diff --git a/demo/extractmesh.c b/demo/extractmesh.c
index 299ddeb..d34a8a6 100644
--- a/demo/extractmesh.c
+++ b/demo/extractmesh.c
@@ -18,24 +18,39 @@ void writemesh(const struct MeshHeader *mh,
     // mesh header offset batches need to be changed for compability with parsing.
     struct MeshHeader newmh = *(mh);
     newmh.offsetBatches = sizeof(struct Header) + sizeof(struct MeshHeader);
-    // batch data the same treatment.
-    struct BatchData newbatch = *(m -> b) -> bd;
-    unsigned int vertices = m -> b -> bd -> numVertex;
-    newbatch.offsetPositions   = sizeof(struct MeshHeader)  + sizeof(struct BatchData);
-    newbatch.offsetNormals     = newbatch.offsetPositions   + (sizeof(struct Coordinate)  * vertices);
-    newbatch.offsetUVs         = newbatch.offsetNormals     + (sizeof(struct Coordinate)  * vertices);
-    newbatch.offsetBoneIndexes = newbatch.offsetUVs         + (sizeof(struct UVs)         * vertices);
-    newbatch.offsetBoneWeights = newbatch.offsetBoneIndexes + (sizeof(struct BoneIndexes) * vertices);
-    // write to file.
     write(fn, (char*)(&h),         sizeof(struct Header));
     append(fn, (char*)(&newmh),    sizeof(struct MeshHeader));
-    append(fn, (char*)(&newbatch), sizeof(struct BatchData));
-    append(fn, (char*)(m -> b -> vd.positions), sizeof(struct Coordinate)  * vertices);
-    DEVIL1GEO.printcoordinate(m -> b -> vd.positions, 3);
-    append(fn, (char*)(m -> b -> vd.normals),   sizeof(struct Coordinate)  * vertices);
-    append(fn, (char*)(m -> b -> vd.u),         sizeof(struct UVs)         * vertices);
-    append(fn, (char*)(m -> b -> vd.bi),        sizeof(struct BoneIndexes) * vertices);
-    append(fn, (char*)(m -> b -> vd.bw),        sizeof(struct BoneWeights) * vertices);
+
+    struct BatchData * newBatches = malloc(newmh.numBatch * sizeof(struct BatchData));
+    // batch data the same treatment.
+    uint64_t previousBatch = 0;
+    for (int i = 0; i < newmh.numBatch; i++) {
+      newBatches[i] = (m -> b) -> bd[i];
+      unsigned int nVertices = m -> b -> bd[i].numVertex;
+      if (previousBatch == 0) {
+        newBatches[i].offsetPositions = newmh.offsetBatches + ( newmh.numBatch * sizeof(struct BatchData));
+      }
+      else {
+        newBatches[i].offsetPositions = previousBatch;
+      }
+      newBatches[i].offsetNormals     = newBatches[i].offsetPositions   + (sizeof(struct Coordinate)  * nVertices);
+      newBatches[i].offsetUVs         = newBatches[i].offsetNormals     + (sizeof(struct Coordinate)  * nVertices);
+      newBatches[i].offsetBoneIndexes = newBatches[i].offsetUVs         + (sizeof(struct UVs)         * nVertices);
+      newBatches[i].offsetBoneWeights = newBatches[i].offsetBoneIndexes + (sizeof(struct BoneIndexes) * nVertices);
+      append(fn, (char*)(&newBatches[i]), sizeof(struct BatchData));
+      previousBatch                   = newBatches[i].offsetBoneWeights + (sizeof(struct BoneWeights) * nVertices);;
+    }
+
+    for (int i = 0; i < newmh.numBatch; i++) {
+      unsigned int nVertices = m -> b -> bd[i].numVertex;
+      append(fn, (char*)(m -> b[i].vd.positions), sizeof(struct Coordinate)  * nVertices);
+      DEVIL1GEO.printcoordinate(m -> b -> vd.positions, 3);
+      append(fn, (char*)(m -> b[i].vd.normals),   sizeof(struct Coordinate)  * nVertices);
+      append(fn, (char*)(m -> b[i].vd.u),         sizeof(struct UVs)         * nVertices);
+      append(fn, (char*)(m -> b[i].vd.bi),        sizeof(struct BoneIndexes) * nVertices);
+      append(fn, (char*)(m -> b[i].vd.bw),        sizeof(struct BoneWeights) * nVertices);
+    }
+
     free(fn);
 }