(Suggestion) Viewport.TransformHit with MaxDistance

1

At this moment Viewport.TransformHit returns an object (or nil) no matter how far the transform is. I know the MouseRayHit gives us the distance & the object, however TransformHit is more universal - it’s also encouraged inside the FPS game template.

Of course every developer who doesn’t want an infinite range can write the appropriate code, but it will be actually a copy / paste of TransformHit. We have the code already, it only needs to be distance-aware with just one if clause.

So my suggestion is to either add an overloaded TransformHit, or - like below - just add an optional MaxDistance: Single = 0 argument. In that way it’ll keep backward compatibility.

function TCastleViewport.TransformHit(const Position: TVector2;
  const ContainerCoordinates: Boolean; MaxDistance: Single = 0): TCastleTransform;
var
  RayOrigin, RayDirection: TVector3;
  RayHit: TRayCollision;
begin
  PositionToRay(Position, ContainerCoordinates, RayOrigin, RayDirection);
  RayHit := CameraRayCollision(RayOrigin, RayDirection);
  if RayHit <> nil then
  begin
    try
      Result := RayHit.Transform;

      // colossal change to the code is here:
      if (MaxDistance > 0) and (RayHit.Distance > MaxDistance) then
        Result := nil;
      // and that's it

    finally FreeAndNil(RayHit) end;
  end else
    Result := nil;
end;

Maybe it’s not a most requested feature, but I thought it could be useful.

2

Adding MaxDistance to ray-casting routines makes sense,

  • it is sometimes useful (some game-related raycasts, like “does shooting this weapon → hit a creature?” or “is visibility of something not obscured?”, have a natural “max distance”, because weapons have max range, sight has max distance).
  • and it potentially allows for optimization. Collision routine could actually stop searching when it’s certain that no collision occurs within the given distance. This optimization is not used by current CameraRayCollision underneath, but it is used by PhysicsRayCast, which we will encourage more in the future.

So, thank you, committed: Add MaxDistance to TCastleViewport.TransformHit · castle-engine/castle-engine@e9cbd3e · GitHub

Note: I plan to introduce a better “what was hit” API. The unfinished work is on hit-api-upgrade. This addresses a few things (makes physics the default, and returns a simpler type to use in various situations). I added to TODO to add MaxDistance support to that new API from the start, following arguments above, MaxDistance is a good idea.

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