C++ DirectX 9'；在顶点缓冲区更改数据时绘制线

我试图画一条线，线的起点或终点随时间变化（即每帧都有新的位置），但它不起作用

我使用

D3DUSAGE_WRITEONLY | D3DUSAGE_DYNAMIC

创建了顶点缓冲区，并将池设置为

D3DPOOL_DEFAULT

，但在更改顶点时它不会显示任何内容

事实上，只有当缓冲区内的顶点数据不变时，才会显示和绘制该线。有人能告诉我有什么问题吗

以下是我得到的代码：

Line.h

#include"Mesh.h"

class Line : public Mesh
{
public:
    Line(D3DCOLOR color, D3DXVECTOR3 startPoint, D3DXVECTOR3 endPoint);
    virtual ~Line();

    void SetPoints(D3DXVECTOR3 startPoint, D3DXVECTOR3 endPoint);

    void Draw();
};

Line.cpp

#include"Line.h"

Line::Line(D3DCOLOR color, D3DXVECTOR3 startPoint, D3DXVECTOR3 endPoint) : Mesh()
{
    vertexCount = 2;
    vertices = new VERTEX[vertexCount];

    VERTEX vertex;
    vertex.position = startPoint;
    vertex.color = color;
    vertices[0] = vertex;

    vertex.position = endPoint;
    vertex.color = color;
    vertices[1] = vertex;

    DirectX::device->CreateVertexBuffer(sizeof(VERTEX) * vertexCount, D3DUSAGE_WRITEONLY | D3DUSAGE_DYNAMIC, VERTEXFORMAT, D3DPOOL_DEFAULT, &vertexBuffer, NULL);

    VOID* vertexLocking;
    vertexBuffer->Lock(0, 0, (void**)&vertexLocking, 0);
    memcpy(vertexLocking, vertices, sizeof(VERTEX) * vertexCount);
    vertexBuffer->Unlock();
}

Line::~Line()
{

}

void Line::SetPoints(D3DXVECTOR3 startPoint, D3DXVECTOR3 endPoint)
{
    vertices[0].position = startPoint;
    vertices[1].position = endPoint;

    VOID* vertexLocking;
    vertexBuffer->Lock(0, 0, (void**)&vertexLocking, D3DLOCK_DISCARD);
    memcpy(vertexLocking, vertices, sizeof(VERTEX) * vertexCount);
    vertexBuffer->Unlock();

}

void Line::Draw()
{
    UINT passNum = 4;
    DirectX::currentShaderEffect->Begin(&passNum, 0);
    DirectX::currentShaderEffect->BeginPass(4);

    DirectX::device->SetStreamSource(0, vertexBuffer, 0, sizeof(VERTEX));
    DirectX::device->SetVertexDeclaration(DirectX::vertexDec);
    DirectX::device->DrawPrimitive(D3DPT_LINELIST, 0, 1);

    DirectX::currentShaderEffect->EndPass();
    DirectX::currentShaderEffect->End();
}

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你是如何改变点的位置的，你能粘贴代码吗？