Lecture 5

Fundamental Algorithms (1 of 2)

(includes text and images from the 3rd edition of the VTK book)

Cells specify topology while points specify geometry

Types of Datasets (each of these has their own class in vtk) - a dataset has an organizing structure and a set of associated attribute data

Project 1 will start out with unstructured points and Project 2 will start out with image data, though in both cases the data may go through several forms depending on how it will be eventually be visualized


Linear Cells - linear or constant interpolation functions

eg for the Hexahedron we can declare a cell to be a hexahedron and then give the connectivity list of point IDs (0, 1, 2, 3, 4, 5, 6, 7) where the point IDs in the connectivity list index into a (potentailly much larger) point coordinate list of x,y,z point locations. We know implicitely that 0,1 is one of the 12 edges and 0, 1, 2, 3 is one of the six faces.

Nonlinear Cells

    more accurate rate interpolation functions
    model curved geometry better

linear cells are easily converted to linear graphics primitives. nonlinear cells (except maybe for NURBS) must first be converted (tesselated) into linear form

Attribute Data - each Cell has 0 or more pieces of attribute data associated with it.

Fundamental Algorithms (Chap 6 vtk)

Categorize algorithms according to:



Scalar Algorithms

single data value associated with each point in dataset

Flow density coloured with different lookup tables

Some contours from last time - the grand canyon - 2D contours and Iron Protein - 3D contours

Vector Algorithms

Three different representations of venctor data: hedgehog, glyphs, streamlines


displacement plot

and we previously looked at the grand canyon height map represented as a 2D texture which we warped on one axis into a 3D form and coloured based on its elevation

carotid.vtk from the textbook with 167,000 3D vectors shown as arrows, cones, and lines

carotid arrows

carotid cones

carotid lines

kithen.vtk from the textbook

first with glyphs - with complicated flow patterns it can be hard to see the flow from discrete vectors

kitchen.vtk with glyphs

and then with 2 sets of streamtracers which integrate through the discrete vectors to show streams flowing from, to, or through a given set of points

kitchen.vtk with streamtracer

and streamlines starting from a particular area, with contextual polygonal information

Coming Next Time

More Fundamental Algorithms

last revision 1/21/11