[返回博客](/cn/blog) # BimRv SDK：创建线性尺寸标注元素

Vladyslav Vasylenko 十二月 09, 2021 [\#getting started](/cn/blog/tag/getting-started) [\#rfa](/cn/blog/tag/rfa) [\#rvt](/cn/blog/tag/rvt)

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LinearDimension 元素的目的是在两个元素之间放置尺寸（测量距离），例如：

- 参考平面
- 参考线
- 模型线
- 符号线
- 草图中的曲线
- GenSweep 中的边
- GenSweep 中的面

重要的是这些元素彼此平行。

![linear dimension](/files/inline-images/bimrv_linearDimension_2.png)以下是创建 LinearDimension 元素的示例。首先，在 CurveElem 对象和 ExtrusionElem 对象的面之间创建一个 LinearDimension 元素。

```
OdBmDatabasePtr pDb = app->readFile(L"Family2.rfa");

ODBM_TRANSACTION_BEGIN(t, pDb)
  t.start();
    OdBmGLinePtr pGLine = OdBmGLine::createObject();
    pGLine->set(OdGePoint3d(2.10358711161061, 4.59562230643384, 0), OdGePoint3d(4.65648409172057, 4.59562230643383, 0));

    OdBmGeomRefPtrArray arrGeomRefs;
    {
      OdBmGeomRefPtr pGeomRef = OdBmGeomRef::createObject();
      pGeomRef->set(pDb->getObjectId(OdDbHandle(2842))); // CurveElem
      arrGeomRefs.append(pGeomRef);
    }
    {
      OdBmGeomRefPtr pGeomRef = OdBmGeomRef::createObject();
      pGeomRef->set(pDb->getObjectId(OdDbHandle(2862)), 5); // face of ExtrusionElem
      arrGeomRefs.append(pGeomRef);
    }

    OdBmDBViewPtr pDBView = pDb->getObjectId(OdDbHandle(23)).safeOpenObject();
    OdBmLinearDimStringPtr pLinearDimString = OdBmLinearDimString::createObject();
    pDb->addElement(pLinearDimString);
    TEST_ASSERT(pLinearDimString->set(pDBView, pGLine, arrGeomRefs) == eOk);
  t.commit();
ODBM_TRANSACTION_END()
```

执行此代码后，将出现一个尺寸元素。

![bimrv linear dimension](/files/inline-images/bimrv_linearDimension_1.png)接下来，在两个 CurveElem 对象之间创建一个 LinearDimension。

```
OdBmDatabasePtr pDb = app->readFile(L"Family1.rfa");

ODBM_TRANSACTION_BEGIN(t, pDb)
  t.start();
    OdBmPlanePtr pPlane = OdBmPlane::createObject();
    pPlane->set(OdGePoint3d::kOrigin, OdGeVector3d::kXAxis, OdGeVector3d::kYAxis);
    OdBmSketchPlanePtr pSketchPlane = OdBmSketchPlane::createObject();
    OdBmObjectId sketchPlaneId = pDb->addElement(pSketchPlane);
    pSketchPlane->setGeomPlane(pPlane);

    OdBmObjectId arrRefs[2];
    {
      OdBmCurveElemPtr pCurveElem = OdBmCurveElem::createObject();
      arrRefs[0] = pDb->addElement(pCurveElem);

      OdGePoint3d start = OdGePoint3d(5, 5, 0);
      OdGePoint3d end = OdGePoint3d(5, 10, 0);

      pCurveElem->setSketchPlane(sketchPlaneId);
      pCurveElem->createLine(start, end);
    }

    {
      OdBmCurveElemPtr pCurveElem = OdBmCurveElem::createObject();
      arrRefs[1] = pDb->addElement(pCurveElem);

      OdGePoint3d start = OdGePoint3d(10, 5, 0);
      OdGePoint3d end = OdGePoint3d(10, 10, 0);

      pCurveElem->setSketchPlane(sketchPlaneId);
      pCurveElem->createLine(start, end);
    }

    OdBmGLinePtr pGLine = OdBmGLine::createObject();
    pGLine->set(OdGePoint3d(5, 5, 0), OdGePoint3d(10, 5, 0));

    OdBmGeomRefPtrArray arrGeomRefs;
    for (OdUInt8 iIndex = 0; iIndex < 2; iIndex++)
    {
      OdBmGeomRefPtr pGeomRef = OdBmGeomRef::createObject();
      pGeomRef->set(arrRefs[iIndex]);
      arrGeomRefs.append(pGeomRef);
    }

    OdBmDBViewPtr pDBView = pDb->getObjectId(OdDbHandle(23)).safeOpenObject();
    OdBmLinearDimStringPtr pLinearDimString = OdBmLinearDimString::createObject();
    pDb->addElement(pLinearDimString);
    TEST_ASSERT(pLinearDimString->set(pDBView, pGLine, arrGeomRefs) == eOk);
  t.commit();
ODBM_TRANSACTION_END()
```

![bimrv linear dimension](/files/inline-images/bimrv_linearDimension_3.png)

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