Generate point cloud from depth map image using vtk

Question

I wrote a code in python to generate a depth map of a 3D model and save it as an image using VTK.
But when I wrote code to generate the point cloud from the image, only part of the point cloud was generated. I can't find the reason. I use the same camera parameter in the two code. code and 3d model

Generate Depth map image from mesh

import vtk
import os
import numpy as np
from vtk.util import numpy_support


reader = vtk.vtkXMLPolyDataReader()
data_path = 'C:/Users/jiang/Repository/ModelNet10/chair_train_scaled'
path = os.path.join(data_path, "chair_0001.vtp") #Archive path
reader.SetFileName(path)
reader.Update()

ren = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

bounds = reader.GetOutput().GetBounds()

voxelModeller = vtk.vtkVoxelModeller ()
voxelModeller.SetSampleDimensions(128,128,128)
voxelModeller.SetModelBounds(bounds)
voxelModeller.SetMaximumDistance(0.1)
voxelModeller.SetScalarTypeToFloat()

voxelModeller.SetInputConnection(reader.GetOutputPort())
voxelModeller.Update()

# Create transfer mapping scalar value to opacity
opacityTransferFunction = vtk.vtkPiecewiseFunction()
opacityTransferFunction.AddPoint(0, 0.0)
opacityTransferFunction.AddPoint(1, 1)

# Create transfer mapping scalar value to color
colorTransferFunction = vtk.vtkColorTransferFunction()
colorTransferFunction.AddRGBPoint(0.0, 1.0, 1.0, 1.0)
colorTransferFunction.AddRGBPoint(1.0, 1.0, 0.0, 0.0)

# The property describes how the data will look
volumeProperty = vtk.vtkVolumeProperty()
volumeProperty.SetColor(colorTransferFunction)
volumeProperty.SetScalarOpacity(opacityTransferFunction)
volumeProperty.ShadeOn()
volumeProperty.SetInterpolationTypeToLinear()

# The mapper / ray cast function know how to render the data
volumeMapper = vtk.vtkGPUVolumeRayCastMapper()
volumeMapper.SetBlendModeToComposite()
volumeMapper.SetInputConnection(voxelModeller.GetOutputPort())
volumeMapper.RenderToImageOn()
# The volume holds the mapper and the property and
# can be used to position/orient the volume
volume = vtk.vtkVolume()
volume.SetMapper(volumeMapper)
volume.SetProperty(volumeProperty)


ren.AddVolume(volume)
ren.SetBackground(1, 1, 1)
renWin.SetSize(128, 128)


ren.GetActiveCamera().SetPosition(32, 0,0)
ren.GetActiveCamera().SetFocalPoint(0, 0, 0)
ren.GetActiveCamera().SetViewUp(0, 0, 1)
ren.GetActiveCamera().SetClippingRange(20,50)
renWin.Render()

dpimg = vtk.vtkImageData()
volumeMapper.GetDepthImage(dpimg)

scale = vtk.vtkImageShiftScale()
scale.SetOutputScalarTypeToUnsignedChar()

scale.SetInputData(dpimg)
scale.SetShift(0)
scale.SetScale(255)


imageWriter = vtk.vtkBMPWriter()
imageWriter.SetFileName("depthmap1.bmp")
imageWriter.SetInputConnection(scale.GetOutputPort())
imageWriter.Write()

Generate cloud points from depth map image

import vtk
import os
import numpy as np
from vtk.util import numpy_support

reader = vtk.vtkBMPReader()
reader.SetFileName('depthmap3.bmp')
reader.Update()
dpscalar = reader.GetOutput().GetPointData().GetScalars()
dpnp1d = numpy_support.vtk_to_numpy(dpscalar)
print(np.max(dpnp1d),np.min(dpnp1d))

scale = vtk.vtkImageShiftScale()
scale.SetOutputScalarTypeToFloat()
#scale.SetInputConnection(filter.GetOutputPort())
scale.SetInputConnection(reader.GetOutputPort())
scale.SetShift(0)
#scale.SetScale(-1/255.0)
scale.SetScale(1/255.0)
scale.Update()

dpscalar = scale.GetOutput().GetPointData().GetScalars()
dpnp1d = numpy_support.vtk_to_numpy(dpscalar)
print(np.max(dpnp1d),np.min(dpnp1d))


ren = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
ren.SetBackground(1, 1, 1)
renWin.SetSize(300,300)
renWin.AddRenderer(ren)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)


camera =ren.GetActiveCamera()
camera.SetPosition(-32, 0,0)
camera.SetFocalPoint(0, 0, 0)
camera.SetViewUp(0, 0, 1)
camera.SetClippingRange(20,50)
axial = vtk.vtkMatrix4x4()
axial.DeepCopy((3.73205, 0, 0, 0,
                 0, 3.73205, 0, 0,
                 0, 0, -2.33333, -66.6667,
                 0, 0, -1, 0)) 
#camera.SetUseExplicitProjectionTransformMatrix(True)
#camera.SetExplicitProjectionTransformMatrix(axial)
print(camera)

print(camera.GetWindowCenter ())

pc = vtk.vtkDepthImageToPointCloud()
pc.SetInputConnection(scale.GetOutputPort())
pc.SetCamera(camera)
pc.CullNearPointsOn()
pc.CullFarPointsOn()
#pc.ProduceVertexCellArrayOff()
pc.Update()
print(pc)
#print(ren.GetActiveCamera())

pcMapper = vtk.vtkPolyDataMapper()
pcMapper.SetInputConnection(pc.GetOutputPort())

# pcMapper = vtk.vtkPointGaussianMapper()
# pcMapper.SetInputConnection(pc.GetOutputPort())
# pcMapper.EmissiveOff()
# pcMapper.SetScaleFactor(0.0)

pcActor = vtk.vtkActor()
pcActor.SetMapper(pcMapper)
iren.Initialize()
ren.AddActor(pcActor)
ren.SetBackground(0,0,0)
# ren.GetActiveCamera().SetPosition(32, 0,0)
# ren.GetActiveCamera().SetFocalPoint(0, 0, 0)
# ren.GetActiveCamera().SetViewUp(0, 0, 1)
ren.ResetCamera()
renWin.Render()
iren.Start()

Peng Jiang Peng Jiang · Accepted Answer · 2018-10-20T00:50:51

I figure out the problem. When I use the vtkBMPReader, the output of this class is a 3 channel vtkImageData, but the vtkDepthImageToPointCloud only receive a 1 channel depth image. So We need to use vtkImageExtractComponents to get the first channel of the vtkBMPReader output.

But I still don't understand how vtk compute projection transform matrix.

Generate point cloud from depth map image using vtk

2 Answers