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GTS Library Reference Manual
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Isosurfaces from 3D functions

Name

Isosurfaces from 3D functions -- computing triangulated isosurfaces of a given function f(x,y,z).

Synopsis


#include <gts.h>


struct      GtsCartesianGrid;
struct      GtsGridPlane;

GtsGridPlane* gts_grid_plane_new            (guint nx,
                                             guint ny);
void        gts_grid_plane_destroy          (GtsGridPlane *g);

struct      GtsIsoSlice;

GtsIsoSlice* gts_iso_slice_new              (guint nx,
                                             guint ny);
void        gts_iso_slice_fill              (GtsIsoSlice *slice,
                                             GtsGridPlane *plane1,
                                             GtsGridPlane *plane2,
                                             gdouble **f1,
                                             gdouble **f2,
                                             gdouble iso,
                                             GtsVertexClass *klass);
void        gts_iso_slice_fill_cartesian    (GtsIsoSlice *slice,
                                             GtsCartesianGrid g,
                                             gdouble **f1,
                                             gdouble **f2,
                                             gdouble iso,
                                             GtsVertexClass *klass);
void        gts_iso_slice_destroy           (GtsIsoSlice *slice);
void        gts_isosurface_slice            (GtsIsoSlice *slice1,
                                             GtsIsoSlice *slice2,
                                             GtsSurface *surface);
void        (*GtsIsoCartesianFunc)          (gdouble **a,
                                             GtsCartesianGrid g,
                                             guint i,
                                             gpointer data);
void        gts_isosurface_cartesian        (GtsSurface *surface,
                                             GtsCartesianGrid g,
                                             GtsIsoCartesianFunc f,
                                             gpointer data,
                                             gdouble iso);
void        gts_isosurface_tetra            (GtsSurface *surface,
                                             GtsCartesianGrid g,
                                             GtsIsoCartesianFunc f,
                                             gpointer data,
                                             gdouble iso);
void        gts_isosurface_tetra_bounded    (GtsSurface *surface,
                                             GtsCartesianGrid g,
                                             GtsIsoCartesianFunc f,
                                             gpointer data,
                                             gdouble iso);

Description

Using the gts_isosurface_cartesian() function, it is possible to build a triangulated isosurface of a given user-defined function. As its name indicates this function assumes that the values of the user-defined function are defined for points located on a regular cartesian grid described by the GtsCartesianGrid parameter. The triangles describing the isosurface are computed for each pair of successive planes z and z+dz in a pipelined manner. Consequently only two planes need to be stored in memory at any time. This allows to construct isosurfaces for datasets too large to fit in main memory.

Details

struct GtsCartesianGrid

struct GtsCartesianGrid {
  guint nx, ny, nz;
  gdouble x, dx, y, dy, z, dz;
};

A regular cartesian grid is defined by the number of points in each direction, the spatial increment in each direction and the coordinates of the first point.

guint nxNumber of points in direction x.
guint nyNumber of points in direction y.
guint nzNumber of points in direction z.
gdouble xx coordinate of the first point.
gdouble dxIncrement in direction x.
gdouble yy coordinate of the first point.
gdouble dyIncrement in direction y.
gdouble zz coordinate of the first point.
gdouble dzIncrement in direction z.

struct GtsGridPlane

struct GtsGridPlane {
  GtsPoint ** p;
  guint nx, ny;
};

gts_grid_plane_new ()

GtsGridPlane* gts_grid_plane_new            (guint nx,
                                             guint ny);

nx : 
ny : 
Returns : 

gts_grid_plane_destroy ()

void        gts_grid_plane_destroy          (GtsGridPlane *g);

g : 

struct GtsIsoSlice

struct GtsIsoSlice;

A GtsIsoSlice is an opaque data structure containing the coordinates of the points located on the isosurface for a given slice of the user-defined function.

gts_iso_slice_new ()

GtsIsoSlice* gts_iso_slice_new              (guint nx,
                                             guint ny);

nx : number of vertices in the x direction.
ny : number of vertices in the y direction.
Returns : a new GtsIsoSlice.

gts_iso_slice_fill ()

void        gts_iso_slice_fill              (GtsIsoSlice *slice,
                                             GtsGridPlane *plane1,
                                             GtsGridPlane *plane2,
                                             gdouble **f1,
                                             gdouble **f2,
                                             gdouble iso,
                                             GtsVertexClass *klass);

Fill slice with the coordinates of the vertices defined by f1 (x,y,z) = iso and f2 (x, y, z) = iso.

slice : a GtsIsoSlice.
plane1 : a GtsGridPlane.
plane2 : another GtsGridPlane.
f1 : values of the function corresponding to plane1.
f2 : values of the function corresponding to plane2.
iso : isosurface value.
klass : a GtsVertexClass or one of its descendant to be used for the new vertices.

gts_iso_slice_fill_cartesian ()

void        gts_iso_slice_fill_cartesian    (GtsIsoSlice *slice,
                                             GtsCartesianGrid g,
                                             gdouble **f1,
                                             gdouble **f2,
                                             gdouble iso,
                                             GtsVertexClass *klass);

Fill slice with the coordinates of the vertices defined by f1 (x,y,z) = iso and f2 (x, y, z) = iso.

slice : a GtsIsoSlice.
g : a GtsCartesianGrid.
f1 : values of the function for plane z = g.z.
f2 : values of the function for plane z = g.z + g.dz.
iso : isosurface value.
klass : a GtsVertexClass.

gts_iso_slice_destroy ()

void        gts_iso_slice_destroy           (GtsIsoSlice *slice);

Free all memory allocated for slice.

slice : a GtsIsoSlice.

gts_isosurface_slice ()

void        gts_isosurface_slice            (GtsIsoSlice *slice1,
                                             GtsIsoSlice *slice2,
                                             GtsSurface *surface);

Given two successive slices slice1 and slice2 link their vertices with segments and triangles which are added to surface.

slice1 : a GtsIsoSlice.
slice2 : another GtsIsoSlice.
surface : a GtsSurface.

GtsIsoCartesianFunc ()

void        (*GtsIsoCartesianFunc)          (gdouble **a,
                                             GtsCartesianGrid g,
                                             guint i,
                                             gpointer data);

This user-defined function is passed to the gts_isosurface_cartesian() function. Given a particular GtsCartesianGrid g it must fill the array a with the values of the function for the plane z=g.z (or for the corresponding index i). This function is always called in order by gts_isosurface_cartesian(), i.e. i varies from 0 to g.nz - 1 with an increment of one (and similarly g.z is incremented every time by g.dz).

a :the 2D array to be filled.
g :a GtsCartesianGrid.
i :the z direction index of the plane to be filled.
data :user data.

gts_isosurface_cartesian ()

void        gts_isosurface_cartesian        (GtsSurface *surface,
                                             GtsCartesianGrid g,
                                             GtsIsoCartesianFunc f,
                                             gpointer data,
                                             gdouble iso);

Adds to surface new faces defining the isosurface f(x,y,z) = iso. By convention, the normals to the surface are pointing toward the positive values of f(x,y,z) - iso.

The user function f is called successively for each value of the z coordinate defined by g. It must fill the corresponding (x,y) plane with the values of the function for which the isosurface is to be computed.

surface : a GtsSurface.
g : a GtsCartesianGrid.
f : a GtsIsoCartesianFunc.
data : user data to be passed to f.
iso : isosurface value.

gts_isosurface_tetra ()

void        gts_isosurface_tetra            (GtsSurface *surface,
                                             GtsCartesianGrid g,
                                             GtsIsoCartesianFunc f,
                                             gpointer data,
                                             gdouble iso);

Adds to surface new faces defining the isosurface f(x,y,z) = iso. By convention, the normals to the surface are pointing toward the positive values of f(x,y,z) - iso.

The user function f is called successively for each value of the z coordinate defined by g. It must fill the corresponding (x,y) plane with the values of the function for which the isosurface is to be computed.

surface : a GtsSurface.
g : a GtsCartesianGrid.
f : a GtsIsoCartesianFunc.
data : user data to be passed to f.
iso : isosurface value.

gts_isosurface_tetra_bounded ()

void        gts_isosurface_tetra_bounded    (GtsSurface *surface,
                                             GtsCartesianGrid g,
                                             GtsIsoCartesianFunc f,
                                             gpointer data,
                                             gdouble iso);

Adds to surface new faces defining the isosurface f(x,y,z) = iso. By convention, the normals to the surface are pointing toward the positive values of f(x,y,z) - iso. To ensure a closed object, a boundary of G_MINDOUBLE is added around the domain

The user function f is called successively for each value of the z coordinate defined by g. It must fill the corresponding (x,y) plane with the values of the function for which the isosurface is to be computed.

surface : a GtsSurface.
g : a GtsCartesianGrid.
f : a GtsIsoCartesianFunc.
data : user data to be passed to f.
iso : isosurface value.



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