Add a configuration option to hide the back faces; that gets rid of

stray red pixels sometimes, if the mesh is leaky or the graphics
card isn't perfect.

[git-p4: depot-paths = "//depot/solvespace/": change = 1864]

draw.cpp

@@ -960,9 +960,14 @@ void GraphicsWindow::Paint(int w, int h) {
     GLfloat ld1[4] = { (GLfloat)ld.x, (GLfloat)ld.y, (GLfloat)ld.z, 0 };
     glLightfv(GL_LIGHT1, GL_POSITION, ld1);
 
-    // For debugging, draw the backs of the triangles in red, so that we
+    if(SS.drawBackFaces) {
-    // notice when a shell is open
+        // For debugging, draw the backs of the triangles in red, so that we
-    glLightModelf(GL_LIGHT_MODEL_TWO_SIDE, 1);
+        // notice when a shell is open
+        glLightModelf(GL_LIGHT_MODEL_TWO_SIDE, 1);
+    } else {
+        glLightModelf(GL_LIGHT_MODEL_TWO_SIDE, 0);
+    }
+
     GLfloat ambient[4] = { 0.4f, 0.4f, 0.4f, 1.0f };
     glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambient);
 

solvespace.cpp

@@ -49,6 +49,8 @@ void SolveSpace::Init(char *cmdLine) {
     edgeColor = CnfThawDWORD(RGB(0, 0, 0), "EdgeColor");
     // Export scale factor
     exportScale = CnfThawFloat(1.0f, "ExportScale");
+    // Draw back faces of triangles (when mesh is leaky/self-intersecting)
+    drawBackFaces = CnfThawDWORD(1, "DrawBackFaces");
     // Recent files menus
     for(i = 0; i < MAX_RECENT; i++) {
         char name[100];
@@ -107,6 +109,8 @@ void SolveSpace::Exit(void) {
     CnfFreezeDWORD(edgeColor, "EdgeColor");
     // Export scale (a float, stored as a DWORD)
     CnfFreezeFloat(exportScale, "ExportScale");
+    // Draw back faces of triangles (when mesh is leaky/self-intersecting)
+    CnfFreezeDWORD(drawBackFaces, "DrawBackFaces");
 
     ExitNow();
 }

solvespace.h

@@ -370,6 +370,7 @@ public:
     double  cameraTangent;
     DWORD   edgeColor;
     float   exportScale;
+    int     drawBackFaces;
 
     int CircleSides(double r);
     typedef enum {

textscreens.cpp

@@ -595,6 +595,10 @@ void TextWindow::ScreenChangeExportScale(int link, DWORD v) {
     ShowTextEditControl(59, 3, str);
     SS.TW.edit.meaning = EDIT_EXPORT_SCALE;
 }
+void TextWindow::ScreenChangeBackFaces(int link, DWORD v) {
+    SS.drawBackFaces = !SS.drawBackFaces;
+    InvalidateGraphics();
+}
 void TextWindow::ShowConfiguration(void) {
     int i;
     Printf(true, "%Ft material   color-(r, g, b)");
@@ -648,6 +652,14 @@ void TextWindow::ShowConfiguration(void) {
     Printf(false, "%Ba   %3 %Fl%Ll%f%D[change]%E",
         (double)SS.exportScale,
         &ScreenChangeExportScale, 0);
+
+    Printf(false, "");
+    Printf(false, "%Ft draw back faces: "
+                  "%Fh%f%Ll%s%E%Fs%s%E / %Fh%f%Ll%s%E%Fs%s%E",
+        &ScreenChangeBackFaces,
+        (SS.drawBackFaces ? "" : "yes"), (SS.drawBackFaces ? "yes" : ""),
+        &ScreenChangeBackFaces,
+        (!SS.drawBackFaces ? "" : "no"), (!SS.drawBackFaces ? "no" : ""));
 }
 
 //-----------------------------------------------------------------------------

ui.h

@@ -139,6 +139,8 @@ public:
     static void ScreenShowConfiguration(int link, DWORD v);
     static void ScreenGoToWebsite(int link, DWORD v);
 
+    static void ScreenChangeBackFaces(int link, DWORD v);
+
     static void ScreenStepDimSteps(int link, DWORD v);
     static void ScreenStepDimFinish(int link, DWORD v);
     static void ScreenStepDimGo(int link, DWORD v);