Option for ShapeCasts to return only face normals #313

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1. atornity commented on Mar 16, 2025

   

   atornity

   on Mar 16, 2025

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   I need something like this as well for a character controller using avian.

   Unreal engine supports this, it returns the face normal which is the "most opposing" from the cast direction and exposes this as the ImpactNormal on FHitResult.

   /**
    * Normal of the hit in world space, for the object that was hit by the sweep, if any.
    * For example if a sphere hits a flat plane, this is a normalized vector pointing out from the plane.
    * In the case of impact with a corner or edge of a surface, usually the "most opposing" normal (opposed to the query direction) is chosen.
    */
   UPROPERTY()
   FVector_NetQuantizeNormal ImpactNormal;

   I think we should do the same and add it as a field on ShapeCastHit (rather than having a seperate mode as suggested) since a user might need access to both the face normal as well as the usual normal, and there's no reason to perform two casts in that case.

   There might also be times when users might want the normals of all the faces involved but I've personally never needed this myself and that would probably be more complicated to implement.

   👍React with 👍2Reacted by cndheat and Aceeri
2. ThierryBerger

   added

   C-EnhancementNew feature or requestNew feature or request

   P-High

   on Jun 13, 2025
3. ThierryBerger

   added

   questionFurther information is requestedFurther information is requested

   on Jun 27, 2025
4. ThierryBerger commented on Jun 27, 2025

   

   ThierryBerger

   on Jun 27, 2025

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   Can https://docs.rs/parry3d/latest/parry3d/shape/trait.Shape.html#method.feature_normal_at_point help with this ?

   The algorithms behind shapecasts don't always end up going through faces, which make it impractical to leak options onto ShapeCastOptions 🤔 ; it could be a bonus option not supported by all shapes, but such API is a bit unintuitive.
5. cndheat commented on Jun 27, 2025

   

   cndheat

   on Jun 27, 2025

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   Shape casts don't return a FeatureID, additionally a FeatureID cannot be guaranteed to be a Face which complicates things.
6. MinimalCpp commented on Nov 5, 2026

   

   MinimalCpp

   on Nov 5, 2026

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   #463 fixes part of this for heightfields: with HeightFieldFlags::FIX_INTERNAL_EDGES, a shape cast onto a heightfield no longer returns the normal of an internal edge between coplanar triangles; the hit's normal is projected into the normal cone of the surface around the witness point. It adds no option to ShapeCastOptions and leaves other shapes as they are.