TSL: Fix `positionWorld` used in `material.positionNode` and `fragment-stage` (#30105)

* fix `positionWorld` used in `positionNode` and fragment-stage

* update merge dev

* revision

src/materials/nodes/NodeMaterial.js

@@ -352,7 +352,7 @@ class NodeMaterial extends Material {
 
 		if ( this.positionNode !== null ) {
 
-			positionLocal.assign( this.positionNode );
+			positionLocal.assign( this.positionNode.context( { isPositionNodeInput: true } ) );
 
 		}
 

src/nodes/accessors/Position.js

@@ -30,21 +30,21 @@ export const positionPrevious = /*@__PURE__*/ positionGeometry.varying( 'positio
  *
  * @type {VaryingNode<vec3>}
  */
-export const positionWorld = /*@__PURE__*/ modelWorldMatrix.mul( positionLocal ).xyz.varying( 'v_positionWorld' );
+export const positionWorld = /*@__PURE__*/ modelWorldMatrix.mul( positionLocal ).xyz.varying( 'v_positionWorld' ).context( { needsPositionReassign: true } );
 
 /**
  * TSL object that represents the position world direction of the current rendered object.
  *
  * @type {Node<vec3>}
  */
-export const positionWorldDirection = /*@__PURE__*/ positionLocal.transformDirection( modelWorldMatrix ).varying( 'v_positionWorldDirection' ).normalize().toVar( 'positionWorldDirection' );
+export const positionWorldDirection = /*@__PURE__*/ positionLocal.transformDirection( modelWorldMatrix ).varying( 'v_positionWorldDirection' ).normalize().toVar( 'positionWorldDirection' ).context( { needsPositionReassign: true } );
 
 /**
  * TSL object that represents the vertex position in view space of the current rendered object.
  *
  * @type {VaryingNode<vec3>}
  */
-export const positionView = /*@__PURE__*/ modelViewMatrix.mul( positionLocal ).xyz.varying( 'v_positionView' );
+export const positionView = /*@__PURE__*/ modelViewMatrix.mul( positionLocal ).xyz.varying( 'v_positionView' ).context( { needsPositionReassign: true } );
 
 /**
  * TSL object that represents the position view direction of the current rendered object.

src/nodes/core/VaryingNode.js

@@ -133,7 +133,9 @@ class VaryingNode extends Node {
 		const properties = builder.getNodeProperties( this );
 		const varying = this.setupVarying( builder );
 
-		if ( properties.propertyName === undefined ) {
+		const needsReassign = builder.shaderStage === 'fragment' && properties.reassignPosition === true && builder.context.needsPositionReassign;
+
+		if ( properties.propertyName === undefined || needsReassign ) {
 
 			const type = this.getNodeType( builder );
 			const propertyName = builder.getPropertyName( varying, NodeShaderStage.VERTEX );
@@ -143,6 +145,17 @@ class VaryingNode extends Node {
 
 			properties.propertyName = propertyName;
 
+			if ( needsReassign ) {
+
+				// once reassign varying in fragment stage
+				properties.reassignPosition = false;
+
+			} else if ( properties.reassignPosition === undefined && builder.context.isPositionNodeInput ) {
+
+				properties.reassignPosition = true;
+
+			}
+
 		}
 
 		return builder.getPropertyName( varying );