feat: expand attribute scheme to allow combining meshdata

engine-tests/src/test/java/org/terasology/engine/rendering/assets/mesh/StandardMeshDataTest.java

@@ -0,0 +1,45 @@
+// Copyright 2021 The Terasology Foundation
+// SPDX-License-Identifier: Apache-2.0
+
+package org.terasology.engine.rendering.assets.mesh;
+
+import org.joml.Matrix4f;
+import org.joml.Vector3f;
+import org.junit.Assert;
+import org.junit.jupiter.api.Test;
+import org.terasology.joml.test.VectorAssert;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class StandardMeshDataTest {
+
+    @Test
+    public void testCombineMeshes() {
+        StandardMeshData m1 = new StandardMeshData();
+        m1.position.put(new Vector3f(10f, 10f, 10f));
+        m1.position.put(new Vector3f(15f, 20f, 10f));
+        m1.position.put(new Vector3f(10f, 30f, 10f));
+
+        StandardMeshData m2 = new StandardMeshData();
+        m2.position.put(new Vector3f(10f, 10f, 10f));
+        m2.position.put(new Vector3f(15f, 20f, 10f));
+        m2.position.put(new Vector3f(10f, 30f, 10f));
+
+        m1.combine(new Matrix4f(), m2);
+
+        assertEquals(m1.position.getPosition(), 6);
+        assertEquals(m1.normal.getPosition(), 0);
+        assertEquals(m1.uv0.getPosition(), 0);
+        assertEquals(m1.uv1.getPosition(), 0);
+        assertEquals(m1.color0.getPosition(), 0);
+
+        VectorAssert.assertEquals(m1.position.get(0, new Vector3f()), new Vector3f(10f, 10f, 10f), .001f);
+        VectorAssert.assertEquals(m1.position.get(1, new Vector3f()), new Vector3f(15f, 20f, 10f), .001f);
+        VectorAssert.assertEquals(m1.position.get(2, new Vector3f()), new Vector3f(10f, 30f, 10f), .001f);
+
+        VectorAssert.assertEquals(m1.position.get(3, new Vector3f()), new Vector3f(10f, 10f, 10f), .001f);
+        VectorAssert.assertEquals(m1.position.get(4, new Vector3f()), new Vector3f(15f, 20f, 10f), .001f);
+        VectorAssert.assertEquals(m1.position.get(5, new Vector3f()), new Vector3f(10f, 30f, 10f), .001f);
+
+    }
+}

engine/src/main/java/org/terasology/engine/rendering/assets/mesh/StandardMeshData.java

@@ -3,6 +3,7 @@
 
 package org.terasology.engine.rendering.assets.mesh;
 
+import org.joml.Matrix4f;
 import org.joml.Vector2f;
 import org.joml.Vector2fc;
 import org.joml.Vector3f;
@@ -123,6 +124,37 @@ public void reallocate(int numVerts, int numIndices) {
         indices.allocateElements(numIndices);
     }
 
+
+    public void combine(Matrix4f transform, StandardMeshData data) {
+        combine(transform, this.position.getPosition(), data);
+    }
+
+    public void combine(Matrix4f transform, int offset, StandardMeshData data) {
+        if (!position.isEmpty() || !data.position.isEmpty()) {
+            position.setPosition(offset);
+            Vector3f temp = new Vector3f();
+            for (int i = 0; i < data.position.elements(); i++) {
+                this.position.put(transform.transformPosition(data.position.get(i, temp)));
+            }
+        }
+        if (!normal.isEmpty() || !data.normal.isEmpty()) {
+            VertexAttributeBinding.copy(data.normal, offset, this.normal, new Vector3f());
+        }
+        if (!uv0.isEmpty() || !data.uv0.isEmpty()) {
+            VertexAttributeBinding.copy(data.uv0, offset, this.uv0, new Vector2f());
+        }
+        if (!uv1.isEmpty() || !data.uv1.isEmpty()) {
+            VertexAttributeBinding.copy(data.uv1, offset, this.uv1, new Vector2f());
+        }
+        if (!color0.isEmpty() || !data.color0.isEmpty()) {
+            VertexAttributeBinding.copy(data.color0, offset, this.color0, new Color());
+        }
+        if (!light0.isEmpty() || !data.light0.isEmpty()) {
+            VertexAttributeBinding.copy(data.light0, offset, this.light0, new Vector3f());
+        }
+    }
+
+
     @Override
     public VertexAttributeBinding<Vector3fc, Vector3f> positions() {
         return position;

engine/src/main/java/org/terasology/engine/rendering/assets/mesh/resource/VertexAttributeBinding.java

@@ -16,11 +16,14 @@ public VertexAttributeBinding(VertexResource resource, int offset, VertexAttribu
         this.attribute = attribute;
     }
 
-
     public int elements() {
         return getResource().elements();
     }
 
+    public boolean isEmpty() {
+        return getResource().isEmpty();
+    }
+
     @Override
     public void reserve(int vertCount) {
         resource.reserveElements(vertCount);
@@ -32,6 +35,22 @@ public void allocate(int elements) {
         resource.mark();
     }
 
+    /**
+     *
+     * @param from data getting copied from
+     * @param position position to start copying to dest
+     * @param dest the destination to fill
+     * @param target a temporary object to transfer data between from and dest
+     * @param <T>
+     * @param <I>
+     */
+    public static <T,I extends T> void copy(VertexAttributeBinding<T, I> from, int position, VertexAttributeBinding<T, I> dest, I target) {
+        dest.setPosition(position);
+        for (int i = 0; i < from.elements(); i++) {
+            dest.put(from.get(i, target));
+        }
+    }
+
     /**
      * write a value by the index.
      *