Enhanced UsdGeomModelAPI::ComputeModelDrawMode() to allow more effici…

…ent computation

when the parent's drawMode is known (eg. in a traversal context).

(Internal change: 1905605)

pxr/usd/lib/usdGeom/modelAPI.cpp

@@ -463,24 +463,41 @@ UsdGeomModelAPI::GetConstraintTargets() const
     return constraintTargets;
 }
 
+namespace {
+static 
+bool
+_GetAuthoredDrawMode(const UsdPrim &prim, TfToken *drawMode)
+{
+    // Only check for the attribute on models; don't check the pseudo-root.
+    if (!prim.IsModel() || !prim.GetParent()) {
+        return false;
+    }
+
+    UsdGeomModelAPI modelAPI(prim);
+    UsdAttribute attr = modelAPI.GetModelDrawModeAttr();
+    return attr && attr.Get(drawMode);
+}
+}
+
 TfToken
-UsdGeomModelAPI::ComputeModelDrawMode() const
+UsdGeomModelAPI::ComputeModelDrawMode(const TfToken &parentDrawMode) const
 {
-    // Find the closest applicable model:drawMode among this prim's ancestors.
-    for (UsdPrim curPrim = GetPrim(); curPrim; curPrim = curPrim.GetParent()) {
-        // Only check for the attribute on models; don't check the pseudo-root.
-        if (!curPrim.IsModel() || !curPrim.GetParent()) {
-            continue;
-        }
+    TfToken drawMode;
+
+    if (_GetAuthoredDrawMode(GetPrim(), &drawMode)) {
+        return drawMode;
+    }
 
-        // If model:drawMode is set, use its value; we want the first attribute
-        // we find.
-        UsdGeomModelAPI curModel(curPrim);
-        UsdAttribute attr;
-        TfToken drawMode;
+    if (!parentDrawMode.IsEmpty()) {
+        return parentDrawMode;
+    }
+
+    // Find the closest applicable model:drawMode among this prim's ancestors.
+    for (UsdPrim curPrim = GetPrim().GetParent(); 
+         curPrim; 
+         curPrim = curPrim.GetParent()) {
 
-        if ((attr = curModel.GetModelDrawModeAttr()) && attr &&
-            attr.Get(&drawMode)) {
+        if (_GetAuthoredDrawMode(curPrim, &drawMode)) {
             return drawMode;
         }
     }
@@ -489,5 +506,6 @@ UsdGeomModelAPI::ComputeModelDrawMode() const
     return UsdGeomTokens->default_;
 }
 
+
 PXR_NAMESPACE_CLOSE_SCOPE
 

pxr/usd/lib/usdGeom/modelAPI.h

@@ -589,17 +589,19 @@ class UsdGeomModelAPI : public UsdAPISchemaBase
     /// Otherwise, its computed model:drawMode is that of its closest ancestor
     /// with an authored model:drawMode.
     ///
-    /// This function should be considered a reference implementation for
-    /// correctness. <b>If called on each prim in the context of a traversal
-    /// we will perform massive overcomputation, because sibling prims share
-    /// sub-problems in the query that can be efficiently cached, but are not
-    /// (cannot be) by this simple implementation.</b> If you have control of
-    /// your traversal, it will be far more efficient to manage model:drawMode
-    /// on a stack as you traverse.
-    ///
+    /// If this function is being called in a traversal context to compute 
+    /// the draw mode of an entire hierarchy of prims, it would be beneficial
+    /// to cache and pass in the computed parent draw-mode via the 
+    /// \p parentDrawMode parameter. This avoids repeated upward traversal to 
+    /// look for ancestor opinions.
+    /// 
+    /// When \p parentDrawMode is empty (or unspecified), this function does 
+    /// an upward traversal to find the closest ancestor with an authored 
+    /// model:drawMode.
+    /// 
     /// \sa GetModelDrawModeAttr()
     USDGEOM_API
-    TfToken ComputeModelDrawMode() const;
+    TfToken ComputeModelDrawMode(const TfToken &parentDrawMode=TfToken()) const;
 };
 
 

pxr/usd/lib/usdGeom/wrapModelAPI.cpp

@@ -294,7 +294,8 @@ WRAP_CUSTOM {
         .def("GetConstraintTargets", &UsdGeomModelAPI::GetConstraintTargets,
             return_value_policy<TfPySequenceToList>())
 
-        .def("ComputeModelDrawMode", &UsdGeomModelAPI::ComputeModelDrawMode)
+        .def("ComputeModelDrawMode", &UsdGeomModelAPI::ComputeModelDrawMode,
+            (arg("parentDrawMode")=TfToken()))
     ;
 }