Function:ds2tb

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ds2tb

Draw text that always faces the camera

Prototype

void ds2tb(float x, float y, float z, float x_off, float y_off, char *text, int scaletext);

Description

Draw text at position (x,y,z) that always faces the camera. Use this function only from within a dynamic callback. offset is in character units along Right and Up vectors - use this to displace labels in screen coordinates. If scaletext is true (non-zero), then text further from the camera will be made larger so that labels are equally legible for all distances.

NOTE: this function uses the S2PLOT attributes for character height (size) and colour.

See Also

ds2bb Draw a (dynamic) billboard: a textured facet that always faces the camera
ds2vbb Draw a (dynamic) billboard: a textured facet that always faces the camera - vector input
ds2vtb Draw text that always faces the camera - vector input
s2sci Set the pen colour by index.
s2sch Set the character height in "arbitrary" units.


Code Example

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include "s2plot.h"

float *x, *y, *z;			/* Global arrays - text positions */
int N;					/* Number of text labels */

void cb(double *t, int *kc)
/* A dynamic callback */
{
   int i;				/* Loop variable */
   float xoff = 0.01;			/* Small offsets - must be non-zero */
   float yoff = 0.01;			/*  for text to appear */
   
   s2sch(0.2);				/* Set the text height */
   for (i=0;i<N;i++) {			/* Draw the billboard labels */
      ds2tb(x[i], y[i], z[i], xoff, yoff, "S2PLOT", 1);
   }
}


int main(int argc, char *argv[])
{
   int i;					/* Loop variable */
   srand48((long)time(NULL));			/* Seed random numbers */

   s2opend("/S2MONO",argc,argv);		/* Open the display */
   s2swin(-1.5,1.5, -1.5,1.5, -1.5,1.5);
   s2box("BCDE",0,0,"BCDE",0,0,"BCDE",0,0);	/* Draw coord box */

   N = 20;					/* Number of labels to draw */
   x = (float *)calloc(N, sizeof(float));
   y = (float *)calloc(N, sizeof(float));
   z = (float *)calloc(N, sizeof(float));

   for (i=0;i<N;i++) {			/* Create N random (x,y,z) values */
      x[i] = drand48()*2.0 - 1.0;
      y[i] = drand48()*2.0 - 1.0;
      z[i] = drand48()*2.0 - 1.0;
   }
 
   cs2scb(cb);				/* Install a dynamic callback */

   s2show(1);				/* Open the s2plot window */

   return 1;
}

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