[vtkusers] Animation performance with cell color

[Flagada]

Hi all !
I am trying to animate a mesh deformation with quite a large number of
nodes (about 300000).
For now the best solution I have found is to make a list containing the
vtkpoints for each animation frame and loop by changing the vtkpoints of
the displayed polydata (or unstructuredgrid).
On a simple model without applying any color to the cells I can obtain an
animation rate of about 50fps wich is a good frame rate for me.
But if I apply colors with a PolyData.GetCellData().SetScalars() the
framerate goes down to 13fps.
Does anybody knows if it could be a better method to display mesh animation
or to improve the display rate of a mesh with colors ?

Here below is the python code I use.
It draws a disk of 800x400 nodes and if you press on F1 it animates a kind
of sinus wave.
First it calculate each frame, then it display the animation without color
and finally it display the animation with random color on cells.

Thanks !

############################

import vtk
import math
from time import time
import random

############################
# Creating disk mesh
disk = vtk.vtkDiskSource()
disk.SetInnerRadius(0.1)
disk.SetOuterRadius(2.0)
disk.SetRadialResolution(400)
disk.SetCircumferentialResolution(800)
disk.Update()
PolyData = disk.GetOutput()

print("%d nodes" % PolyData.GetNumberOfPoints())
print("%d elms" % PolyData.GetNumberOfCells())

# Setup actor and mapper
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(PolyData)
actor = vtk.vtkActor()
actor.SetMapper(mapper)

# Setup render window, renderer, interactor and camera
renderer = vtk.vtkRenderer()
renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)
renderWindowInteractor = vtk.vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)
style = vtk.vtkInteractorStyleTrackballCamera()
renderWindowInteractor.SetInteractorStyle(style)
camera = vtk.vtkCamera()
camera.Elevation(-45)
renderer.SetActiveCamera(camera)

#################################

def KeyPress(object, event):
if object.GetInteractor().GetKeySym() == "F1":
# Calculate each frame and store the vtkPoints into vtkPointsList
PolyData = disk.GetOutput()
vtkPointsList = {}

print("Calculate...")

for ph in range(0, 360, 20):
start_time = time()
vtkPointsList[ph] = vtk.vtkPoints()
vtkPointsList[ph].DeepCopy(PolyData.GetPoints())
for i in range(0, PolyData.GetNumberOfPoints()):
NodePos = vtkPointsList[ph].GetPoint(i)
vtkPointsList[ph].SetPoint(i, NodePos[0], NodePos[1], 0.3 *
math.sin(NodePos[0] * 2 + ph * math.pi / 180))
PolyData.SetPoints(vtkPointsList[ph])
renderWindow.Render()

print("Done. Animate.")

# First animation without color
start_time = time()
for ph in range(0, 360, 20):
PolyData.SetPoints(vtkPointsList[ph])
renderWindow.Render()
print("%.2f FPS" % (18 / (time() - start_time)))

# Activate cells colors
ELMcolors = vtk.vtkUnsignedCharArray()
ELMcolors.SetNumberOfComponents(3)
ELMcolors.SetName("Colors")
for i in range(0, PolyData.GetNumberOfCells()):
ELMcolors.InsertNextTuple([random.random() * 255, random.random()
* 255, random.random() * 255])
PolyData.GetCellData().SetScalars(ELMcolors)

# Second animation with color
start_time = time()
for ph in range(0, 360, 20):
PolyData.SetPoints(vtkPointsList[ph])
renderWindow.Render()
print("%.2f FPS" % (18 / (time() - start_time)))

####################################

style.AddObserver("KeyPressEvent", KeyPress)

renderer.AddActor(actor)
renderWindow.Render()
renderer.ResetCamera()
renderWindowInteractor.Start()

############################

[mmusy]

I only see a drop from 60 fps to 40fps
(with vtk 8.1.1, python 3.6, ubuntu workstation)




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[Ken Martin]

Unfortunately changing the points causes a lot of recomputation for cell
coloring which is what you are using. It is because the changing points
could make a triangle become degenerate (which opengl does not count as a
cell, while VTK does)

If you have the memory on the GPU you could instead create an array of
actors, each with their own mappers and polydata and then loop over them by
changing their visibility (e.g. all are visibleOff except the current time
step). If that fits in memory it should be very fast.

Post by Flagada
Hi all !
I am trying to animate a mesh deformation with quite a large number of
nodes (about 300000).
For now the best solution I have found is to make a list containing the
vtkpoints for each animation frame and loop by changing the vtkpoints of
the displayed polydata (or unstructuredgrid).
On a simple model without applying any color to the cells I can obtain an
animation rate of about 50fps wich is a good frame rate for me.
But if I apply colors with a PolyData.GetCellData().SetScalars() the
framerate goes down to 13fps.
Does anybody knows if it could be a better method to display mesh
animation or to improve the display rate of a mesh with colors ?
Here below is the python code I use.
It draws a disk of 800x400 nodes and if you press on F1 it animates a kind
of sinus wave.
First it calculate each frame, then it display the animation without color
and finally it display the animation with random color on cells.
Thanks !
############################
import vtk
import math
from time import time
import random
############################
# Creating disk mesh
disk = vtk.vtkDiskSource()
disk.SetInnerRadius(0.1)
disk.SetOuterRadius(2.0)
disk.SetRadialResolution(400)
disk.SetCircumferentialResolution(800)
disk.Update()
PolyData = disk.GetOutput()
print("%d nodes" % PolyData.GetNumberOfPoints())
print("%d elms" % PolyData.GetNumberOfCells())
# Setup actor and mapper
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(PolyData)
actor = vtk.vtkActor()
actor.SetMapper(mapper)
# Setup render window, renderer, interactor and camera
renderer = vtk.vtkRenderer()
renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)
renderWindowInteractor = vtk.vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)
style = vtk.vtkInteractorStyleTrackballCamera()
renderWindowInteractor.SetInteractorStyle(style)
camera = vtk.vtkCamera()
camera.Elevation(-45)
renderer.SetActiveCamera(camera)
#################################
# Calculate each frame and store the vtkPoints into vtkPointsList
PolyData = disk.GetOutput()
vtkPointsList = {}
print("Calculate...")
start_time = time()
vtkPointsList[ph] = vtk.vtkPoints()
vtkPointsList[ph].DeepCopy(PolyData.GetPoints())
NodePos = vtkPointsList[ph].GetPoint(i)
vtkPointsList[ph].SetPoint(i, NodePos[0], NodePos[1], 0.3 *
math.sin(NodePos[0] * 2 + ph * math.pi / 180))
PolyData.SetPoints(vtkPointsList[ph])
renderWindow.Render()
print("Done. Animate.")
# First animation without color
start_time = time()
PolyData.SetPoints(vtkPointsList[ph])
renderWindow.Render()
print("%.2f FPS" % (18 / (time() - start_time)))
# Activate cells colors
ELMcolors = vtk.vtkUnsignedCharArray()
ELMcolors.SetNumberOfComponents(3)
ELMcolors.SetName("Colors")
ELMcolors.InsertNextTuple([random.random() * 255, random.random()
* 255, random.random() * 255])
PolyData.GetCellData().SetScalars(ELMcolors)
# Second animation with color
start_time = time()
PolyData.SetPoints(vtkPointsList[ph])
renderWindow.Render()
print("%.2f FPS" % (18 / (time() - start_time)))
####################################
style.AddObserver("KeyPressEvent", KeyPress)
renderer.AddActor(actor)
renderWindow.Render()
renderer.ResetCamera()
renderWindowInteractor.Start()
############################
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--
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
101 East Weaver Street
Carrboro, North Carolina
27510 USA

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