Feat(Tests): Add test to reproduce inconsistent morph targets and move into SharpGLTF.ThirdParty.Tests

tests/SharpGLTF.ThirdParty.Tests/InconsistentMorphTargets.cs

@@ -0,0 +1,102 @@
+using NUnit.Framework;
+using System.Numerics;
+
+using SharpGLTF.Geometry;
+using SharpGLTF.Geometry.VertexTypes;
+using SharpGLTF.Scenes;
+using SharpGLTF.Schema2;
+using SharpGLTF.Materials;
+
+namespace SharpGLTF.ThirdParty
+{
+    [TestFixture]
+    public class BugRepro_InconsistentMorphTargets
+    {
+        [Test(Description = "check if all primitives has the same number of morph target.")]
+        public void BuildMesh_WithPartiallyAppliedMorphTargets_AllPrimitivesShouldHaveSameTargetCount()
+        {
+            // use_temp_fix decide whether fix the problem with a trick.
+            bool use_temp_fix = false;
+            var meshBuilder = new MeshBuilder<VertexPosition>("mesh with partial morph targets");
+
+
+            // here we will construct 3 primitive and 2 morph targets.
+            // And the first morph target only involve p_0 and p_1
+            // The 2nd morph target only involve p_1 and p_2
+
+            var material1 = new MaterialBuilder("material1");
+            var material2 = new MaterialBuilder("material2");
+            var material3 = new MaterialBuilder("material3");
+
+            var prim0 = meshBuilder.UsePrimitive(material1);
+            prim0.AddTriangle(
+                new VertexPosition(-1, 0, 0),
+                new VertexPosition(-2, 0, 0),
+                new VertexPosition(-1, 1, 0)
+            ); 
+
+            var prim1 = meshBuilder.UsePrimitive(material2);
+            prim1.AddTriangle(
+                new VertexPosition(0, 0, 0),
+                new VertexPosition(1, 0, 0),
+                new VertexPosition(0, 1, 0)
+            ); 
+
+            var prim2 = meshBuilder.UsePrimitive(material3);
+            prim2.AddTriangle(
+                new VertexPosition(2, 0, 0),
+                new VertexPosition(3, 0, 0),
+                new VertexPosition(2, 1, 0)
+            ); 
+
+            var morphTarget0 = meshBuilder.UseMorphTarget(0);
+            var morphTarget1 = meshBuilder.UseMorphTarget(1);
+
+            morphTarget0.SetVertexDelta(new VertexPosition(-1, 0, 0), new VertexGeometryDelta(new Vector3(0.1f, 0.1f, 0), Vector3.Zero, Vector3.Zero)); 
+            morphTarget0.SetVertexDelta(new VertexPosition(0, 0, 0), new VertexGeometryDelta(new Vector3(0.1f, 0.1f, 0), Vector3.Zero, Vector3.Zero));   
+
+            morphTarget1.SetVertexDelta(new VertexPosition(1, 0, 0), new VertexGeometryDelta(new Vector3(-0.1f, 0.2f, 0), Vector3.Zero, Vector3.Zero)); 
+            morphTarget1.SetVertexDelta(new VertexPosition(3, 0, 0), new VertexGeometryDelta(new Vector3(-0.1f, 0.2f, 0), Vector3.Zero, Vector3.Zero));
+
+            // use_temp_fix decide whether fix the error with a trick
+            if(use_temp_fix)
+            {
+                var morphTarget2 = meshBuilder.UseMorphTarget(2);
+                foreach (var primitive in meshBuilder.Primitives)
+                {
+                    var index = primitive.Vertices[0];
+                    morphTarget2.SetVertexDelta(primitive.Vertices[0].Position, new VertexGeometryDelta(Vector3.Zero, Vector3.Zero, Vector3.Zero));
+                }
+            }
+            
+            var sceneBuilder = new SceneBuilder();
+            sceneBuilder.AddRigidMesh(meshBuilder, Matrix4x4.Identity);
+            var model = sceneBuilder.ToGltf2();
+
+            // save the output glb for test
+            if (use_temp_fix)
+            {
+                model.SaveGLB("../../../../Assets/InconsistentMorphTargets_trick_fixed.glb");
+            }
+            else
+            {
+                model.SaveGLB("../../../../Assets/InconsistentMorphTargets_unfixed.glb");
+            }
+
+            Assert.That(model.LogicalMeshes.Count, Is.EqualTo(1), "The model should have only one mesh");
+            var logicalMesh = model.LogicalMeshes[0];
+
+            Assert.That(logicalMesh.Primitives.Count, Is.EqualTo(3), "The mesh should have three primitives.");
+
+            var prim0_test = logicalMesh.Primitives[0];
+            var prim1_test = logicalMesh.Primitives[1];
+            var prim2_test = logicalMesh.Primitives[2];
+
+            int expectedTargetCount = prim0_test.MorphTargetsCount;
+
+            // check if the number of morph targets of primitives are equal.
+            Assert.That(prim1_test.MorphTargetsCount, Is.EqualTo(expectedTargetCount), "The number of morph targets of the second primitive is not equal to the first one.");
+            Assert.That(prim2_test.MorphTargetsCount, Is.EqualTo(expectedTargetCount), "The number of morph targets of the third primitive is not equal to the first one.");
+        }
+    }
+}