Coordinate

Source (.js)Source (.d.ts)

Introduction

vtkCoordinate represents position in a variety of coordinate systems, and converts position to other coordinate systems. It also supports relative positioning, so you can create a cascade of vtkCoordinate objects (no loops please!) that refer to each other. The typical usage of this object is to set the coordinate system in which to represent a position (e.g., SetCoordinateSystemToNormalizedDisplay()), set the value of the coordinate (e.g., SetValue()), and then invoke the appropriate method to convert to another coordinate system (e.g., GetComputedWorldValue()).

The coordinate systems in vtk are as follows:

• DISPLAY - x-y pixel values in window 0, 0 is the lower left of the first pixel, size, size is the upper right of the last pixel
• NORMALIZED DISPLAY - x-y (0,1) normalized values 0, 0 is the lower left of the first pixel, 1, 1 is the upper right of the last pixel
• VIEWPORT - x-y pixel values in viewport 0, 0 is the lower left of the first pixel, size, size is the upper right of the last pixel
• NORMALIZED VIEWPORT - x-y (0,1) normalized value in viewport 0, 0 is the lower left of the first pixel, 1, 1 is the upper right of the last pixel
• VIEW - x-y-z (-1,1) values in pose coordinates. (z is depth)
• POSE - world coords translated and rotated to the camera position and view direction
• STABILIZED - used by rendering backends to deal with floating point resolution issues. Similar to world coordinates but with a translation to try to get the matricies to be well behaved.
• WORLD - x-y-z global coordinate values
• MODEL - x-y-z coordinate values in the data's coordinates, the actor holds a matrix to go to world
• BUFFER - x-y-x coordinates as stored int he VBO
• DATA - x-y-z the original coordintes of the dataset
• USERDEFINED - x-y-z in User defined space

If you cascade vtkCoordinate objects, you refer to another vtkCoordinate object which in turn can refer to others, and so on. This allows you to create composite groups of things like vtkActor2D that are positioned relative to one another.

!!! note In cascaded sequences, each vtkCoordinate object may be specified in different coordinate systems!

How the data may go from a dataset through the rendering pipeline in steps

Dataset -> GPU buffer: DCBCMatrix usually this is just a shift and/or scale to get the GPU buffer for the points into values that will nto run into floating point resolution issues. This is handled when creating the buffer

• Buffer to Model: BCMCMatrix just reverses the shift/scale applied to the buffer above
• Model to World: MCWCMatrix uses the Actor's matrix to transform the points to World coordinates
• World to Stabilized: WCSCMatrix Maps world to the shifted maybe scalede renderer's stabilized center/matrix
• Stabilized to View: SCVCMatrix captures the rest of the transformation to View coordinates
• View to Projection: VCPCMatrix cpatures the ortho/perspective matrix
• Projection to ...: done by the GPU hardware as part of the vertex to fragment

Typically the process is simplified into the 4 following steps :

• DataSet to Buffer - done when creating the buffer
• Buffer To Stabilized - BCSCMatrix done in the vertex shader, part of the mapperUBO
• Stabilized To Projection - SCPCMatrix second matrix mult done in the vertex shader, part of the rendererUBO
• Projection to ...: vertex to fragment shader operations

See Also

vtkActor2D

Methods

extend

Method use to decorate a given object (publicAPI+model) with vtkCoordinate characteristics.

Argument	Type	Required	Description
publicAPI		Yes	object on which methods will be bounds (public)
model		Yes	object on which data structure will be bounds (protected)
initialValues	ICoordinateInitialValues	No	(default: {})

getComputedDisplayValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getComputedDoubleDisplayValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getComputedDoubleViewportValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getComputedLocalDisplayValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getComputedValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getComputedViewportValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getComputedWorldValue

Argument	Type	Required	Description
ren	vtkRenderer	Yes	The vtkRenderer instance.

getCoordinateSystem

Get the coordinate system which this coordinate is defined in. The options are Display, Normalized Display, Viewport, Normalized Viewport, View, and World.

getCoordinateSystemAsString

Get the coordinate system which this coordinate is defined in as string.

getReferenceCoordinate

getRenderer

Get mapper that was picked (if any)

getValue

Get the value of this coordinate.

newInstance

Method use to create a new instance of vtkCoordinate

Argument	Type	Required	Description
initialValues	ICoordinateInitialValues	No	for pre-setting some of its content

setCoordinateSystem

Set the coordinate system which this coordinate is defined in. The options are Display, Normalized Display, Viewport, Normalized Viewport, View, and World.

Argument	Type	Required	Description
coordinateSystem	Coordinate	Yes

setCoordinateSystemToDisplay

Set the coordinate system to Coordinate.DISPLAY

setCoordinateSystemToNormalizedDisplay

Set the coordinate system to Coordinate.NORMALIZED_DISPLAY

setCoordinateSystemToNormalizedViewport

Set the coordinate system to Coordinate.NORMALIZED_VIEWPORT

setCoordinateSystemToProjection

Set the coordinate system to Coordinate.PROJECTION

setCoordinateSystemToView

Set the coordinate system to Coordinate.VIEW

setCoordinateSystemToViewport

Set the coordinate system to Coordinate.VIEWPORT

setCoordinateSystemToWorld

Set the coordinate system to Coordinate.WORLD

setProperty

Argument	Type	Required	Description
property	vtkProperty	Yes

setReferenceCoordinate

Argument	Type	Required	Description
referenceCoordinate	vtkCoordinate	Yes

setRenderer

Argument	Type	Required	Description
renderer	vtkRenderer	Yes

setValue

Set the value of this coordinate.

Argument	Type	Required	Description
value		Yes