Multi pass

SHADER_CONTRACT.md

@@ -152,10 +152,23 @@ Pass fields:
 - `id`: required pass identifier. It must be a valid shader identifier and unique inside the package.
 - `source`: required Slang source path relative to the package directory.
 - `entryPoint`: optional Slang function for this pass. Defaults to the package-level `entryPoint`.
-- `inputs`: optional list of named inputs. Current reserved names include `layerInput` and future pass output names.
+- `inputs`: optional list of named inputs. The first input is used as the pass input texture.
 - `output`: optional output name. Use `layerOutput` for the final visible layer result.
 
-Current runtime note: pass manifests are parsed and every declared pass is Slang-validated/compiled, but execution still uses the first pass until multipass render-target routing is enabled. Existing single-pass shaders are unaffected.
+Pass input names:
+
+- `layerInput`: the input to this layer, before any of its passes run.
+- `previousPass`: the previous pass output in this layer. If there is no previous pass, this falls back to `layerInput`.
+- Any earlier pass `id` or `output` name from the same layer.
+
+If `inputs` is omitted, the first pass samples `layerInput` and later passes sample `previousPass`.
+
+Pass output names:
+
+- `layerOutput`: the final visible output of this layer.
+- Any other name creates an intermediate 16-bit float render target that later passes may sample.
+
+If the final declared pass does not explicitly output `layerOutput`, the runtime still treats that final pass as the visible layer output. Existing single-pass shaders are unaffected.
 
 ## Slang Entry Point