IsosurfaceLat

DESCRIPTION

This module calculates an isosurface of a scalar 3D lattice. An isosurface is a surface of constant value in a 3D scalar field. The algorithm used takes edge intersections and knits them into triangle meshes for rendering.

Vertex normals can be applied to the isosurface. Vertex normals are computed from the gradient of the scalar field if the Smooth parameter is on. If the Smooth parameter is off, no normals are applied. Inventor can generate normals when the geometry is rendered in this case.

On machines that do not have two-sided lighting, only one side of the isosurface will be properly lit. Lighting may be correct either on the side of the isosurface above the threshold, or on the side below the threshold. Flipping the normals will change the side that is correct.

If a lattice is wired into the Color Lattice port that lattice will be used to color the isosurface. The surface lattice and the color lattice need not be conforming. An optional colormap may be used to modulate a single channel from this lattice.

Coloring may be done smoothly, or with a texture map consisting of a number of distinct color bands. The texture map is generated by sampling the Colormap input when present. Otherwise a default set of colors is used. Texture maps may have 2, 4, 8, 16, 32, or 64 colors.

INPUTS

Port: Input
Type: Lattice
Constraints: 3-D

This is the lattice from which to extract an isosurface.

Port: Color Lattice
Type: Lattice
Optional: This port is optional.
Constraints: 3-D

This is an optional lattice to use to color the isosurface.

Port: Colormap
Type: Lattice
Optional: This port is optional.
Constraints: 1-D
Constraints: 4-vector
Constraints: float

This is an optional colormap which is used to map data values from a channel of the Color Lattice to colors, which are then applied to the surface.

WIDGETS

Port: Threshold
Type: Dial

This is the isosurface threshold value.

Port: Smooth?
Type: Check Box

s parameter selects between having no normals or generating vertex normals.

Port: Flip Normal?
Type: Check Box

This parameter reverses the normals applied to the isosurface to allow lighting either side of the isosurface on machines that do not support two-sided lighting.

Port: Color Variable
Type: Slider

This determines which of the data variables is used for coloring the surface. Only visible if the number of data variables in the Color Lattice is greater than 1.

Port: Surface Variable
Type: Slider

This determines which of the data variables is used for generating the surface. Only visible if the number of data variables of the surface lattice is greater than 1.

Port: Color Style
Type: Radio Box
Menu Item: Color Map
Menu Item: Texture Map

Controls the way in which colors are mapped onto the geometry.

In Color Map mode, each vertex is assigned a color according to its data value. The vertex colors are then interpolated between vertices and across faces to give continuous variation of color across the shape.

In Texture Map mode, the colors are assigned to regions of the geometry according to the range of data values at the vertices. This gives solid, distinct bands of color on the shape.

Port: Csize
Type: Slider

If texture mapping is used, the number of color bands is set to 2**n colors, where n is the value of the Csize widget. This widget is only visible when texture mapping is in force.

OUTPUTS

Port: Surface
Type: Geometry

Geometry of the returned shape.

KNOWN PROBLEMS

This module can produce surfaces with holes.

The texture mapped geometry can take longer to render on some architectures. Note that the default behaviour of the Render module is to switch off texturing when the viewpoint or geometry is changing.

SEE ALSO

LatToGeom, IsosurfacePyr


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