Added short strut mechanism

core/src/main/java/com/vzome/core/render/RenderedManifestation.java

@@ -434,6 +434,8 @@ protected void resetStrutAttributes( Strut strut )
         AlgebraicNumber len = axis .getLength( offset );
 
         Polyhedron prototypeLengthShape = shapes .getStrutShape( orbit, len );
+        if ( prototypeLengthShape == null )
+            return; // This happens for very short struts, when the shape would be inside-out
         this .mShape = prototypeLengthShape;
 
         int orn = axis .getOrientation();

core/src/main/java/com/vzome/core/viewing/ExportedVEFShapes.java

@@ -26,6 +26,7 @@
 import com.vzome.core.math.symmetry.Axis;
 import com.vzome.core.math.symmetry.Direction;
 import com.vzome.core.math.symmetry.Symmetry;
+import com.vzome.core.parts.FastDefaultStrutGeometry;
 import com.vzome.core.parts.StrutGeometry;
 import com.vzome.core.render.Colors;
 import com.vzome.xml.ResourceLoader;
@@ -121,14 +122,26 @@ protected Polyhedron buildConnectorShape(String pkgName) {
     }
 
     @Override
-    protected StrutGeometry createStrutGeometry(Direction dir) {
+    protected StrutGeometry createStrutGeometry(Direction dir)
+    {
         // automatic struts don't use VEF so don't waste time trying
-        if (!dir.isAutomatic()) {
-            String vefData = loadVefData(dir.getName());
+        if ( ! dir.isAutomatic() ) {
+
+            StrutGeometry shortGeometry = new FastDefaultStrutGeometry( dir );
+            String vefData = loadVefData( dir.getName() + "-short" );
+            if (vefData != null) {
+                VefToShape parser = new VefToShape();
+                parser .parseVEF( vefData, mSymmetry.getField() );
+                shortGeometry = parser .getStrutGeometry( dir.getAxis( Symmetry.PLUS, 0 ) .normal());
+            }
+
+            vefData = loadVefData( dir.getName( ));
             if (vefData != null) {
                 VefToShape parser = new VefToShape();
-                parser.parseVEF(vefData, mSymmetry.getField());
-                return parser.getStrutGeometry(dir.getAxis(Symmetry.PLUS, 0).normal());
+                parser .parseVEF( vefData, mSymmetry.getField() );
+                ExportedVEFStrutGeometry geometry = parser .getStrutGeometry( dir.getAxis( Symmetry.PLUS, 0 ) .normal());
+                geometry .setShortGeometry( shortGeometry );
+                return geometry;
             }
             // strut uses finer logging level than connector since strut fallback is more common.
             final Level logLevel = Level.FINER;
@@ -204,7 +217,7 @@ private class VefToShape extends VefParser
 
         private boolean invertSnubBall = false;
 
-        public StrutGeometry getStrutGeometry( AlgebraicVector prototype )
+        public ExportedVEFStrutGeometry getStrutGeometry( AlgebraicVector prototype )
         {
             // next, get the arbitrary axis that the strut model lies along
             Axis tipAxis = mSymmetry .getAxis( tipVertex );

core/src/main/java/com/vzome/core/viewing/ExportedVEFStrutGeometry.java

@@ -30,6 +30,8 @@ public class ExportedVEFStrutGeometry implements StrutGeometry
 
     public final Set<Integer> fullScaleVertices, halfScaleVertices;  // the polyhedron vertices that must adjust for different strut lengths
 
+    private StrutGeometry shortGeometry = null;
+
     public ExportedVEFStrutGeometry( List<AlgebraicVector> vertices, List< List<Integer> > faces, AlgebraicVector prototype, Set<Integer> fullScaleVertices, Set<Integer> halfScaleVertices, AlgebraicField field )
     {
         prototypeVertices = vertices;
@@ -54,6 +56,10 @@ public List<Face.Triangle> getTriangles()
     public Polyhedron getStrutPolyhedron( AlgebraicNumber length )
     {
         AlgebraicVector tipVertex = prototypeVector .scale( length );
+
+        double maxNonTipDistance = 0;
+        double minTipDistance = tipVertex .toRealVector() .length();
+
         AlgebraicVector midpoint = tipVertex .scale( this .field .createRational( 1, 2 ) );
         if ( field .getName() .equals( "snubDodec" ) && LOGGER.isLoggable(Level.FINE) )
         {
@@ -67,16 +73,35 @@ public Polyhedron getStrutPolyhedron( AlgebraicNumber length )
             AlgebraicVector vertex = prototypeVertices .get( i );
             if ( fullScaleVertices .contains(i) ) {
                 vertex = vertex .plus( tipVertex );
-            } else if ( halfScaleVertices != null && halfScaleVertices .contains(i) ) {
-                vertex = vertex .plus( midpoint );
+                minTipDistance = Math.min( minTipDistance, vertex .toRealVector() .length() );
+            } else {
+                if ( halfScaleVertices != null && halfScaleVertices .contains(i) ) {
+                    vertex = vertex .plus( midpoint );
+                }
+                maxNonTipDistance = Math.max( maxNonTipDistance, vertex .toRealVector() .length() );
             }
             result .addVertex( vertex );
         }
+
+        if ( maxNonTipDistance > minTipDistance ) {
+            // The strut shape will be partially inverted, so we don't want to use it.
+            if ( shortGeometry != null ) {
+                return shortGeometry .getStrutPolyhedron( length );
+            }
+            else
+                return null;
+        }
+
         for (List<Integer> prototypeFace : prototypeFaces) {
             Polyhedron.Face face = result .newFace();
             face .addAll( prototypeFace );
             result .addFace( face );
         }
         return result;
     }
+
+    public void setShortGeometry( StrutGeometry shortGeometry )
+    {
+        this.shortGeometry = shortGeometry;        
+    }
 }