Add Wavefront OBJ support, to supplement the existing STL mesh

export. That doesn't seem very useful, but it's only a few dozen
lines of code.

[git-p4: depot-paths = "//depot/solvespace/": change = 2054]

export.cpp

@@ -340,19 +340,6 @@ double VectorFileWriter::MmToPts(double mm) {
     return (mm/25.4)*72;
 }
 
-bool VectorFileWriter::StringEndsIn(char *str, char *ending) {
-    int i, ls = strlen(str), le = strlen(ending);
-
-    if(ls < le) return false;
-        
-    for(i = 0; i < le; i++) {
-        if(tolower(ending[le-i-1]) != tolower(str[ls-i-1])) {
-            return false;
-        }
-    }
-    return true;
-}
-
 VectorFileWriter *VectorFileWriter::ForFile(char *filename) {
     VectorFileWriter *ret;
     if(StringEndsIn(filename, ".dxf")) {
@@ -552,8 +539,7 @@ void VectorFileWriter::BezierAsNonrationalCubic(DWORD rgb, double width,
 }
 
 //-----------------------------------------------------------------------------
-// Export the mesh as an STL file; it should always be vertex-to-vertex and
-// not self-intersecting, so not much to do.
+// Export a triangle mesh, in the requested format.
 //-----------------------------------------------------------------------------
 void SolveSpace::ExportMeshTo(char *filename) {
     SMesh *m = &(SK.GetGroup(SS.GW.activeGroup)->displayMesh);
@@ -567,18 +553,36 @@ void SolveSpace::ExportMeshTo(char *filename) {
         Error("Couldn't write to '%s'", filename);
         return;
     }
+
+    if(StringEndsIn(filename, ".stl")) {
+        ExportMeshAsStlTo(f, m);
+    } else if(StringEndsIn(filename, ".obj")) {
+        ExportMeshAsObjTo(f, m);
+    } else {
+        Error("Can't identify output file type from file extension of "
+              "filename '%s'; try .stl, .obj.", filename);
+    }
+
+    fclose(f);
+}
+
+//-----------------------------------------------------------------------------
+// Export the mesh as an STL file; it should always be vertex-to-vertex and
+// not self-intersecting, so not much to do.
+//-----------------------------------------------------------------------------
+void SolveSpace::ExportMeshAsStlTo(FILE *f, SMesh *sm) {
     char str[80];
     memset(str, 0, sizeof(str));
     strcpy(str, "STL exported mesh");
     fwrite(str, 1, 80, f);
 
-    DWORD n = m->l.n;
+    DWORD n = sm->l.n;
     fwrite(&n, 4, 1, f);
 
     double s = SS.exportScale;
     int i;
-    for(i = 0; i < m->l.n; i++) {
-        STriangle *tr = &(m->l.elem[i]);
+    for(i = 0; i < sm->l.n; i++) {
+        STriangle *tr = &(sm->l.elem[i]);
         Vector n = tr->Normal().WithMagnitude(1);
         float w;
         w = (float)n.x;           fwrite(&w, 4, 1, f);
@@ -596,8 +600,41 @@ void SolveSpace::ExportMeshTo(char *filename) {
         fputc(0, f);
         fputc(0, f);
     }
+}
 
-    fclose(f);
+//-----------------------------------------------------------------------------
+// Export the mesh as Wavefront OBJ format. This requires us to reduce all the
+// identical vertices to the same identifier, so do that first.
+//-----------------------------------------------------------------------------
+void SolveSpace::ExportMeshAsObjTo(FILE *f, SMesh *sm) {
+    SPointList spl;
+    ZERO(&spl);
+    STriangle *tr;
+    for(tr = sm->l.First(); tr; tr = sm->l.NextAfter(tr)) {
+        spl.IncrementTagFor(tr->a);
+        spl.IncrementTagFor(tr->b);
+        spl.IncrementTagFor(tr->c);
+    }
+
+    // Output all the vertices.
+    SPoint *sp;
+    for(sp = spl.l.First(); sp; sp = spl.l.NextAfter(sp)) {
+        fprintf(f, "v %.10f %.10f %.10f\r\n",
+                        sp->p.x / SS.exportScale,
+                        sp->p.y / SS.exportScale,
+                        sp->p.z / SS.exportScale);
+    }
+
+    // And now all the triangular faces, in terms of those vertices. The
+    // file format counts from 1, not 0.
+    for(tr = sm->l.First(); tr; tr = sm->l.NextAfter(tr)) {
+        fprintf(f, "f %d %d %d\r\n",
+                        spl.IndexForPoint(tr->a) + 1,
+                        spl.IndexForPoint(tr->b) + 1,
+                        spl.IndexForPoint(tr->c) + 1);
+    }
+
+    spl.Clear();
 }
 
 //-----------------------------------------------------------------------------

polygon.cpp

@@ -313,13 +313,19 @@ void SPointList::Clear(void) {
 }
 
 bool SPointList::ContainsPoint(Vector pt) {
-    SPoint *p;
-    for(p = l.First(); p; p = l.NextAfter(p)) {
+    return (IndexForPoint(pt) >= 0);
+}
+
+int SPointList::IndexForPoint(Vector pt) {
+    int i;
+    for(i = 0; i < l.n; i++) {
+        SPoint *p = &(l.elem[i]);
         if(pt.Equals(p->p)) {
-            return true;
+            return i;
         }
     }
-    return false;
+    // Not found, so return negative to indicate that.
+    return -1;
 }
 
 void SPointList::IncrementTagFor(Vector pt) {

polygon.h

@@ -53,6 +53,7 @@ public:
 
     void Clear(void);
     bool ContainsPoint(Vector pt);
+    int IndexForPoint(Vector pt);
     void IncrementTagFor(Vector pt);
     void Add(Vector pt);
 };

solvespace.cpp

@@ -435,7 +435,7 @@ void SolveSpace::MenuFile(int id) {
 
         case GraphicsWindow::MNU_EXPORT_MESH: {
             char exportFile[MAX_PATH] = "";
-            if(!GetSaveFile(exportFile, STL_EXT, STL_PATTERN)) break;
+            if(!GetSaveFile(exportFile, MESH_EXT, MESH_PATTERN)) break;
             SS.ExportMeshTo(exportFile); 
             break;
         }

solvespace.h

@@ -82,8 +82,10 @@ int SaveFileYesNoCancel(void);
 #define PNG_PATTERN "PNG (*.png)\0*.png\0All Files (*)\0*\0\0"
 #define PNG_EXT "png"
 // Triangle mesh
-#define STL_PATTERN "STL Mesh (*.stl)\0*.stl\0All Files (*)\0*\0\0"
-#define STL_EXT "stl"
+#define MESH_PATTERN "STL Mesh (*.stl)\0*.stl\0" \
+                     "Wavefront OBJ Mesh (*.obj)\0*.obj\0" \
+                     "All Files (*)\0*\0\0"
+#define MESH_EXT "stl"
 // NURBS surfaces
 #define SRF_PATTERN "STEP File (*.step;*.stp)\0*.step;*.stp\0" \
                     "All Files(*)\0*\0\0"
@@ -228,6 +230,7 @@ void MakeMatrix(double *mat, double a11, double a12, double a13, double a14,
 void MakePathRelative(char *base, char *path);
 void MakePathAbsolute(char *base, char *path);
 bool StringAllPrintable(char *str);
+bool StringEndsIn(char *str, char *ending);
 
 class System {
 public:
@@ -406,7 +409,6 @@ public:
     Vector ptMin, ptMax;
 
     static double MmToPts(double mm);
-    static bool StringEndsIn(char *str, char *ending);
 
     static VectorFileWriter *ForFile(char *file);
 
@@ -629,6 +631,8 @@ public:
     // And the various export options
     void ExportAsPngTo(char *file);
     void ExportMeshTo(char *file);
+    void ExportMeshAsStlTo(FILE *f, SMesh *sm);
+    void ExportMeshAsObjTo(FILE *f, SMesh *sm);
     void ExportViewOrWireframeTo(char *file, bool wireframe);
     void ExportSectionTo(char *file);
     void ExportWireframeCurves(SEdgeList *sel, SBezierList *sbl,

util.cpp

@@ -88,6 +88,20 @@ bool StringAllPrintable(char *str)
     return true;
 }
 
+bool StringEndsIn(char *str, char *ending)
+{
+    int i, ls = strlen(str), le = strlen(ending);
+
+    if(ls < le) return false;
+        
+    for(i = 0; i < le; i++) {
+        if(tolower(ending[le-i-1]) != tolower(str[ls-i-1])) {
+            return false;
+        }
+    }
+    return true;
+}
+
 void MakeMatrix(double *mat, double a11, double a12, double a13, double a14,
                              double a21, double a22, double a23, double a24,
                              double a31, double a32, double a33, double a34,