CNN v2: Add mip-level support to runtime effect

Binary format v2 includes mip_level in header (20 bytes, was 16).
Effect reads mip_level and passes to static features shader via uniform.
Shader samples from correct mip texture based on mip_level.

Changes:
- export_cnn_v2_weights.py: Header v2 with mip_level field
- cnn_v2_effect.h: Add StaticFeatureParams, mip_level member, params buffer
- cnn_v2_effect.cc: Read mip_level from weights, create/bind params buffer, update per-frame
- cnn_v2_static.wgsl: Accept params uniform, sample from selected mip level

Binary format v2:
- Header: 20 bytes (magic, version=2, num_layers, total_weights, mip_level)
- Backward compatible: v1 weights load with mip_level=0

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 20 insertions, 5 deletions

diff --git a/workspaces/main/shaders/cnn_v2/cnn_v2_static.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_static.wgsl
index 7a9e6de..f71fad2 100644
--- a/workspaces/main/shaders/cnn_v2/cnn_v2_static.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_static.wgsl
@@ -1,13 +1,19 @@
 // CNN v2 Static Features Compute Shader
 // Generates 8D parametric features: [p0, p1, p2, p3, uv.x, uv.y, sin10_x, bias]
-// p0-p3: Parametric features (currently RGBD from mip0, could be mip1/2, gradients, etc.)
+// p0-p3: Parametric features from specified mip level (0=mip0, 1=mip1, 2=mip2, 3=mip3)
 // Note: Input image RGBD (mip0) fed separately to Layer 0
 
+struct StaticFeatureParams {
+  mip_level: u32,
+  padding: vec3<u32>,
+}
+
 @group(0) @binding(0) var input_tex: texture_2d<f32>;
 @group(0) @binding(1) var input_tex_mip1: texture_2d<f32>;
 @group(0) @binding(2) var input_tex_mip2: texture_2d<f32>;
 @group(0) @binding(3) var depth_tex: texture_2d<f32>;
 @group(0) @binding(4) var output_tex: texture_storage_2d<rgba32uint, write>;
+@group(0) @binding(5) var<uniform> params: StaticFeatureParams;
 
 @compute @workgroup_size(8, 8)
 fn main(@builtin(global_invocation_id) id: vec3<u32>) {
@@ -18,10 +24,19 @@ fn main(@builtin(global_invocation_id) id: vec3<u32>) {
     return;
   }
 
-  // Parametric features (p0-p3)
-  // TODO: Experiment with mip1 grayscale, Sobel gradients, etc.
-  // For now, use RGBD from mip 0 (same as input, but could differ)
-  let rgba = textureLoad(input_tex, coord, 0);
+  // Parametric features (p0-p3) - sample from specified mip level
+  var rgba: vec4<f32>;
+  if (params.mip_level == 0u) {
+    rgba = textureLoad(input_tex, coord, 0);
+  } else if (params.mip_level == 1u) {
+    rgba = textureLoad(input_tex_mip1, coord, 0);
+  } else if (params.mip_level == 2u) {
+    rgba = textureLoad(input_tex_mip2, coord, 0);
+  } else {
+    // Mip 3 or higher: use mip 2 as fallback
+    rgba = textureLoad(input_tex_mip2, coord, 0);
+  }
+
   let p0 = rgba.r;
   let p1 = rgba.g;
   let p2 = rgba.b;