The actor launch a projectile. At impact point I’d like to calculate points A & B placed on a line oriented by 90 degrees.
I can rotate at the impact point by 90 degrees, but I have no idea how to calculate point A and B.
FVector Distance(Radius, 0.0f, 0.0f);
FVector VertexDir = Distance.RotateAngleAxis(90.0f, FVector(0.f, 0.f, 1.f));
FVector Location = ImpactLocation + VertexDir;
Radius is the distance between impact point and A or B.
You’ve got your vertexDir as the direction impact to A (or B) already, and the distance between A and B is your radius, thus the distance from your impact point to either point is radius/2, therefore the length for VertexDir must be radius/2. The location than is ImpactLocation + radius/2 * VertexDir (assuming that your vertexdir is normalized)
Thank you very much for your help. It is working.
Have a nice day.
Please feel free to mark my answer as correct 
