solve issue #1919 (underflow while generating tangents) (#1920)

* jme-core:  add a test for issue #1919 (underflow generating tangents)

* MikktspaceTangentGenerator: solve #1919 (underflow generating tangents)

jme3-core/src/main/java/com/jme3/util/mikktspace/MikktspaceTangentGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2021 jMonkeyEngine
+ * Copyright (c) 2009-2023 jMonkeyEngine
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -112,13 +112,39 @@ public class MikktspaceTangentGenerator {
             for (Spatial child : n.getChildren()) {
                 generate(child);
             }
-        } else if (s instanceof Geometry){
-            Geometry g = (Geometry)s;
-            MikkTSpaceImpl context = new MikkTSpaceImpl(g.getMesh());
-            if(!genTangSpaceDefault(context)){
-                logger.log(Level.SEVERE, "Failed to generate tangents for geometry {0}", g.getName());
+
+        } else if (s instanceof Geometry) {
+            Geometry g = (Geometry) s;
+            Mesh mesh = g.getMesh();
+
+            Mesh.Mode mode = mesh.getMode();
+            boolean hasTriangles;
+            switch (mode) {
+                case Points:
+                case Lines:
+                case LineStrip:
+                case LineLoop:
+                    hasTriangles = false; // skip this mesh
+                    break;
+
+                case Triangles:
+                case TriangleFan:
+                case TriangleStrip:
+                    hasTriangles = true;
+                    break;
+
+                default:
+                    String message = "Tangent generation isn't implemented for mode=" + mode;
+                    throw new UnsupportedOperationException(message);
+            }
+
+            if (hasTriangles) {
+                MikkTSpaceImpl context = new MikkTSpaceImpl(mesh);
+                if (!genTangSpaceDefault(context)) {
+                    logger.log(Level.SEVERE, "Failed to generate tangents for geometry {0}", g.getName());
+                }
+                TangentUtils.generateBindPoseTangentsIfNecessary(mesh);
             }
-            TangentUtils.generateBindPoseTangentsIfNecessary(g.getMesh());
         }
     }
     

jme3-core/src/test/java/com/jme3/util/TestIssue1919.java

@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) 2023 jMonkeyEngine
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
+ *   may be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.jme3.util;
+
+import com.jme3.scene.Geometry;
+import com.jme3.scene.Mesh;
+import com.jme3.scene.VertexBuffer;
+import com.jme3.util.mikktspace.MikktspaceTangentGenerator;
+import java.nio.FloatBuffer;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Verifies how MikktspaceTangentGenerator handles various mesh modes. This was
+ * issue #1919 at GitHub.
+ *
+ * @author Stephen Gold
+ */
+public class TestIssue1919 {
+    /**
+     * The number of axes in a vector.
+     */
+    private static final int numAxes = 3;
+
+    /**
+     * Tests a Hybrid-mode mesh.
+     */
+    @Test(expected = UnsupportedOperationException.class)
+    public void testHybrid() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.Hybrid);
+        MikktspaceTangentGenerator.generate(testGeometry);
+    }
+
+    /**
+     * Tests a LineLoop-mode mesh.
+     */
+    @Test
+    public void testLineLoop() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.LineLoop);
+        MikktspaceTangentGenerator.generate(testGeometry);
+
+        Mesh mesh = testGeometry.getMesh();
+        VertexBuffer tangents = mesh.getBuffer(VertexBuffer.Type.Tangent);
+        Assert.assertNull(tangents); /// skipped this mesh
+    }
+
+    /**
+     * Tests a LineStrip-mode mesh.
+     */
+    @Test
+    public void testLineStrip() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.LineStrip);
+        MikktspaceTangentGenerator.generate(testGeometry);
+
+        Mesh mesh = testGeometry.getMesh();
+        VertexBuffer tangents = mesh.getBuffer(VertexBuffer.Type.Tangent);
+        Assert.assertNull(tangents); /// skipped this mesh
+    }
+
+    /**
+     * Tests a Lines-mode mesh.
+     */
+    @Test
+    public void testLines() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.Lines);
+        MikktspaceTangentGenerator.generate(testGeometry);
+
+        Mesh mesh = testGeometry.getMesh();
+        VertexBuffer tangents = mesh.getBuffer(VertexBuffer.Type.Tangent);
+        Assert.assertNull(tangents); // skipped this mesh
+    }
+
+    /**
+     * Tests a Patch-mode mesh.
+     */
+    @Test(expected = UnsupportedOperationException.class)
+    public void testPatch() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.Patch);
+        MikktspaceTangentGenerator.generate(testGeometry);
+    }
+
+    /**
+     * Tests a Points-mode mesh.
+     */
+    @Test
+    public void testPoints() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.Points);
+        MikktspaceTangentGenerator.generate(testGeometry);
+
+        Mesh mesh = testGeometry.getMesh();
+        VertexBuffer tangents = mesh.getBuffer(VertexBuffer.Type.Tangent);
+        Assert.assertNull(tangents); // skipped this mesh
+    }
+
+    /**
+     * Tests a Triangles-mode mesh.
+     */
+    @Test
+    public void testTriangles() {
+        Geometry testGeometry = createGeometry(Mesh.Mode.Triangles);
+        MikktspaceTangentGenerator.generate(testGeometry);
+
+        Mesh mesh = testGeometry.getMesh();
+        VertexBuffer tangents = mesh.getBuffer(VertexBuffer.Type.Tangent);
+        Assert.assertNotNull(tangents); // generated tangents
+    }
+
+    /**
+     * Generates a geometry in the X-Z plane with the specified mesh mode.
+     *
+     * @param mode the desired mode (not null)
+     * @return a new geometry
+     */
+    private Geometry createGeometry(Mesh.Mode mode) {
+        FloatBuffer normals = BufferUtils.createFloatBuffer(
+                0f, 1f, 0f,
+                0f, 1f, 0f,
+                0f, 1f, 0f,
+                0f, 1f, 0f,
+                0f, 1f, 0f,
+                0f, 1f, 0f
+        );
+        float uvDiameter = 5f;
+        FloatBuffer uvs = BufferUtils.createFloatBuffer(
+                uvDiameter, uvDiameter,
+                0f, 0f,
+                uvDiameter, 0f,
+                uvDiameter, uvDiameter,
+                0f, uvDiameter,
+                0f, 0f
+        );
+        float posRadius = 500f;
+        FloatBuffer positions = BufferUtils.createFloatBuffer(
+                +posRadius, 0f, +posRadius,
+                -posRadius, 0f, -posRadius,
+                -posRadius, 0f, +posRadius,
+                +posRadius, 0f, +posRadius,
+                +posRadius, 0f, -posRadius,
+                -posRadius, 0f, -posRadius
+        );
+        Mesh mesh = new Mesh();
+        mesh.setMode(mode);
+        mesh.setBuffer(VertexBuffer.Type.Normal, numAxes, normals);
+        mesh.setBuffer(VertexBuffer.Type.Position, numAxes, positions);
+        mesh.setBuffer(VertexBuffer.Type.TexCoord, 2, uvs);
+        mesh.updateBound();
+
+        Geometry result = new Geometry("testGeometry" + mode, mesh);
+        return result;
+    }
+}