Mapper

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

Introduction

vtkMapper is an abstract class to specify interface between data and graphics primitives. Subclasses of vtkMapper map data through a lookuptable and control the creation of rendering primitives that interface to the graphics library. The mapping can be controlled by supplying a lookup table and specifying a scalar range to map data through.

There are several important control mechanisms affecting the behavior of this object. The ScalarVisibility flag controls whether scalar data (if any) controls the color of the associated actor(s) that refer to the mapper. The ScalarMode ivar is used to determine whether scalar point data or cell data is used to color the object. By default, point data scalars are used unless there are none, then cell scalars are used. Or you can explicitly control whether to use point or cell scalar data. Finally, the mapping of scalars through the lookup table varies depending on the setting of the ColorMode flag. See the documentation for the appropriate methods for an explanation.

Another important feature of this class is whether to use immediate mode rendering (ImmediateModeRenderingOn) or display list rendering (ImmediateModeRenderingOff). If display lists are used, a data structure is constructed (generally in the rendering library) which can then be rapidly traversed and rendered by the rendering library. The disadvantage of display lists is that they require additional memory which may affect the performance of the system.

Another important feature of the mapper is the ability to shift the Z-buffer to resolve coincident topology. For example, if you’d like to draw a mesh with some edges a different color, and the edges lie on the mesh, this feature can be useful to get nice looking lines. (See the ResolveCoincidentTopology-related methods.)

Methods

acquireInvertibleLookupTable

canUseTextureMapForColoring

Returns if we can use texture maps for scalar coloring. Note this doesn’t say we “will” use scalar coloring. It says, if we do use scalar coloring, we will use a texture. When rendering multiblock datasets, if any 2 blocks provide different lookup tables for the scalars, then also we cannot use textures. This case can be handled if required.

Argument	Type	Required	Description
scalars		Yes
cellFlag		Yes	True when the scalars are per cell instead of per point

clearColorArrays

Call to force a rebuild of color result arrays on next MapScalars. Necessary when using arrays in the case of multiblock data.

clearInvertibleColor

colorToValue

createDefaultLookupTable

Create default lookup table. Generally used to create one when none is available with the scalar data.

extend

Method used to decorate a given object (publicAPI+model) with vtkMapper 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	IMapperInitialValues	No	(default: {})

getAbstractScalars

Argument	Type	Required	Description
input		Yes
scalarMode	ScalarMode	Yes
arrayAccessMode		Yes
arrayId		Yes
arrayName		Yes

getAreScalarsMappedFromCells

When scalars are mapped from cells, there is one color coordinate per cell instead of one per point in the vtkDataArray getColorCoordinates(). It means that when getAreScalarsMappedFromCells() is true, the number of tuples in getColorCoordinates() is the number of points, and when getAreScalarsMappedFromCells() is false, the number of tuples in getColorCoordinates() is the number of cells.

getArrayAccessMode

getBounds

Get the bounds for this mapper as [xmin, xmax, ymin, ymax,zmin, zmax].

getColorByArrayName

Get the array name to color by.

getColorCoordinates

Provide read access to the color texture coordinate array

getColorMapColors

Provide read access to the color array.

getColorMode

Return the method of coloring scalar data.

getColorModeAsString

Return the method of coloring scalar data.

getColorTextureMap

Provide read access to the color texture array

getCustomShaderAttributes

getFieldDataTupleId

getInterpolateScalarsBeforeMapping

By default, vertex color is used to map colors to a surface. Colors are interpolated after being mapped. This option avoids color interpolation by using a one dimensional texture map for the colors.

getIsOpaque

Check if the mapper does not expect to have translucent geometry. This may happen when using ColorMode is set to not map scalars i.e. render the scalar array directly as colors and the scalar array has opacity i.e. alpha component. Default implementation simply returns true. Note that even if this method returns true, an actor may treat the geometry as translucent since a constant translucency is set on the property, for example.

getLookupTable

Get a lookup table for the mapper to use.

getNumberOfColorsInRange

The number of mapped colors in range

getPrimitiveCount

getScalarMode

Return the method for obtaining scalar data.

getScalarModeAsString

Return the method for obtaining scalar data.

getScalarRange

getScalarRangeByReference

getScalarVisibility

Check whether scalar data is used to color objects.

getStatic

Check whether the mapper’s data is static.

getUseLookupTableScalarRange

getViewSpecificProperties

mapScalars

Map the scalars (if there are any scalars and ScalarVisibility is on) through the lookup table, returning an unsigned char RGBA array. This is typically done as part of the rendering process. The alpha parameter allows the blending of the scalars with an additional alpha (typically which comes from a vtkActor, etc.) { rgba: Uint8Array(), location: 0/1/2, // Points/Cells/Fields }

Argument	Type	Required	Description
input		Yes
alpha	Number	Yes

newInstance

Method used to create a new instance of vtkMapper

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

setArrayAccessMode

Argument	Type	Required	Description
arrayAccessMode	Number	Yes

setColorByArrayName

Set the array name to color by.

Argument	Type	Required	Description
colorByArrayName	String	Yes

setColorMode

Argument	Type	Required	Description
colorMode	Number	Yes

setColorModeToDefault

Sets colorMode to DEFAULT

setColorModeToDirectScalars

Sets colorMode to DIRECT_SCALARS

setColorModeToMapScalars

Sets colorMode to MAP_SCALARS

setCustomShaderAttributes

Sets point data array names that will be transferred to the VBO

Argument	Type	Required	Description
customShaderAttributes	Array[String]	Yes

setFieldDataTupleId

When ScalarMode is set to UseFieldData, set the index of the tuple by which to color the entire data set. By default, the index is -1, which means to treat the field data array selected with SelectColorArray as having a scalar value for each cell. Indices of 0 or higher mean to use the tuple at the given index for coloring the entire data set.

Argument	Type	Required	Description
fieldDataTupleI	Number	Yes

setForceCompileOnly

Argument	Type	Required	Description
forceCompileOnly	Number	Yes

setInterpolateScalarsBeforeMapping

setLookupTable

Set a lookup table for the mapper to use.

setScalarMode

Control how the filter works with scalar point data and cell attribute data. By default (ScalarModeToDefault), the filter will use point data, and if no point data is available, then cell data is used. Alternatively you can explicitly set the filter to use point data (ScalarModeToUsePointData) or cell data (ScalarModeToUseCellData). You can also choose to get the scalars from an array in point field data (ScalarModeToUsePointFieldData) or cell field data (ScalarModeToUseCellFieldData). If scalars are coming from a field data array, you must call SelectColorArray before you call GetColors.

When ScalarMode is set to use Field Data (ScalarModeToFieldData), you must call SelectColorArray to choose the field data array to be used to color cells. In this mode, the default behavior is to treat the field data tuples as being associated with cells. If the poly data contains triangle strips, the array is expected to contain the cell data for each mini-cell formed by any triangle strips in the poly data as opposed to treating them as a single tuple that applies to the entire strip. This mode can also be used to color the entire poly data by a single color obtained by mapping the tuple at a given index in the field data array through the color map. Use SetFieldDataTupleId() to specify the tuple index.

Argument	Type	Required	Description
scalarMode		Yes

setScalarModeToDefault

Sets scalarMode to DEFAULT

setScalarModeToUseCellData

Sets scalarMode to USE_CELL_DATA

setScalarModeToUseCellFieldData

Sets scalarMode to USE_CELL_FIELD_DATA

setScalarModeToUseFieldData

Sets scalarMode to USE_FIELD_DATA

setScalarModeToUsePointData

Sets scalarMode to USE_POINT_DATA

setScalarModeToUsePointFieldData

Sets scalarMode to USE_POINT_FIELD_DATA

setScalarRange

Specify range in terms of scalar minimum and maximum (smin,smax). These values are used to map scalars into lookup table. Has no effect when UseLookupTableScalarRange is true.

Argument	Type	Required	Description
scalarRange		Yes

setScalarRange

Specify range in terms of scalar minimum and maximum (smin,smax). These values are used to map scalars into lookup table. Has no effect when UseLookupTableScalarRange is true.

Argument	Type	Required	Description
min		Yes
max		Yes

setScalarRangeFrom

Argument	Type	Required	Description
scalarRange		Yes

setScalarVisibility

Turn on/off flag to control whether scalar data is used to color objects.

Argument	Type	Required	Description
scalarVisibility	Boolean	Yes

setStatic

Turn on/off flag to control whether the mapper’s data is static. Static data means that the mapper does not propagate updates down the pipeline, greatly decreasing the time it takes to update many mappers. This should only be used if the data never changes.

Argument	Type	Required	Description
static	Boolean	Yes

setUseLookupTableScalarRange

Control whether the mapper sets the lookuptable range based on its own ScalarRange, or whether it will use the LookupTable ScalarRange regardless of it’s own setting. By default the Mapper is allowed to set the LookupTable range, but users who are sharing LookupTables between mappers/actors will probably wish to force the mapper to use the LookupTable unchanged.

Argument	Type	Required	Description
useLookupTableScalarRange	Boolean	Yes

setViewSpecificProperties

If you want to provide specific properties for rendering engines you can use viewSpecificProperties.

You can go and have a look in the rendering backend of your choice for details on specific properties. For example, for OpenGL/WebGL see OpenGL/PolyDataMapper/api.md If there is no details, viewSpecificProperties is not supported.

Argument	Type	Required	Description
viewSpecificProperties		Yes

useInvertibleColorFor

valueToColor