diff --git a/docs/authority-map.md b/docs/authority-map.md
index 235f69e..3731576 100644
--- a/docs/authority-map.md
+++ b/docs/authority-map.md
@@ -19,6 +19,7 @@ drivers, asset-provider hooks, package release, runtime tests, and captures.
 - provider asset-manifest documents
 - runtime-selected asset-variant metadata, including native rendering-program bindings
 - generic field-volume lifecycle declarations and logical texture/scalar/matrix ports
+- generic viewport-to-texture scale bindings between logical vector and texture ports
 - provider command receipts
 - semantic render-channel inclusion and exclusion policy
 - Unity input and local presentation assets
@@ -51,6 +52,13 @@ temporal pass must also advertise its current-sample, history,
 previous-view-projection, and reset-history ports; partial temporal programs fail
 closed.
 
+Viewport-sized shader inputs are likewise presentation state. A provider may
+relate a logical vector port to a logical native texture port through
+`viewportTextureScaleBindings`; EveUnity derives the vector from the active
+camera viewport and resolved texture dimensions on every render. A provider
+literal is not allowed to impersonate those runtime dimensions, and an
+unresolvable relation fails closed.
+
 The provider selects camera semantics and framing from its authoritative mode.
 `planar.top-down-follow.v1` derives a downward presentation from the advertised
 target and framing values. `perspective.entity-forward-follow.v1` derives its
diff --git a/packages/org.gamecult.eve.unity-scene/Runtime/Fields/EveUnityFieldsVolumeRenderer.cs b/packages/org.gamecult.eve.unity-scene/Runtime/Fields/EveUnityFieldsVolumeRenderer.cs
index 2509849..add27f9 100644
--- a/packages/org.gamecult.eve.unity-scene/Runtime/Fields/EveUnityFieldsVolumeRenderer.cs
+++ b/packages/org.gamecult.eve.unity-scene/Runtime/Fields/EveUnityFieldsVolumeRenderer.cs
@@ -20,6 +20,8 @@ namespace GameCult.Eve.UnityScene.Fields
         private Material? _material;
         private Shader? _sourceShader;
         private IReadOnlyDictionary<string, string>? _programMetadata;
+        private readonly Dictionary<string, Texture> _assetTexturesByPort =
+            new Dictionary<string, Texture>(StringComparer.Ordinal);
         private RenderTexture? _raymarchTexture;
         private readonly RenderTexture?[] _historyTextures = new RenderTexture?[2];
         private int _historyTextureIndex = -1;
@@ -89,7 +91,7 @@ namespace GameCult.Eve.UnityScene.Fields
             ApplyFieldBindings(field, _document);
             camera.depthTextureMode |= DepthTextureMode.Depth;
             EnsureVolumeTextures(camera, field);
-            if (_raymarchTexture == null) return;
+            if (_raymarchTexture == null || !ApplyViewportTextureScaleBindings(field, camera)) return;
 
             var gpuProjection = GL.GetGPUProjectionMatrix(camera.projectionMatrix, true);
             var viewProjection = gpuProjection * camera.worldToCameraMatrix;
@@ -168,6 +170,7 @@ namespace GameCult.Eve.UnityScene.Fields
             _sourceShader = shader;
             _activeNodeId = field.NodeId;
             _material = new Material(shader) { hideFlags = HideFlags.DontSave };
+            _assetTexturesByPort.Clear();
             ResetTemporalHistory();
             foreach (var parameter in ParseBindings(Prop(field, "floatParameters")))
             {
@@ -180,7 +183,11 @@ namespace GameCult.Eve.UnityScene.Fields
                 var texture = provider.ResolveAsset(
                     new EveUnityPlayableWorldAssetBinding(binding.Key, "", "provider-asset-ref"),
                     typeof(Texture)) as Texture;
-                if (texture != null) SetTexturePort(binding.Value, texture);
+                if (texture != null)
+                {
+                    _assetTexturesByPort[binding.Value] = texture;
+                    SetTexturePort(binding.Value, texture);
+                }
             }
             var quality = Prop(field, "quality").Trim().ToLowerInvariant();
             if (TryProgramValue($"unity.volume.quality.{quality}.keyword", out var keyword) &&
@@ -262,6 +269,7 @@ namespace GameCult.Eve.UnityScene.Fields
             if (_material != null) { Destroy(_material); _material = null; }
             _sourceShader = null;
             _programMetadata = null;
+            _assetTexturesByPort.Clear();
             _activeNodeId = "";
             PresentedFrameId = -1;
             CompositeCount = 0;
@@ -276,6 +284,36 @@ namespace GameCult.Eve.UnityScene.Fields
 
         private bool HasTemporalProgram() => ProgramPass("temporal") >= 0;
 
+        private bool ApplyViewportTextureScaleBindings(EveUnityFieldVolumeProjection field, Camera camera)
+        {
+            foreach (var binding in ParseBindings(Prop(field, "viewportTextureScaleBindings")))
+            {
+                if (string.IsNullOrWhiteSpace(ProgramPort("vector", binding.Key)) ||
+                    string.IsNullOrWhiteSpace(ProgramPort("texture", binding.Value)) ||
+                    !_assetTexturesByPort.TryGetValue(binding.Value, out var texture) ||
+                    !TryComputeViewportTextureScale(camera.pixelWidth, camera.pixelHeight, texture, out var scale))
+                    return false;
+                SetVectorPort(binding.Key, scale);
+            }
+            return true;
+        }
+
+        public static bool TryComputeViewportTextureScale(
+            int viewportWidth,
+            int viewportHeight,
+            Texture? texture,
+            out Vector4 scale)
+        {
+            scale = default;
+            if (texture == null || texture.width <= 0 || texture.height <= 0) return false;
+            scale = new Vector4(
+                (float)Math.Max(1, viewportWidth) / texture.width,
+                (float)Math.Max(1, viewportHeight) / texture.height,
+                0f,
+                0f);
+            return true;
+        }
+
         private static bool EnsureRenderTexture(ref RenderTexture? texture, int width, int height, string name)
         {
             if (texture != null && texture.width == width && texture.height == height) return false;
diff --git a/packages/org.gamecult.eve.unity-scene/Tests/Editor/EveFieldsUnitySceneProjectionTests.cs b/packages/org.gamecult.eve.unity-scene/Tests/Editor/EveFieldsUnitySceneProjectionTests.cs
index 25fd08b..cf10e64 100644
--- a/packages/org.gamecult.eve.unity-scene/Tests/Editor/EveFieldsUnitySceneProjectionTests.cs
+++ b/packages/org.gamecult.eve.unity-scene/Tests/Editor/EveFieldsUnitySceneProjectionTests.cs
@@ -73,6 +73,25 @@ namespace GameCult.Eve.UnityScene.Tests
             Assert.That(error, Does.Contain("history port"));
         }
 
+        [Test]
+        public void VolumeRendererDerivesViewportTextureScaleFromNativeDimensions()
+        {
+            var texture = new Texture2D(128, 64, TextureFormat.RGBA32, false);
+            try
+            {
+                Assert.That(EveUnityFieldsVolumeRenderer.TryComputeViewportTextureScale(
+                    640,
+                    360,
+                    texture,
+                    out var scale), Is.True);
+                Assert.That(scale, Is.EqualTo(new Vector4(5f, 5.625f, 0f, 0f)));
+            }
+            finally
+            {
+                UnityEngine.Object.DestroyImmediate(texture);
+            }
+        }
+
         [Test]
         public void PackageContainsGenericFieldsShader()
         {
diff --git a/packages/org.gamecult.eve.unity-scene/package.json b/packages/org.gamecult.eve.unity-scene/package.json
index b2951a7..5e9720a 100644
--- a/packages/org.gamecult.eve.unity-scene/package.json
+++ b/packages/org.gamecult.eve.unity-scene/package.json
@@ -1,7 +1,7 @@
 {
     "name": "org.gamecult.eve.unity-scene",
     "displayName": "Eve Unity Scene Lowering",
-    "version": "0.3.39",
+    "version": "0.3.40",
     "unity": "2021.3",
     "description": "Provider-agnostic Unity scene shell for gamecult.eve.surface.v1 interactive world surfaces.",
     "dependencies": {