Add culling for offscreen decals

Source/ConformalDecals/ConformalDecals.csproj

@@ -51,6 +51,7 @@
         </Reference>
     </ItemGroup>
     <ItemGroup>
+        <Compile Include="DecalBoundsBehaviour.cs" />
         <Compile Include="DecalConfig.cs" />
         <Compile Include="DecalIconFixer.cs" />
         <Compile Include="DecalPropertyIDs.cs" />

Source/ConformalDecals/DecalBoundsBehaviour.cs

@@ -0,0 +1,12 @@
+using System;
+using UnityEngine;
+
+namespace ConformalDecals {
+    public class DecalBoundsBehaviour : MonoBehaviour {
+        public ModuleConformalDecal decalRenderer;
+        
+        private void OnWillRenderObject() {
+            decalRenderer._shouldRender = true;
+        }
+    }
+}

Source/ConformalDecals/ModuleConformalDecal.cs

@@ -48,6 +48,8 @@ namespace ConformalDecals {
         /// </remarks>
         [KSPField] public string decalProjector = "Decal-Projector";
 
+        [KSPField] public string decalBounds = "Decal-Bounds";
+
         // Parameters
 
         [KSPField] public bool           scaleAdjustable = true;
@@ -124,7 +126,8 @@ namespace ConformalDecals {
         [KSPField] public Transform decalBackTransform;
         [KSPField] public Transform decalModelTransform;
         [KSPField] public Transform decalProjectorTransform;
-
+        [KSPField] public Transform decalBoundsTransform;
+        
         [KSPField] public Material backMaterial;
         [KSPField] public Vector2  backTextureBaseScale;
 
@@ -139,6 +142,8 @@ namespace ConformalDecals {
 
         private Material _decalMaterial;
         private Material _previewMaterial;
+        
+        internal bool _shouldRender;
 
         private int DecalQueue {
             get {
@@ -203,6 +208,15 @@ namespace ConformalDecals {
                     decalProjectorTransform = part.FindModelTransform(decalProjector);
                     if (decalProjectorTransform == null) throw new FormatException($"Could not find decalProjector transform: '{decalProjector}'.");
                 }
+                
+                // find bounds transform
+                if (string.IsNullOrEmpty(decalBounds)) {
+                    decalBoundsTransform = part.transform;
+                }
+                else {
+                    decalBoundsTransform = part.FindModelTransform(decalBounds);
+                    if (decalBoundsTransform == null) throw new FormatException($"Could not find decalBounds transform: '{decalBounds}'.");
+                }
 
                 // get back material if necessary
                 if (updateBackScale) {
@@ -303,6 +317,9 @@ namespace ConformalDecals {
 
             materialProperties.RenderQueue = DecalQueue;
 
+            var boundsBehaviour = decalBoundsTransform.gameObject.AddComponent<DecalBoundsBehaviour>();
+            boundsBehaviour.decalRenderer = this;
+
             UpdateMaterials();
 
             if (HighLogic.LoadedSceneIsGame) {
@@ -419,6 +436,10 @@ namespace ConformalDecals {
             UpdateScale();
         }
 
+        protected void Update() {
+            _shouldRender = false;
+        }
+
         protected void UpdateScale() {
             var aspectRatio = materialProperties.AspectRatio;
             Vector2 size;
@@ -592,9 +613,9 @@ namespace ConformalDecals {
             }
         }
 
-        protected void Render(Camera camera) {
+        public void Render(Camera camera) {
             if (!_isAttached) return;
-
+            
             // render on each target object
             foreach (var target in _targets) {
                 target.Render(_decalMaterial, part.mpb, camera);