.. meta::
    :description: Code snippets affine transform StructuredGrid

How to apply an affine transform to a StructuredGrid
====================================================

In this example we will apply an affine transform to different StructuredGrid.
StructuredGrid is an abstract class who has 3 concrete subclasses:
Channel, ROI and MultiROI.


Let's start by creating an instance of each of the StructuredGrid subclasses::

    from ORSModel import Channel
    from ORSModel import ROI, MultiROI, orsVect, orsColor
    channel = Channel()
    channel.setTitle('demo channel')
    #set it sizes, since we use the default voxel size, the channel is for now 100 meter cube
    channel.setXYZTSize(100,100,100,1)
    channel.setXSpacing(0.01)
    channel.setYSpacing(0.01)
    channel.setZSpacing(0.01)
    #now the channel is 1 meter cube
    #initilize it for float32 data
    channel.initializeDataForFLOAT()
    channelBox = channel.getBox()
    channelBox.grow(orsVect(-channelBox.getDirection0Size()*0.5, -channelBox.getDirection1Size()*0.5, -channelBox.getDirection2Size()*0.5))
    channel.paintBox(channelBox,  1, 0)
    channel.setDataDirty()
    #publish it so that it is visible in the Object properties list
    channel.publish()

    roiA = ROI()
    roiA.setTitle('roiA')
    roiA.copyShapeFromStructuredGrid(channel)
    roiA.setInitialColor(orsColor(1,0,0,1))
    roiA.paintSphere(roiA.getBox().getOrigin(), roiA.getBox().getDirection0Size(), 1, 0)
    roiA.publish()

    multiROIa= MultiROI()
    multiROIa.setTitle('multiROIa')
    multiROIa.copyShapeFromStructuredGrid(roiA)
    multiROIBox = multiROIa.getBox()
    multiROIa.setLabelCount(3)
    multiROIBox.grow(orsVect(-multiROIBox.getDirection0Size()*0.5, -multiROIBox.getDirection1Size()*0.5, -multiROIBox.getDirection2Size()*0.5))
    multiROIBox.setOrigin(multiROIa.getOrigin())
    multiROIa.paintBox(multiROIBox,  1, 0)

    multiROIBox.setOrigin(multiROIa.getBox().getCenter())
    multiROIa.paintBox(multiROIBox,  2, 0)

    multiROIBox.setOrigin((multiROIa.getBox().getOriginOpposite() - multiROIa.getBox().getOrigin())*0.25)
    multiROIa.paintBox(multiROIBox,  3, 0)
    multiROIa.publish()

Every StructuredGrid instance possesses a member variable of class Box. Box define a rectangular prism in space.
To apply an affine transform, you transform the Box of the StructuredGrid.
To define the affine transform, you use a Matrix4x4 object.

Let's define an affine transform::

    translation = Matrix4x4()
    translation.setTranslation(channel.getBox().getDirectionSizeVector()*0.25)
    rotationAxis = orsVect(0, 1, 0)
    rotation = Matrix4x4()
    rotation.setAsRotation(rotationAxis, 3.1416/8)
    scale = Matrix4x4()
    scale.setScale(orsVect(0.5,1,2))
    #now let's concatenate these transformation, in an arbritrary order
    fullTransform = scale*rotation*translation

Let's apply the affine transformation::

    channelT = channel.copy()
    channelT.setTitle('transformed channel')
    channelT.publish()
    box = channelT.getBox()
    box.transform(fullTransform)
    channelT.setBox(box)
    channelT.setGeometryDirty()

    #here we transform the original ROI and MultiROI
    roiA.setBox(box)
    multiROIa.setBox(box)
    roiA.setGeometryDirty()
    multiROIa.setGeometryDirty()