Scalar Field Visualization¶

This module provides visualization of artificial 3D shapes for data (e.g. scalar field) visualization.

Input data may be provided as as discrete set of points that shall be encosed by the shape.

For example:

import _ossimPlanet
import _surface

globe = _ossimPlanet.ossimPlanet()
# ... globe initialization

surface = _surface.surface(globe)
point = [
  (0,0,0), (1,0,0), (0,1,0), (0,0,1),
  (2,2,2), (3,2,2), (2,3,2), (2,2,3)]
surface.addAlphaShape(points, 0, (1, 0, 0, 0.7))

while not globe.renderDone():
    globe.renderFrame()

Alternatively, the input data may be provided as a continuous surphace function f(x,y,z).

For example:

import _ossimPlanet
import _surface

globe = _ossimPlanet.ossimPlanet()
# ... globe initialization

surface = _surface.surface(globe)
surface.addSurface(lambda x,y,z: x*x+y*y+z*z - 0.2, (1, 0, 0, 0.7))

while not globe.renderDone():
    globe.renderFrame()

Class surface¶

class surface¶: The surface provides 3D shape visualization based on CGAL library functions.

surface instances have the following methods:

surface.setLocation(latitude, longitude, height)¶

The setLocation() method configures location of the center of the shape.

The latitude and longitude parameters are measured in the geodetic coordinates. The height is measured above terrain (AGL).

By default, the shape is located at zero coordinates and zero height.

surface.setScale(scale)¶

The setScale() method configures scale of the shape.

By default, the shape is not scaled (1.0).

surface.addSurface(function, color)¶

The addSurface() method inserts new artificial surface that is determined by a surface function and a color.

The user provided surface function f(x,y,z) takes point coordinates and determines if the point is inside, or outside the shape. For a given (x,y,z)

the f(x,y,z) return value < 0.0, if the point is inside the shape;

the f(x,y,z) return value > 0.0, if the point is outside the shape.

For example, the following function determines a sphere of diameter 1.0:

lambda x,y,z: x*x+y*y+z*z - 1.0

The color parameter is a 4-tuple (red, green, blue, alpha). The alpha value determines transparency of the shape.

surface.addAlphaShape(points, count, color)¶

The addAlphaShape() method inserts new artificial surface that is constructed as a convex hull enclosing the given list of data points. Each data point in the list is a 3-tuple (x,y,z) determining cartesian coordinates of the point.

Alpha shape is a generalization of a convex hull, parametrized by alpha. The alpha value can be interpreted as a maximal distance of neighbouring points. The alpha shape thus becomes convex hull for infinite alpha.

There is no alpha parameter. This function calculates optimal alpha value to get the given count of solid components.

count == 1, creates a single solid component enclosing all given data points;

count > 1, creates the requested count of solid components;

count == 0 (special case), creates the optimal number of components, i.e. one or more, depending on the given data points.

The color parameter is a 4-tuple (red, green, blue, alpha). The alpha value determines transparency of the shape.

Note: There is a terminology clash. The shape parameter alpha is nohow related to the color alpha value.