Changes between Version 26 and Version 27 of tutorial

Timestamp:

Jun 29, 2013, 4:28:38 PM (12 years ago)

Author:

leon

Comment:

Converter source

tutorial

@@ -510 +510 @@
 == Reading Objects ==
 [[Image(motorBike-subset.png,right)]]
-Sometimes we hit limitations of the visualisation tools for the data that we want to visualize. For example [attachment:motorBike.obj] from [http://openfoam.org OpenFOAM] contains object groups that we want to show colored separately and not as whole. Neither [http://wci.llnl.gov/codes/visit/ VisIt] and [http://paraview.org ParaView] can read [http://en.wikipedia.org/wiki/Wavefront_.obj_file Wavefront OBJ] file with group separation. We are forced to convert [attachment:motorBike.obj] into bunch of files and read them one by one.
+Sometimes we hit limitations of the visualisation tools for the data that we want to visualize. For example [attachment:motorBike.obj] from [http://openfoam.org OpenFOAM] contains object groups that we want to show colored separately and not as whole. Neither [http://wci.llnl.gov/codes/visit/ VisIt] and [http://paraview.org ParaView] can read [http://en.wikipedia.org/wiki/Wavefront_.obj_file Wavefront OBJ] file with group separation. We are forced to convert [attachment:motorBike.obj] into bunch of files and read them one by one. The following {{{wavefront.c}}} converts [attachment:motorBike.obj] into 67 files. Try to open them in VisIt and ParaView.
+{{{
+#!c
+#include <stdio.h>
+#include <GL/glew.h>
+#include <GL/glut.h>
+
+#define MaxVertices 400000
+#define MaxFaces    400000 
+#define MaxGroups   100
+
+GLfloat vertex[MaxVertices][3];
+GLuint  face[MaxFaces][3];
+char    group_name[MaxGroups][80];
+int     start_face[MaxGroups];
+
+int vertices = 0;
+int faces    = 0;
+int groups   = 0;
+
+void read_wavefront(const char *filename)
+{
+  char line[80];
+  FILE *f = fopen(filename, "r");
+  while(fgets(line, sizeof(line), f))
+    switch(line[0])
+      {
+      case 'v':
+        sscanf(&line[1],  "%f %f %f", &vertex[vertices][0],
+               &vertex[vertices][1], &vertex[vertices][2]);
+        ++vertices;
+        break;
+      case 'g':
+        sscanf(&line[1], "%s", group_name[groups]);
+        start_face[groups++] = faces;
+        break;
+      case 'f':
+        sscanf(&line[1],  "%d %d %d", &face[faces][0],
+               &face[faces][1], &face[faces][2]);
+        ++faces;
+        break;
+      }
+  fclose(f);
+  start_face[groups] = faces;
+  printf("Read %d vertices and %d faces within %d groups from %s\n",
+         vertices, faces, groups, filename);
+}
+
+void write_wavefront(int group_number)
+{
+  int i = 0; char n[80], *p = group_name[group_number];
+  while (*p != '%' && *p != '\0') n[i++] = *p++; // remove % from name
+  n[i++] = '.'; n[i++] = 'o'; n[i++] = 'b'; n[i++] = 'j'; n[i] = '\0';
+  FILE *f = fopen(n, "w"); fprintf(f, "# Wavefront OBJ file\n");
+  for (i = 0; i < vertices; i++)
+    fprintf(f, "v %g %g %g\n", vertex[i][0], vertex[i][1], vertex[i][2]);
+  fprintf(f, "g %s\n", group_name[group_number]);
+  for (i = start_face[group_number]; i < start_face[group_number+1]; ++i)
+    fprintf(f, "f %d %d %d\n", face[i][0], face[i][1], face[i][2]);
+  fclose(f);
+}
+
+int main(int argc, char **argv)
+{
+  int i;
+  read_wavefront("motorBike.obj");
+  for(i = 0; i < groups; i++) write_wavefront(i);
+  return 0;
+}
+}}}