 0);
+    let v0 = unpack2x16float(t.x);
+    let v1 = unpack2x16float(t.y);
+    let v2 = unpack2x16float(t.z);
+    let v3 = unpack2x16float(t.w);
+    return array<f32, 8>(v0.x, v0.y, v1.x, v1.y, v2.x, v2.y, v3.x, v3.y);
+}