Applying MaterialBindingAPI causes excessive recomposition

[deboisj]

Description of Issue

Applying the MaterialBindingAPI api on prims is very expensive, by causing seemingly unecessary recomposition (?). See script bellow. Binding material without the schema applies is orders of magnitudes faster.

Also see this thread on the google-usd interest group where this issue was discussed : https://groups.google.com/g/usd-interest/c/kEnzWToBwnQ

Steps to Reproduce

from pxr import Usd, UsdShade, Sdf
import time

print("USD VERSION : " + str(Usd.GetVersion()))

def test(apply):
	print("---------------------------------")
	print("APPLYING SCHEMA : " + str(apply))

	stage = Usd.Stage.CreateInMemory()
	stage.DefinePrim("/root", "Xform")

	mat = UsdShade.Material.Define(stage, '/root/mat')
	shader = UsdShade.Shader.Define(stage, '/root/mat/usdps')
	shader.CreateIdAttr("UsdPreviewSurface")
	shader.CreateInput("diffuseColor", Sdf.ValueTypeNames.Float3).Set((1,0,0))
	mat.CreateSurfaceOutput().ConnectToSource(shader.ConnectableAPI(), "surface")

	primCount = 10000

	primPaths = []

	for i in range(primCount):
		p =  "/root/Object" + str(i)
		stage.DefinePrim(p, "Sphere")
		primPaths.append(p)

	startTime = time.time()
	for p in primPaths:
		prim = stage.GetPrimAtPath(p);
		if apply:
			prim.ApplyAPI(UsdShade.MaterialBindingAPI)
		UsdShade.MaterialBindingAPI(prim).Bind(mat)

	endTime = time.time()

	elapsed_time = endTime - startTime
	print('Execution time:', elapsed_time, 'seconds')
	# stage.Export("D:/tmp/test" + str(apply) + ".usda")
	
	

test(False) # only binding
test(True) # apply + binding

print("All done.")

On my end I get this output :

USD VERSION : (0, 22, 11)
---------------------------------
APPLYING SCHEMA : False
Execution time: 0.33567094802856445 seconds
---------------------------------
APPLYING SCHEMA : True
Execution time: 14.84079122543335 seconds
All done.

System Information (OS, Hardware)

Windows

Package Versions

22.11

[tallytalwar]

Filed as internal issue #USD-8131