[vtkusers] Animation performance with cell color

[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.







On Sat, Nov 17, 2018 at 2:20 PM Flagada <flagada15 at gmail.com> wrote:

> 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()
>
> ############################
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-- 
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
101 East Weaver Street
Carrboro, North Carolina
27510 USA

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