convert gl_spheres to use glMultiDrawElements

Author: mohawk2

lib/PDL/Graphics/OpenGLQ.pd

@@ -55,7 +55,20 @@ pp_addhdr('
     int i; \
     for (i = 0; i < 3; i++) v[i] *= fac; \
   }
-#define BUFFER_OFFSET(i) ((char *)NULL + (i))
+#define BUFFER_OFFSET(i) ((void *)((char *)NULL + (i)))
+#if defined(_WIN32) || (defined(__CYGWIN__) && defined(HAVE_W32API))
+#define loadProc(proc) \
+{ \
+  if (!proc) \
+  { \
+    proc = (void *)wglGetProcAddress(#proc); \
+    if (!proc) croak(#proc " is not supported by this renderer"); \
+  } \
+}
+PFNGLMULTIDRAWELEMENTSPROC glMultiDrawElements;
+#else /* not using WGL */
+#define loadProc(proc)
+#endif /* not defined _WIN32, __CYGWIN__, and HAVE_W32API */
 ');
 
 my @internal = (Doc => 'internal', NoPthread => 1);
@@ -92,6 +105,15 @@ pp_def(
   Pars => 'coords(tri=3,n);',
   OtherPars => 'int dim0; int dim1 => nstacks;',
   Code => <<'EOF',
+loadProc(glMultiDrawElements)
+PDL_Long *counts = malloc(sizeof(PDL_Long*) * $SIZE(nstacks));
+PDL_ULong **indexptrs = malloc(sizeof(PDL_ULong*) * $SIZE(nstacks));
+if (!indexptrs) $CROAK("malloc failed");
+loop(nstacks) %{
+  counts[nstacks] = $COMP(dim0);
+  indexptrs[nstacks] = BUFFER_OFFSET(nstacks * $COMP(dim0) * sizeof(PDL_ULong));
+%}
+broadcastloop %{
 float oldcoord0 = 0.0, oldcoord1 = 0.0, oldcoord2 = 0.0;
 glPushMatrix();
 loop(n) %{
@@ -100,12 +122,11 @@ loop(n) %{
     $coords(tri=>1) - oldcoord1,
     $coords(tri=>2) - oldcoord2
   );
-  loop (nstacks) %{
-    glDrawElements(GL_TRIANGLE_STRIP, $COMP(dim0), GL_UNSIGNED_INT, BUFFER_OFFSET(nstacks * $COMP(dim0) * sizeof(PDL_ULong)));
-  %}
+  glMultiDrawElements(GL_TRIANGLE_STRIP, counts, GL_UNSIGNED_INT, (const GLvoid *const *)indexptrs, $SIZE(nstacks));
   oldcoord0 = $coords(tri=>0), oldcoord1 = $coords(tri=>1), oldcoord2 = $coords(tri=>2);
 %}
 glPopMatrix();
+%}
 EOF
   @internal
 );