//重载点描述，使它渲染时产生偏移
public override void DrawImmediateModeVertex(Vector position, Color color, Point uvs)
{
Gl.glColor4f(color.Red, color.Green, color.Blue, color.Alpha);
Gl.glTexCoord2f(uvs.X, uvs.Y);
Gl.glVertex3d(position.X+dx, position.Y+dy, position.Z+dz);
}
//更改坐标后，整个顶点序列都要改变(z轴是否也需要变化)
public void SetPosition(Vector position)
{
InitVertexPosition(position, GetWidth(), GetHeight());
}
//顶点处理
public virtual void DrawImmediateModeVertex(Vector position, Color color, Point uvs)
{
Gl.glColor4f(color.Red, color.Green, color.Blue, color.Alpha);
Gl.glTexCoord2f(uvs.X, uvs.Y);
Gl.glVertex3d(position.X, position.Y, position.Z);
}
//初始化顶点（根据一个中心点）
public void InitVertexPosition(Vector position, double width, double height)
{
double halfWidth = width / 2;
double halfHeight = height / 2;
//Clockwise creation of two triangles to make a quad.
//TopLeft , TopRight, BottomLeft (顺时针方向)
_vertexPositions[0] = new Vector(position.X - halfWidth, position.Y + halfHeight,
position.Z);
_vertexPositions[1] = new Vector(position.X + halfWidth, position.Y + halfHeight,
position.Z);
_vertexPositions[2] = new Vector(position.X - halfWidth, position.Y - halfHeight,
position.Z);
//TopRight , BottomRight , BottomLeft
_vertexPositions[3] = new Vector(position.X + halfWidth, position.Y + halfHeight,
position.Z);
_vertexPositions[4] = new Vector(position.X + halfWidth, position.Y - halfHeight,
position.Z);
_vertexPositions[5] = new Vector(position.X - halfWidth, position.Y - halfHeight,
position.Z);
}