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--- 1.0.0:pathfinding [2023/03/01 10:25] – [Setup] admin
+++ 1.0.0:pathfinding [2023/03/21 15:34] (current) – [Click to Start Pathfinding] admin
@@ Line 155: / Line 155: @@
 Image1.Bitmap.Assign(FVerifyBmp);
 </file>
+===== Click to Start Pathfinding  =====
+Many developers may struggle with the question how to combine the setup above with user interaction.
+Speaking for a classic Point & Click Adventure, a recommend way is to add a simple plane (TPlane, TGorillaPlane) for click detection.
+All other 3D elements should be set to HitTest = false, to not disturb mouse interaction with the helper plane.
+We then register a MouseUp event on the viewport, where we put all of our mouse handling.
+<file pascal>
+var
+  FDestPoint : TPoint3D;
+procedure TForm1.GorillaViewport1MouseUp(Sender: TObject; Button: TMouseButton;
+  Shift: TShiftState; X, Y: Single);
+var LRayPos,
+    LRayDir : TPoint3D;
+    LHitPos,
+    LNormal,
+    LScreenPos : TPoint3D;
+begin
+  // 1) Get 3D position of click, by converting screen coordinates into 3D coordinates
+  LScreenPos := GorillaViewport1.ScreenToWorld(PointF(X, Y));
+  // 2) Cast a ray from camera to the clicking position, to retrieve the real
+  //    3D destination coordinate
+  LRayPos := GorillaCamera1.AbsolutePosition;
+  LRayDir := (LScreenPos - LRayPos).Normalize();
+  if GorillaPlane1.RayCastIntersect(LRayPos, LRayDir, LHitPos, LNormal) then
+  begin
+    // If raycasting was successfully - we can start store the point hit by the ray
+    FDestPoint := LHitPos;
+    FDestPoint.Y := 0;
+    // Aftwards we start pathfinding
+    UpdatePathfinding();
+  end;
+end;
+procedure TForm1.UpdatePathfinding();
+var LAgentPos : TPoint3D;
+begin
+  // Get the agent position (pathfinding moving object)
+  LAgentPos := GorillaModel1.AbsolutePosition;
+  // Compute the path from 3D position - this will generate our new walking path
+  FPathFinder.FindPath(LAgentPos, FDestPoint);
+  // Stop the current animation
+  FPathAnim.Stop();
+  FPathAnim.Enabled := false;
+  // Apply computed path data to our existing TGorillaPath3D instance, instead for recreating each time
+  FPathFinder.ApplyToPath3D(FPath);
+  // Reset the used path data in our path animation
+  FPathAnim.Duration := FPath.Path.GetLength;
+  FPathAnim.Path := FPath.Path;
+  // For correct rotation of our character, we need the polygon to detect the
+  // next node to adjust to -
+  // NOTICE: READ THE SECTION BELOW
+  FPath.Path.FlattenToPolygon(FPolygon);
+  // Restart movement on path
+  FPathAnim.Enabled := true;
+  FPathAnim.Start();
+end;
+</file>
+===== Auto-Rotate an animated character =====
+<file pascal>
+procedure TForm1.FormCreate(Sender: TObject);
+begin
+[...]
+  // Register callback events
+  FPathAnim.OnProcess  := DoOnPathAnimProcess;
+  FPathAnim.OnFinish   := DoOnPathAnimFinished;
+  // For correct rotation of our character, we need the polygon to detect the
+  // next node to adjust to
+  // NOTICE: If the path changes, this has to be called again!
+  FPath.Path.FlattenToPolygon(FPolygon);
+end;
+procedure TForm1.DoOnPathAnimProcess(ASender : TObject);
+  function GetKeyValues(APolygon : TGorillaPolygon3D; const T : Single;
+  out P1, P2 : TPoint3D) : Single;
+  var LDeltaPos : Single;
+      LSglEnt : Integer;
+  begin
+    if System.Length(APolygon) <= 0 then
+    begin
+      P1 := TPoint3D.Zero;
+      P2 := TPoint3D.Zero;
+      Exit;
+    end;
+    // get current key position
+    LDeltaPos := T * High(APolygon);
+    // key value
+    LSglEnt := Floor(LDeltaPos);
+    // key offset
+    Result := LDeltaPos - LSglEnt;
+    // key coordinate
+    if (LSglEnt <= High(APolygon)) then
+      P1 := APolygon[LSglEnt]
+    else
+      P1 := APolygon[High(APolygon)];
+    inc(LSglEnt);
+    if (LSglEnt <= High(APolygon)) then
+      P2 := APolygon[LSglEnt]
+    else
+      P2 := APolygon[High(APolygon)];
+  end;
+var dx, dz  : Single;
+    LAngleY : Single;
+    P1, P2  : TPoint3D;
+begin
+  // Get the currently relevant point to compute rotation
+  GetKeyValues(FPolygon, FPathAnim.NormalizedTime, P1, P2);
+  dx := P2.X - P1.X;
+  dz := P1.Z - P2.Z;
+  LAngleY := arctan2(dx, dz);
+  GorillaModel1.RotationAngle.Y := RadToDeg(LAngleY);
+  GorillaModel1.AnimationManager.PlayAnimation('run-forward.dae');
+end;
+procedure TForm1.DoOnPathAnimFinished(ASender : TObject);
+begin
+  GorillaModel1.AnimationManager.PlayAnimation('idle.dae');
+end;
+</file>
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