SPHERE_XYZ_DISPLAY_OPENGL
Display Unit Sphere and 3D Points Using OpenGL

SPHERE_XYZ_DISPLAY_OPENGL is a C++ program which reads the name of a data file containing a list of 3D point coordinates, reads the data, and displays a unit sphere and the points using OPENGL.

It can be difficult to visualize a set of points that lie on the unit sphere. You can't see the curving surface, and you can see points that should not be visible, because they are on the other side of the sphere. By starting the display with a unit sphere, and then adding the 3D points you want to see, both of these problems are resolved. The addition of the sphere gives important visual cues as to how to "read" the data.

The program displays the data, and slowly rotates it. Clicking the mouse stops the rotation; another click starts it again, with rotation around a different axis.

Usage:

sphere_xyz_display_opengl data.txt

• data.txt is a file containing a list of the XYZ coordinates of the points to plot.

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

SPHERE_XYZ_DISPLAY_OPENGL is available in a C++ version.

Related Data and Programs:

FERN_OPENGL, a C++ program which uses OpenGL to display the Barnsley fractal fern.

SPHERE_XYZ_DISPLAY, a MATLAB program which reads XYZ information defining points in 3D, and displays a unit sphere and the points in the MATLAB graphics window.

XY_DISPLAY_OPENGL, a C++ program which reads an XY file of 2D point coordinates, and displays an image of those points using OpenGL.

XYZ, a data directory which contains some examples of 3D pointsets.

XYZ_DISPLAY_OPENGL, a C++ program which reads XYZ information defining points in 3D, and displays an image using OpenGL.

XYZF_DISPLAY_OPENGL, a C++ program which reads XYZF information defining points and faces in 3D, and displays an image using OpenGL.

XYZL_DISPLAY_OPENGL, a C++ program which reads XYZL information defining points and lines in 3D, and displays an image using OpenGL.

Reference:

1. Edward Angel,
   Interactive Computer Graphics, a Top-Down Approach with OpenGL,
   Addison-Wesley, 2000,
   ISBN: 0-201-38597-X,
   LC: T385.A514.
2. Renate Kempf, Chris Frazier, editors,
   OpenGL Reference Manual,
   Fourth Edition,
   Addison-Wesley, 2004,
   ISBN: 032117383X,
   LC: T385.O642
3. Mason Woo, Jackie Neider, Tom Davis,
   OpenGL Programming Guide,
   Addison-Wesley, 1997,
   ISBN: 0-201-46138-2,
   LC: T385.N435
4. Richard Wright, Michael Sweet,
   OpenGL Superbible,
   Third Edition,
   Sams, 2004,
   ISBN: 0672326019,
   LC: T385.W73
5. http://www.opengl.org/
   The official OpenGL site.

Source Code:

• sphere_xyz_display_opengl.cpp, the source code.
• sphere_xyz_display_opengl.sh, commands to compile the source code.

Examples and Tests:

• uniform_on_sphere01_triangle.xyz, points selected uniformly at random from a spherical triangle.
• uniform_on_sphere01_triangle.png, a PNG image of the screen generated by Open GL.

List of Routines:

• MAIN is the main program for SPHERE_XYZ_DISPLAY_OPENGL.
• CH_EQI is true if two characters are equal, disregarding case.
• CH_TO_DIGIT returns the integer value of a base 10 digit.
• DISPLAY generates the graphics output.
• MOUSE determines the response to mouse input.
• MYINIT initializes OpenGL state variables dealing with viewing and attributes.
• MYRESHAPE determines the window mapping.
• R8_MAX returns the maximum of two R8's.
• R8_MIN returns the minimum of two R8's.
• R83VEC_MAX returns the maximum value in an R83VEC.
• R83VEC_MIN returns the minimum value in an R83VEC.
• S_LEN_TRIM returns the length of a string to the last nonblank.
• S_TO_R8 reads an R8 from a string.
• S_TO_R8VEC reads an R8VEC from a string.
• SPIN_IMAGE adjusts the angle of rotation and redisplays the picture.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• XYZ_DATA_PRINT prints the data for an XYZ file.
• XYZ_DATA_READ reads the data in an XYZ file.
• XYZ_HEADER_PRINT prints the header of an XYZ file.
• XYZ_HEADER_READ reads the header of an XYZ file.

You can go up one level to the C++ source codes.