Re: Drawing curved lines in VRML

Timothy F. Rohaly ([email protected])
Mon, 29 May 1995 12:32:59 -0400

On May 24, 10:20, James Waldrop wrote:
> Subject:
>
> Here's a simple question for the 3D / Open Inventor experts out there.
>
> I need to draw a curved line in VRML. I'm drawing this line on the fly,
> with a program (cgi-bin for vrml), and I don't know how to do it. :(
>
> So, let's say that I had a simple curve of the form:
>
> for (y=-10; y <= 10; y++) { x = z = pow(2, y); }
>
> This gets me a set of points.
>
> How do I draw them? I have some clues, but would appreciate real VRML.
>
> Thanks!
>
> James
>-- End of excerpt from James Waldrop

Here is an example program with output:
--------------------------------------------------------------------------------

#include <stdio.h>
#include <math.h>

/*
* Program to generate a VRML file for a line given by
* a functional form. In this case x = z = 2**y.
*
*/
main()
{
int y;
float x,z;

printf("#VRML V1.0 ascii\n\n");
printf("Separator {\n");
printf(" Coordinate3 {\n");
printf(" point [\n");

/* Insert your favorite function here */
for (y = -10; y <= 10; y++) {
x = z = pow(2, y);
printf(" %f %f %f,\n", x, (float) y, z);
}

printf(" ]\n");
printf(" }\n");
printf(" IndexedLineSet {\n");
printf(" coordIndex [\n ");
for (y = 0; y < 21; y++) { /* This also depends on your function */
printf("%d, ",y);
}
printf("-1,\n");
printf(" ]\n");
printf(" }\n");
printf("}\n");

return 0;
}

Output:
--------------------------------------------------------------------------------

#VRML V1.0 ascii

Separator {
Coordinate3 {
point [
0.000977 -10.000000 0.000977,
0.001953 -9.000000 0.001953,
0.003906 -8.000000 0.003906,
0.007812 -7.000000 0.007812,
0.015625 -6.000000 0.015625,
0.031250 -5.000000 0.031250,
0.062500 -4.000000 0.062500,
0.125000 -3.000000 0.125000,
0.250000 -2.000000 0.250000,
0.500000 -1.000000 0.500000,
1.000000 0.000000 1.000000,
2.000000 1.000000 2.000000,
4.000000 2.000000 4.000000,
8.000000 3.000000 8.000000,
16.000000 4.000000 16.000000,
32.000000 5.000000 32.000000,
64.000000 6.000000 64.000000,
128.000000 7.000000 128.000000,
256.000000 8.000000 256.000000,
512.000000 9.000000 512.000000,
1024.000000 10.000000 1024.000000,
]
}
IndexedLineSet {
coordIndex [
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19
, 20, -1,
]
}
}