MAYA-128599 fixing pivot command

doc/USD Transforms Stack.md

@@ -0,0 +1,74 @@
+# USD Transforms Stack
+
+## Take Aways
+
+- Understand the USD transform stack (xformOp)
+- Know the available USD transform ops
+- Know the structure of the USD transform stack
+- Know how it maps to UFE
+- Know the various implementations of xformOp in MayaUSD
+
+## What is a USD Transform stack
+
+- Control the 3D position of a USD prim
+- It is  an ordered list of transform operations (xformOp):
+  translation, rotation, scale, 4x4 matrix
+- USD supports any number of xformOp, in any order
+- An individual xformOp is kept in a USD attribute
+- All transform-related attributes begin with the "xformOp:" prefix
+- An xformOp attribute name has two or three parts:
+    - "xformOp:"
+    - the transform type
+    - optional suffix
+- For example: "xformOp:translate:pivot"
+- The xformOp order is kept in a special attribute: "xformOpOrder"
+
+## Quick Recap on Pivot
+
+Pivots...
+
+- ... are generally neutral: they don't move the prim
+- ... come as a pair of opposite translations, sandwhiching other transforms
+- ... are used in DCC to position the center of rotation and center of scaling
+
+## Quick Recap on Transform Maths
+
+- A single matrix is equivalent to any number of chained transforms
+- The inverse is not true
+- Some matrices cannot be expressed with translation, rotation and scaling...
+- ... but they are generally considered degenerate and are rarely seen
+- On the other hand, matrix cannot express pivot pairs, since they are neutral
+- In general, except for pivots, all transform representations are equivalent
+
+## USD Common Transform Stack
+
+- USD provides a recommended, simple transform stack it calls the "common API"
+- The goal is to have a baseline transform stack that all DCC should support
+- The USD common stack structure is: translate, pivot, rotate, scale
+- In particular, the pivot wraps both the rotation and scaling, unlike Maya
+
+## UFE Transforms
+
+UFE Transform3d ...
+
+- ... allows modifying a UFE scene item transforms
+- ... is created by the registered UFE Transform3dHandler
+- ... creates commands that when executed changes the transform
+- ... does *not* prescribe how the various transforms interact
+- ... is implicitly tied to Maya's view of how transforms are ordered
+
+## MayaUSD XformOp Implementations
+
+- MayaUSD provides multiple UFE Transform3d implementations
+- The implementations are: point instance, Maya stack, USD common API, 4x4 matrix and no comprendo + Maya stack
+- For the rest of the presentation, we will ignore point instance and no comprendo
+
+## MayaUSD XformOp Details
+
+- Only the Maya stack supports all the UFE commands. In particular, pivot commands
+- Which one is used is decided at the time of the creation of the Transform3d
+- Once decided, there is no turning back, we cannot switch dynamically
+- The decision is based on what is already authored on the prim
+- In case multiple implementations could be used, the priority order is: Maya stack, common API, matrix
+- The main goal was that we would privilege the Maya stack, but still support the others representations
+- One design decision is to *not* convert between representations

lib/mayaUsd/fileio/utils/xformStack.cpp

@@ -437,10 +437,11 @@ UsdMayaXformStack::MatchingSubstack(const std::vector<UsdGeomXformOp>& xformops)
 
         if (GetNameMatters()) {
             // First try the fast attrName lookup...
-            const auto foundTokenIdxPairIter
-                = _sharedData->m_attrNamesToIdxs.find(xformOp.GetName());
+            const TfToken& opName = xformOp.GetName();
+            const auto     foundTokenIdxPairIter = _sharedData->m_attrNamesToIdxs.find(opName);
             if (foundTokenIdxPairIter == _sharedData->m_attrNamesToIdxs.end()) {
                 // Couldn't find the xformop in our stack, abort
+                // TF_WARN("Cannot find xform op %s", opName.GetText());
                 return _NO_MATCH;
             }
 
@@ -455,13 +456,21 @@ UsdMayaXformStack::MatchingSubstack(const std::vector<UsdGeomXformOp>& xformops)
             } else {
                 // The result we found is before an earlier-found op,
                 // so it doesn't match our stack... abort.
+                // TF_WARN(
+                //     "Cannot find index of xform op %s at %ld between [%ld, %ld]",
+                //     opName.GetText(),
+                //     long(nextOpIndex),
+                //     long(foundIdxPair.first),
+                //     long(foundIdxPair.second));
                 return _NO_MATCH;
             }
 
             assert(foundOpIdx != NO_INDEX);
+            // TF_STATUS("Found xform op %s at %ld", opName.GetText(), long(foundOpIdx));
 
             // Now check that the op type matches...
             if (!GetOps()[foundOpIdx].IsCompatibleType(xformOp.GetOpType())) {
+                // TF_WARN("Incorrect type for xform op %s", opName.GetText());
                 return _NO_MATCH;
             }
         } else {
@@ -489,7 +498,10 @@ UsdMayaXformStack::MatchingSubstack(const std::vector<UsdGeomXformOp>& xformops)
     // check pivot pairs
     TF_FOR_ALL(pairIter, GetInversionTwins())
     {
-        if (opNamesFound[pairIter->first] != opNamesFound[pairIter->second]) {
+        const size_t firstIdx = pairIter->first;
+        const size_t secondIdx = pairIter->second;
+        if (opNamesFound[firstIdx] != opNamesFound[secondIdx]) {
+            // TF_WARN("Unmatched pivot pairs at [%ld, %ld]", firstIdx, secondIdx);
             return _NO_MATCH;
         }
     }
@@ -519,36 +531,45 @@ const UsdMayaXformStack& UsdMayaXformStack::MayaStack()
 {
     static UsdMayaXformStack mayaStack(
         // ops
-        { UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->translate, UsdGeomXformOp::TypeTranslate),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->rotatePivotTranslate, UsdGeomXformOp::TypeTranslate),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->rotatePivot, UsdGeomXformOp::TypeTranslate),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->rotate, UsdGeomXformOp::TypeRotateXYZ),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->rotateAxis, UsdGeomXformOp::TypeRotateXYZ),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->rotatePivot,
-              UsdGeomXformOp::TypeTranslate,
-              true /* isInvertedTwin */),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->scalePivotTranslate, UsdGeomXformOp::TypeTranslate),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->scalePivot, UsdGeomXformOp::TypeTranslate),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->shear, UsdGeomXformOp::TypeTransform),
-          UsdMayaXformOpClassification(UsdMayaXformStackTokens->scale, UsdGeomXformOp::TypeScale),
-          UsdMayaXformOpClassification(
-              UsdMayaXformStackTokens->scalePivot,
-              UsdGeomXformOp::TypeTranslate,
-              true /* isInvertedTwin */) },
+        {
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->translate, UsdGeomXformOp::TypeTranslate),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->pivot, UsdGeomXformOp::TypeTranslate),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->rotatePivotTranslate, UsdGeomXformOp::TypeTranslate),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->rotatePivot, UsdGeomXformOp::TypeTranslate),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->rotate, UsdGeomXformOp::TypeRotateXYZ),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->rotateAxis, UsdGeomXformOp::TypeRotateXYZ),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->rotatePivot,
+                UsdGeomXformOp::TypeTranslate,
+                true /* isInvertedTwin */),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->scalePivotTranslate, UsdGeomXformOp::TypeTranslate),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->scalePivot, UsdGeomXformOp::TypeTranslate),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->shear, UsdGeomXformOp::TypeTransform),
+            UsdMayaXformOpClassification(UsdMayaXformStackTokens->scale, UsdGeomXformOp::TypeScale),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->scalePivot,
+                UsdGeomXformOp::TypeTranslate,
+                true /* isInvertedTwin */),
+            UsdMayaXformOpClassification(
+                UsdMayaXformStackTokens->pivot,
+                UsdGeomXformOp::TypeTranslate,
+                true /* isInvertedTwin */),
+        },
 
         // inversionTwins
         {
-            { 2, 5 },
-            { 7, 10 },
+            { 1, 12 },
+            { 3, 6 },
+            { 8, 11 },
         });
 
     return mayaStack;

lib/mayaUsd/ufe/UsdTransform3dMayaXformStack.cpp

@@ -75,6 +75,8 @@ PXR_NS::UsdAttribute getUsdPrimAttribute(const UsdPrim& prim, const TfToken& att
 const std::unordered_map<TfToken, UsdTransform3dMayaXformStack::OpNdx, TfToken::HashFunctor>
     gOpNameToNdx {
         { TfToken("xformOp:translate"), UsdTransform3dMayaXformStack::NdxTranslate },
+        // Note: this matches the USD common xformOp name.
+        { TfToken("xformOp:translate:pivot"), UsdTransform3dMayaXformStack::NdxPivot },
         { TfToken("xformOp:translate:rotatePivotTranslate"),
           UsdTransform3dMayaXformStack::NdxRotatePivotTranslate },
         { TfToken("xformOp:translate:rotatePivot"), UsdTransform3dMayaXformStack::NdxRotatePivot },
@@ -97,7 +99,10 @@ const std::unordered_map<TfToken, UsdTransform3dMayaXformStack::OpNdx, TfToken::
         { TfToken("xformOp:transform:shear"), UsdTransform3dMayaXformStack::NdxShear },
         { TfToken("xformOp:scale"), UsdTransform3dMayaXformStack::NdxScale },
         { TfToken("!invert!xformOp:translate:scalePivot"),
-          UsdTransform3dMayaXformStack::NdxScalePivotInverse }
+          UsdTransform3dMayaXformStack::NdxScalePivotInverse },
+        // Note: this matches the USD common xformOp name.
+        { TfToken("!invert!xformOp:translate:pivot"),
+          UsdTransform3dMayaXformStack::NdxPivotInverse }
     };
 
 } // namespace

lib/mayaUsd/ufe/UsdTransform3dMayaXformStack.h

@@ -41,6 +41,7 @@ class MAYAUSD_CORE_PUBLIC UsdTransform3dMayaXformStack : public UsdTransform3dBa
     enum OpNdx
     {
         NdxTranslate = 0,
+        NdxPivot,
         NdxRotatePivotTranslate,
         NdxRotatePivot,
         NdxRotate,
@@ -51,6 +52,7 @@ class MAYAUSD_CORE_PUBLIC UsdTransform3dMayaXformStack : public UsdTransform3dBa
         NdxShear,
         NdxScale,
         NdxScalePivotInverse,
+        NdxPivotInverse,
         NbOpNdx
     };
 

lib/usd/ui/layerEditor/mayaSessionState.cpp

@@ -82,9 +82,11 @@ bool MayaSessionState::getStageEntry(StageEntry* out_stageEntry, const MString&
 
     MObject shapeObj;
     MStatus status = UsdMayaUtil::GetMObjectByName(shapePath, shapeObj);
-    CHECK_MSTATUS_AND_RETURN(status, false);
+    if (!status)
+        return false;
     MFnDagNode dagNode(shapeObj, &status);
-    CHECK_MSTATUS_AND_RETURN(status, false);
+    if (!status)
+        return false;
 
     if (const UsdMayaUsdPrimProvider* usdPrimProvider
         = dynamic_cast<const UsdMayaUsdPrimProvider*>(dagNode.userNode())) {
@@ -303,7 +305,7 @@ void MayaSessionState::loadSelectedStage()
 #if defined(WANT_UFE_BUILD)
     const std::string shapePath = MayaUsd::LayerManager::getSelectedStage();
     StageEntry        entry;
-    if (getStageEntry(&entry, shapePath.c_str())) {
+    if (!shapePath.empty() && getStageEntry(&entry, shapePath.c_str())) {
         setStageEntry(entry);
     }
 #endif