+
+void fghGenerateTorus(
+ double dInnerRadius, double dOuterRadius, GLint nSides, GLint nRings, /* input */
+ GLfloat **vertices, GLfloat **normals, int* nVert /* output */
+ )
+{
+ GLfloat iradius = (float)dInnerRadius;
+ GLfloat oradius = (float)dOuterRadius;
+ int i, j;
+
+ /* Pre-computed circle */
+ GLfloat *spsi, *cpsi;
+ GLfloat *sphi, *cphi;
+
+ /* number of unique vertices */
+ if (nSides<2 || nRings<2)
+ {
+ /* nothing to generate */
+ *nVert = 0;
+ return;
+ }
+ *nVert = nSides * nRings;
+
+ if ((*nVert) > 65535)
+ fgWarning("fghGenerateTorus: too many slices or stacks requested, indices will wrap");
+
+ /* precompute values on unit circle */
+ fghCircleTable(&spsi,&cpsi, nRings,FALSE);
+ fghCircleTable(&sphi,&cphi,-nSides,FALSE);
+
+ /* Allocate vertex and normal buffers, bail out if memory allocation fails */
+ *vertices = malloc((*nVert)*3*sizeof(GLfloat));
+ *normals = malloc((*nVert)*3*sizeof(GLfloat));
+ if (!(*vertices) || !(*normals))
+ {
+ free(*vertices);
+ free(*normals);
+ fgError("Failed to allocate memory in fghGenerateTorus");
+ }
+
+ for( j=0; j<nRings; j++ )
+ {
+ for( i=0; i<nSides; i++ )
+ {
+ int offset = 3 * ( j * nSides + i ) ;
+
+ (*vertices)[offset ] = cpsi[j] * ( oradius + cphi[i] * iradius ) ;
+ (*vertices)[offset+1] = spsi[j] * ( oradius + cphi[i] * iradius ) ;
+ (*vertices)[offset+2] = sphi[i] * iradius ;
+ (*normals )[offset ] = cpsi[j] * cphi[i] ;
+ (*normals )[offset+1] = spsi[j] * cphi[i] ;
+ (*normals )[offset+2] = sphi[i] ;
+ }
+ }
+
+ /* Release sin and cos tables */
+ free(spsi);
+ free(cpsi);
+ free(sphi);
+ free(cphi);
+}