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我们知道 3D 平面是由 3 个点构成的。现在在德尔福我使用 GLScene 有一个平面，你看不到任何任意点来创建一个平面。我的问题是如何通过 3 个给定点设置平面。根据 SO 规则，我编写了我的 TGLPlane 源代码。

  TGLPlane = class(TGLSceneObject)
  private
    { Private Declarations }
    FXOffset, FYOffset: TGLFloat;
    FXScope, FYScope: TGLFloat;
    FWidth, FHeight: TGLFloat;
    FXTiles, FYTiles: Cardinal;
    FStyle: TGLPlaneStyles;
    FMesh: array of array of TVertexRec;
  protected
    { Protected Declarations }
    procedure SetHeight(const aValue: Single);
    procedure SetWidth(const aValue: Single);
    procedure SetXOffset(const Value: TGLFloat);
    procedure SetXScope(const Value: TGLFloat);
    function StoreXScope: Boolean;
    procedure SetXTiles(const Value: Cardinal);
    procedure SetYOffset(const Value: TGLFloat);
    procedure SetYScope(const Value: TGLFloat);
    function StoreYScope: Boolean;
    procedure SetYTiles(const Value: Cardinal);
    procedure SetStyle(const val: TGLPlaneStyles);

  public
    { Public Declarations }
    constructor Create(AOwner: TComponent); override;

    procedure Assign(Source: TPersistent); override;

    procedure BuildList(var rci: TRenderContextInfo); override;
    function GenerateSilhouette(const silhouetteParameters
      : TGLSilhouetteParameters): TGLSilhouette; override;

    function AxisAlignedDimensionsUnscaled: TVector; override;
    function RayCastIntersect(const rayStart, rayVector: TVector;
      intersectPoint: PVector = nil; intersectNormal: PVector = nil)
      : Boolean; override;
    { : Computes the screen coordinates of the smallest rectangle encompassing the plane.<p>
      Returned extents are NOT limited to any physical screen extents. }
    function ScreenRect(aBuffer: TGLSceneBuffer): TGLRect;

    { : Computes the signed distance to the point.<p>
      Point coordinates are expected in absolute coordinates. }
    function PointDistance(const aPoint: TVector): Single;

  published
    { Public Declarations }
    property Height: TGLFloat read FHeight write SetHeight;
    property Width: TGLFloat read FWidth write SetWidth;
    property XOffset: TGLFloat read FXOffset write SetXOffset;
    property XScope: TGLFloat read FXScope write SetXScope stored StoreXScope;
    property XTiles: Cardinal read FXTiles write SetXTiles default 1;
    property YOffset: TGLFloat read FYOffset write SetYOffset;
    property YScope: TGLFloat read FYScope write SetYScope stored StoreYScope;
    property YTiles: Cardinal read FYTiles write SetYTiles default 1;
    property Style: TGLPlaneStyles read FStyle write SetStyle
      default [psSingleQuad, psTileTexture];
  end;
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1 回答 1

0

在 GLScene 中，一个平面是由它的位置和方向决定的，而不是直接由三个点决定的。

让我们标记点 A、B 和 C。选择 A 作为位置。矢量 AB 和 AC 的叉积将为您提供法线矢量。使用这些结果来设置平面的AbsolutePosition和AbsoluteDirection属性。

于 2015-11-09T17:05:35.363 回答