X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=hacks%2Fglx%2Fmolecule.c;h=cb2932eb7168c232dec3fe8cc102371f3c069191;hb=8eb2873d7054e705c4e83f22d18c40946a9e2529;hp=954b98101dc03014adca815b485e016d06499597;hpb=585e1a6717d1dd9b90fbb53acaaae82106354d33;p=xscreensaver

diff --git a/hacks/glx/molecule.c b/hacks/glx/molecule.c
index 954b9810..cb2932eb 100644
--- a/hacks/glx/molecule.c
+++ b/hacks/glx/molecule.c
@@ -22,6 +22,49 @@
      - I'm not sure the text labels are being done in the best way;
        they are sometimes, but not always, occluded by spheres that
        pass in front of them. 
+
+   GENERAL OPENGL NAIVETY:
+
+       I don't understand the *right* way to place text in front of the
+       atoms.  What I'm doing now is close, but has glitches.  I think I
+       understand glPolygonOffset(), but I think it doesn't help me.
+
+       Here's how I'd phrase the problem I'm trying to solve:
+
+       - I have a bunch of spherical objects of various sizes
+       - I want a piece of text in the scene, between each object
+         and the observer
+       - the position of this text should be apparently tangential 
+         to the surface of the sphere, so that:
+         - it is never inside the sphere;
+         - but can be occluded by other objects in the scene.
+
+       So I was trying to use glPolygonOffset() to say "pretend all
+       polygons are N units deeper than they actually are" where N was
+       somewhere around the maximal radius of the objects.  Which wasn't a
+       perfect solution, but was close.  But it turns out that can't work,
+       because the second arg to glPolygonOffset() is multiplied by some
+       minimal depth quantum which is not revealed, so I can't pass it an
+       offset in scene units -- only in multiples of the quantum.  So I
+       don't know how many quanta in radius my spheres are.
+
+       I think I need to position and render the text with glRasterPos3f()
+       so that the text is influenced by the depth buffer.  If I used 2f,
+       or an explicit constant Z value, then the text would always be in
+       front of each sphere, and text would be visible for spheres that
+       were fully occluded, which isn't what I want.
+
+       So my only guess at this point is that I need to position the text
+       exactly where I want it, tangential to the spheres -- but that
+       means I need to be able to compute that XYZ position, which is
+       dependent on the position of the observer!  Which means two things:
+       first, while generating my scene, I need to take into account the
+       position of the observer, and I don't have a clue how to do that;
+       and second, it means I can't put my whole molecule in a display
+       list, because the XYZ position of the text in the scene changes at
+       every frame, as the molecule rotates.
+
+       This just *can't* be as hard as it seems!
  */
 
 #include <X11/Intrinsic.h>
@@ -186,7 +229,7 @@ static XrmOptionDescRec opts[] = {
   { "-molecule", ".molecule", XrmoptionSepArg, 0 },
   { "-timeout",".timeout",XrmoptionSepArg, 0 },
   { "-spin",   ".spin",   XrmoptionSepArg, 0 },
-  { "+spin",   ".spin",   XrmoptionNoArg, "" },
+  { "+spin",   ".spin",   XrmoptionNoArg, "False" },
   { "-wander", ".wander", XrmoptionNoArg, "True" },
   { "+wander", ".wander", XrmoptionNoArg, "False" },
   { "-labels", ".labels", XrmoptionNoArg, "True" },
@@ -552,7 +595,8 @@ print_title_string (ModeInfo *mi, const char *string,
   
   y -= line_height;
 
-  glPushAttrib (GL_LIGHTING | GL_DEPTH_TEST);
+  glPushAttrib (GL_TRANSFORM_BIT |  /* for matrix contents */
+                GL_ENABLE_BIT);     /* for various glDisable calls */
   glDisable (GL_LIGHTING);
   glDisable (GL_DEPTH_TEST);
   {
@@ -622,6 +666,7 @@ build_molecule (ModeInfo *mi)
       glEnable(GL_CULL_FACE);
     }
 
+#if 0
   if (do_labels && !wire)
     {
       /* This is so all polygons are drawn slightly farther back in the depth
@@ -634,6 +679,7 @@ build_molecule (ModeInfo *mi)
     {
       glDisable (GL_POLYGON_OFFSET_FILL);
     }
+#endif
 
   if (!wire)
     set_atom_color (mi, 0, False);
@@ -689,16 +735,20 @@ build_molecule (ModeInfo *mi)
         molecule_atom *a = &m->atoms[i];
         int j;
 
-        glPushAttrib (GL_LIGHTING | GL_DEPTH_TEST);
-        glDisable (GL_LIGHTING);
-/*        glDisable (GL_DEPTH_TEST);*/
+        if (!wire)
+          {
+            glDisable (GL_LIGHTING);
+#if 1
+            glDisable (GL_DEPTH_TEST);
+#endif
+          }
 
         if (!wire)
           set_atom_color (mi, a, True);
 
         glRasterPos3f (a->x, a->y, a->z);
 
-        /* Before drawing the string, shift the origin  to center
+        /* Before drawing the string, shift the origin to center
            the text over the origin of the sphere. */
         glBitmap (0, 0, 0, 0,
                   -string_width (mc->xfont1, a->label) / 2,
@@ -708,7 +758,17 @@ build_molecule (ModeInfo *mi)
         for (j = 0; j < strlen(a->label); j++)
           glCallList (mc->font1_dlist + (int)(a->label[j]));
 
-        glPopAttrib();
+        /* More efficient to always call glEnable() with correct values
+           than to call glPushAttrib()/glPopAttrib(), since reading
+           attributes from GL does a round-trip and  stalls the pipeline.
+         */
+        if (!wire)
+          {
+            glEnable(GL_LIGHTING);
+#if 1
+            glEnable(GL_DEPTH_TEST);
+#endif
+          }
       }
 
   if (do_bbox)
@@ -1098,7 +1158,7 @@ reshape_molecule (ModeInfo *mi, int width, int height)
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
 
-  gluPerspective( 30.0, 1/h, 1.0, 100.0 );
+  gluPerspective( 30.0, 1/h, 20.0, 40.0 );
   gluLookAt( 0.0, 0.0, 15.0,
              0.0, 0.0, 0.0,
              0.0, 1.0, 0.0);