Вовремя сохранения сцены пропадают в terrainData , текстуры (Unity)

У меня метод который добавляет эти текстуры выглядит так :

static public void DrawPoint (Vector2 v2, Terrain t, int textnum, float Rotation, float Brushsize, float alpha, string brushnames) {
    if (brushnames != null) {
        Debug.Log ("PosX " + v2.x + "PosY " + v2.y);
        Debug.Log ("brush " + Brushsize);
        TerrainLayer m_SelectedTerrainLayer = null;
        m_SelectedTerrainLayer = t.terrainData.terrainLayers[textnum]; //ссылка на слой в Инспекторе  
        Texture2D brushTexture = Resources.Load<Texture2D> (brushnames);
        Material mat = TerrainPaintUtility.GetBuiltinPaintMaterial ();
        BrushTransform brushXform = TerrainPaintUtility.CalculateBrushTransform (t, v2, Brushsize, Rotation);
        PaintContext paintContext = TerrainPaintUtility.BeginPaintTexture (t, brushXform.GetBrushXYBounds (), m_SelectedTerrainLayer);
        Vector4 brushParams = new Vector4 (0.5f, alpha, 0.0f, 0.0f);
        mat.SetTexture ("_BrushTex", brushTexture);
        mat.SetVector ("_BrushParams", brushParams);
        TerrainPaintUtility.SetupTerrainToolMaterialProperties (paintContext, brushXform, mat);
        Debug.Log ("Something");
        Graphics.Blit (paintContext.sourceRenderTexture, paintContext.destinationRenderTexture, mat, (int) TerrainPaintUtility.BuiltinPaintMaterialPasses.PaintTexture);

        TerrainPaintUtility.EndPaintTexture (paintContext, "Terrain Paint - Texture");
    }
}

Почему вовремя сохранения пропадают эти текстуры ?