向高手求救getModelToEyeTransform函数

leez0301

AsdkCoordSamp::viewportDraw(AcGiViewportDraw* pV)
{
    pV->subEntityTraits().setFillType(kAcGiFillAlways);

    const int count = 3;
    AcGePoint3d verts[count];
    verts[0] = AcGePoint3d(0.0, 0.0, 0.0);
    verts[1] = AcGePoint3d(1.0, 0.0, 0.0);
    verts[2] = AcGePoint3d(1.0, 1.0, 0.0);

    // Draw model space line segment.
    //
    pV->subEntityTraits().setColor(kBlue);
    pV->geometry().polygon(count, verts);
 
    // Compute its representation in eye space.
    //
    AcGeMatrix3d mat;
    pV->viewport().getModelToEyeTransform(mat);

    for (int i = 0; i < count; i++) {
        verts.x += 0.01;
        verts.y += 0.01;
        verts.z += 0.01;
        verts.transformBy(mat);
    }

    // Display the eye coordinate equivalent of the
    // model space polygon.
    //
    pV->subEntityTraits().setColor(kGreen);
    pV->geometry().polygonEye(count, verts);

    // Convert from eye to display coordinates.
    //
    for (int i = 0; i < count; i++) {
        verts.x += 0.01;
        verts.y += 0.01;
        verts.z += 0.01;
  //verts.transformBy(mat);
    }

    // Draw the display space equivalent of the
    // model space polygon.
    //
    pV->subEntityTraits().setColor(kRed);
    pV->geometry().polygonDc(count, verts);
}

在这个函数中

pV->viewport().getModelToEyeTransform(mat);

    for (int i = 0; i < count; i++) {
        verts.x += 0.01;
        verts.y += 0.01;
        verts.z += 0.01;
        verts.transformBy(mat);
    }

有getModelToEyeTransform(mat);和verts.transformBy(mat) 起的什么作用啊？ 有人给详细解释一下吗？ 如何控制视图的？