Merge pull request #5 from kruland2607/bugfixes-1

Bugfixes 1

core/src/net/sf/openrocket/file/openrocket/importt/OpenRocketLoader.java

@@ -1494,7 +1494,7 @@ class SimulationConditionsHandler extends AbstractElementHandler {
 		} else if (element.equals("atmosphere")) {
 			atmosphereHandler.storeSettings(conditions, warnings);
 		} else if (element.equals("timestep")) {
-			if (Double.isNaN(d)) {
+			if (Double.isNaN(d) || d <= 0 ) {
 				warnings.add("Illegal time step defined, ignoring.");
 			} else {
 				conditions.setTimeStep(d);

core/src/net/sf/openrocket/rocketcomponent/FinSet.java

@@ -440,7 +440,7 @@ public abstract class FinSet extends ExternalComponent {
 			
 			double da = (y0 + y1) * (x1 - x0) / 2;
 			finArea += da;
-			if (Math.abs(y0 - y1) < 0.00001) {
+			if (Math.abs(y0 + y1) < 0.00001) {
 				finCGx += (x0 + x1) / 2 * da;
 				finCGy += y0 / 2 * da;
 			} else {

core/src/net/sf/openrocket/simulation/RK4SimulationStepper.java

@@ -139,7 +139,8 @@ public class RK4SimulationStepper extends AbstractSimulationStepper {
 		double[] dt = new double[8];
 		Arrays.fill(dt, Double.MAX_VALUE);
 
-		dt[0] = status.getSimulationConditions().getTimeStep();
+		// If the user selected a really small timestep, use MIN_TIME_STEP instead.
+		dt[0] = MathUtil.max(status.getSimulationConditions().getTimeStep(),MIN_TIME_STEP);
 		dt[1] = maxTimeStep;
 		dt[2] = status.getSimulationConditions().getMaximumAngleStep() / store.lateralPitchRate;
 		dt[3] = Math.abs(MAX_ROLL_STEP_ANGLE / store.flightConditions.getRollRate());

core/test/net/sf/openrocket/rocketcomponent/FinSetTest.java

@@ -1,6 +1,8 @@
 package net.sf.openrocket.rocketcomponent;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import java.awt.Color;
 
@@ -11,6 +13,7 @@ import net.sf.openrocket.rocketcomponent.ExternalComponent.Finish;
 import net.sf.openrocket.rocketcomponent.FinSet.CrossSection;
 import net.sf.openrocket.rocketcomponent.FinSet.TabRelativePosition;
 import net.sf.openrocket.rocketcomponent.RocketComponent.Position;
+import net.sf.openrocket.util.Coordinate;
 import net.sf.openrocket.util.LineStyle;
 import net.sf.openrocket.util.BaseTestCase.BaseTestCase;
 
@@ -18,6 +21,151 @@ import org.junit.Test;
 
 public class FinSetTest extends BaseTestCase {
 
+	@Test
+	public void testTrapezoidCGComputation() {
+
+		{
+			// This is a simple square fin with sides of 1.0.
+			TrapezoidFinSet fins = new TrapezoidFinSet();
+			fins.setFinCount(1);
+			fins.setFinShape(1.0, 1.0, 0.0, 1.0, .005);
+
+			Coordinate coords = fins.getCG();
+			assertEquals(1.0, fins.getFinArea(), 0.001);
+			assertEquals(0.5, coords.x, 0.001);
+			assertEquals(0.5, coords.y, 0.001);
+		}
+
+		{
+			// This is a trapezoid.  Height 1, root 1, tip 1/2 no sweep.
+			// It can be decomposed into a rectangle followed by a triangle
+			//  +---+
+			//  |    \
+			//  |     \
+			//  +------+
+			TrapezoidFinSet fins = new TrapezoidFinSet();
+			fins.setFinCount(1);
+			fins.setFinShape(1.0, 0.5, 0.0, 1.0, .005);
+
+			Coordinate coords = fins.getCG();
+			assertEquals(0.75, fins.getFinArea(), 0.001);
+			assertEquals(0.3889, coords.x, 0.001);
+			assertEquals(0.4444, coords.y, 0.001);
+		}
+
+	}
+
+	@Test
+	public void testFreeformCGComputation() throws Exception {
+
+		{
+			// This is a trapezoid.  Height 1, root 1, tip 1/2 no sweep.
+			// It can be decomposed into a rectangle followed by a triangle
+			//  +---+
+			//  |    \
+			//  |     \
+			//  +------+
+			FreeformFinSet fins = new FreeformFinSet();
+			fins.setFinCount(1);
+			Coordinate[] points = new Coordinate[] {
+					new Coordinate(0,0),
+					new Coordinate(0,1),
+					new Coordinate(.5,1),
+					new Coordinate(1,0)
+			};
+			fins.setPoints(points);
+			Coordinate coords = fins.getCG();
+			assertEquals(0.75, fins.getFinArea(), 0.001);
+			assertEquals(0.3889, coords.x, 0.001);
+			assertEquals(0.4444, coords.y, 0.001);
+		}
+
+		{
+			// This is the same trapezoid as previous free form, but it has
+			// some extra points along the lines.
+			FreeformFinSet fins = new FreeformFinSet();
+			fins.setFinCount(1);
+			Coordinate[] points = new Coordinate[] {
+					new Coordinate(0,0),
+					new Coordinate(0,.5),
+					new Coordinate(0,1),
+					new Coordinate(.25,1),
+					new Coordinate(.5,1),
+					new Coordinate(.75,.5),
+					new Coordinate(1,0)
+			};
+			fins.setPoints(points);
+			Coordinate coords = fins.getCG();
+			assertEquals(0.75, fins.getFinArea(), 0.001);
+			assertEquals(0.3889, coords.x, 0.001);
+			assertEquals(0.4444, coords.y, 0.001);
+		}
+
+		{
+			// This is the same trapezoid as previous free form, but it has
+			// some extra points which are very close to previous points.
+			// in particular for points 0 & 1,
+			// y0 + y1 is very small.
+			FreeformFinSet fins = new FreeformFinSet();
+			fins.setFinCount(1);
+			Coordinate[] points = new Coordinate[] {
+					new Coordinate(0,0),
+					new Coordinate(0,1E-15),
+					new Coordinate(0,1),
+					new Coordinate(1E-15,1),
+					new Coordinate(.5,1),
+					new Coordinate(.5,1-1E-15),
+					new Coordinate(1,1E-15),
+					new Coordinate(1,0)
+			};
+			fins.setPoints(points);
+			Coordinate coords = fins.getCG();
+			assertEquals(0.75, fins.getFinArea(), 0.001);
+			assertEquals(0.3889, coords.x, 0.001);
+			assertEquals(0.4444, coords.y, 0.001);
+		}
+
+	}
+
+	@Test
+	public void testFreeFormCGWithNegativeY() throws Exception {
+		// This particular fin shape is currently not allowed in OR since the y values are negative
+		// however, it is possible to convert RockSim files and end up with fins which
+		// have negative y values.
+		
+		// A user submitted an ork file which could not be simulated because the fin
+		// was constructed on a tail cone.  It so happened that for one pair of points
+		// y_n = - y_(n+1) which caused a divide by zero and resulted in CGx = NaN.
+		
+		// This Fin set is constructed to have the same problem.  It is a square and rectagle
+		// where the two trailing edge corners of the rectangle satisfy y_0 = -y_1
+		//
+		// +---------+
+		// |         |
+		// |         |
+		// +----+    |
+		//      |    |
+		//      |    |
+		//      +----+
+		
+		FreeformFinSet fins = new FreeformFinSet();
+		fins.setFinCount(1);
+		Coordinate[] points = new Coordinate[] {
+				new Coordinate(0,0),
+				new Coordinate(0,1),
+				new Coordinate(2,1),
+				new Coordinate(2,-1),
+				new Coordinate(1,-1),
+				new Coordinate(1,0)
+		};
+		fins.setPoints(points);
+		Coordinate coords = fins.getCG();
+		assertEquals(3.0, fins.getFinArea(), 0.001);
+		assertEquals(3.5/3.0, coords.x, 0.001);
+		assertEquals(0.5/3.0, coords.y, 0.001);
+
+	}
+
 
 	@Test
 	public void testFreeformConvert() {