volume_render

Synopsis

directly render a volume

Input Port

in_mesh

Mesh_Unif+Dim3+Space3+Scalar

Parameters

Output Port

obj	DefaultObject

Description

volume_render directly renders a uniform, 3D, 3-space, scalar, byte volume using either the BTF or Ray-tracer volume rendering modes. The Ray-tracer volume mode, which is configured as the default, is available only in the software renderer. The BTF volume mode is available only in the software renderer. In both cases, when the volume modes are available, mixed rendering of volumes and geometries is supported.

This module is provided as a convenient way to access user interface controls via the Module Panel user interface container for the Graphics Display kit surface and volume modes and the datamap's alpha component. These controls provide quick access to the most commonly used attributes that control the volume_render module.

The volume_render module is also configured with an alternate object whose visibility is disabled. When any object in the view's hierarchy is directly manipulated, the volume will not be rendered.

Input

inx

in

The input field. The input field should be 3D, 3-space, uniform, with byte or short node data in order for it to be volume rendered.

Parameters

Surface

UIoptionMenu. This parameter controls the lighting and interpolation performed by the volume rendering technique that has been chosen.

Inherit means that the surface rendering mode is inherited from a parent Graphics Display Kit object. None means that no volume rendering is done.

When the volume mode selected is Ray-tracer, No lighting means that no lighting and no interpolation are done. Flat means that lighting is done but no interpolation is done. Gouraud means that lighting and interpolation are done. These options produce progressively higher quality renderings. The higher quality modes also take longer to render.

When the volume mode selected is BTF, lighting is never applied. No lighting and flat cause point sampling to be done. Gouraud causes bi-linear interpolation to be done.

Volume

UIoptionMenu. This parameter controls the volume rendering mode.

Inherit means that the volume rendering mode is inherited from a parent Graphics Display Kit object. None means that no volume rendering is done. BTF means that a back-to-front volume rendering technique is used. This technique is available only in the OpenGL renderer. Ray-tracer means that a ray-tracing volume rendering technique is used. This technique is available only in the software renderer.

Interpolation

UIoptionMenu. The parameter controls the volume rendering interpolation method; that is, how voxel values are mapped to rays or pixels.

Option	Meaning
Point	The value of the nearest voxel is used.
Trilinear	Values are linearly interpolated fro the two nearest voxels in each of the 3 principal directions.
in_mesh	Mesh_Unif+Dim3+Space3+Scalar

ray_algorithm

UIoptionMenu. The parameter controls how data or spatial values are mapped to the ray and how the ray values are mapped to the final color for the pixel.

Option	Meaning
Direct Composite	At each step along the ray, the interpolated value is composited with the current value using standard alpha blending equations.
Average Value	The ray maintains a moving average of the voxel values along its length.
Maximum Value	The ray maintains the maximum value encountered along its length.
Distance to Max	The ray maintains a distance measure and the maximum value. The distance is updated only when a new maximum value is found.
SFP	Simulated Fluorescence Process algorithm. This algorithm is described in: H.T.M. van der Voort et al., Journal Microscopy, Vol. 153(2), 123-132 (1989)

distance normalize

The parameter controls how the ray ranges are normalized when the ray algorithm is Distance to Max:

Value	Meaning
Global	The ray ranges are normalized to the diameter of a sphere enclosing the entire volume.
View	The ray ranges are normalized to the depth of the current view. This depth is the maximum extent of the data volume projected onto the viewing direction.
Ray	The ray range is individually normalized to the length of the ray

fat_ray

This parameter enables a super-sampling method that traces a single ray through a 4x4 block of pixels. The resulting image is faster to render, but of lower resolution.

SFP Absorption

This parameter controls the absorption of the exciting radiation when the ray algorithm is SFP.

SFP Emission

This parameter controls the emmittance of fluorescence radiation in the direction of the observer when the ray algorithm is SFP.

Datamap Minimum

Datamap Maximum

UIslider. These parameters control the minimum and maximum data range of the entire current datamap. In most datamaps the minimum and maximum data range is automatically set taken from the minimum and maximum of the input fields's node data. In Volume rendering datamaps however, the minimum and maximum are set according to the input data type.

Range Control Point

UIslider. This parameter allows the midpoint of the two ranges to be altered. By default, the first range in the datamap spans from the minimum data value to the midpoint. The second range in the datamap spans from the midpoint to the maximum data value. When the Range Alpha toggle is set, this parameter allows you to move the midpoint.

Current Range

UIslider. The parameter selects the range in the datamap whose alpha component is to be edited. The volume render module has a datamap with two ranges by default.

Alpha Range Model

UIoptionMenu. This parameter controls the type of alpha range model for the current data range. Valid range models are linear and step. When linear is selected, the alpha component is interpolated between the minimum and maximum values specified for the current data range. When step is selected, the minimum alpha value is used for the filrst half of the data range and the macimum alpha value is used for the second half of the data range.

Minimum Alpha
Maximum Alpha

UIslider. These parameters allow you to control the minimum and maximum alpha values for the current data range.

Output Port

obj

Graphics Display Kit DefaultObject. This is a renderable object that can be connected directly to one of the Graphics Display Kit's viewers.

Example

Libraries.Examples.Visualization.VolumeRendSurface

v/dv_examp/vol_rend.v

Shows the default settings of the volume_render macro. The default settings emphasize the surface finding abilities of the

AVS/Express raycasting volume renderer. The first datamap range has an alpha of 0.0 (completely transparent), while the second datamap range has

an alpha of 1.0 (completely opaque). Thus the visualization shows the surface found at the transistion ("control point") between the

two ranges. The net effect is similar to a surface-oriented visualization technique such as isosurface.

Libraries.Examples.Visualization.VolumeRendHiQual

v/dv_examp/vol_rend2.v

Similar to VolumeRendSurface, but with the fat ray parameter turned off. Gives higher quaility results at the expense of more computation

time.

Libraries.Examples.Visualization.VolumeRendTransparent

v/dv_examp/vol_rend3.v

The dataset is the same as with the examples that show surface finding, but the datamap alpha values are set to produce a volume-oriented

visualization. Most of the dataset's data values are mapped to a partially transparent color value, enabling you to "see through" the

object. Note that the turning off fat ray is not as important for visual quaility when you are not trying to precisely locate a surface.

Libraries.Examples.Visualization.VolumeRendSFP

v/dv_examp/vol_rend4.v

Shows the use of the Simulated Fluorescence Process algorithm. The sample uses a single-range grey-scale datamap. Note that the

alpha settings are not used by the SFP algorithm.

File

v/modules.v

See also related modules

Not applicable.