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6.4

Ray OBB intersection not working. Ray not transformed into OBB space correctly?

Asked by Dr_Spankenstein in 3D Game Programming, Physics & Artificial Intelligence in Game Programming, Algorithms

Tags: Ray OBB Intersection 3D

I am trying to get a ray to return true when intersecting with an OBB. My method works sound with an AABB but when I try it with an OBB then no intersection is ever returned.

I think that I have not transformed the ray into OBB space correctly and I have attached the code to show what I have so far:

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                         float t_Min = 0.0f;
 
            // Maximum distance ray can travel (makes it a segment, otherwise it would be infinite)
            float t_Max = float.MaxValue;
 
            float ood = 0.0f;
            float t1 = 0.0f;
            float t2 = 0.0f;
 
            // Translate ray to OBB space
            Vector3 min_Local = Origin - oBB.Position;      // (P - C)
            Vector3 max_Local = Origin - oBB.Position;      // (P - C)
 
            float min_X = Vector3.Dot(min_Local, oBB.Axis_X);
            float max_X = Vector3.Dot(max_Local, oBB.Axis_X);
            float min_Y = Vector3.Dot(min_Local, oBB.Axis_Y);
            float max_Y = Vector3.Dot(max_Local, oBB.Axis_Y);
            float min_Z = Vector3.Dot(min_Local, oBB.Axis_Z);
            float max_Z = Vector3.Dot(max_Local, oBB.Axis_Z);
 
            // For all 3 slabs
            if (Math.Abs(Direction.X) < float.Epsilon)
            {
                // Ray is parallel to slab.  No hit if origin (p in book) not within slab
                if (Origin.X < min_X || Origin.X > max_X)
                {
                    return false;
                }
            }
            else
            {
                // Compute intersection t value of ray with near and far plane of slab
                ood = 1.0f / Direction.X;
                t1 = (min_X - Origin.X) * ood;
                t2 = (max_X - Origin.X) * ood;
 
                // Make (t1) be intersection with near plane, (t2) with far plane
                if (t1 > t2)
                {
                    Swap(ref t1, ref t2);
                }
 
                // Compute the intersection of slab intersection intervals
                t_Min = Math.Max(t_Min, t1);
                t_Max = Math.Min(t_Max, t2);
 
                // Exit with no collision as soon as slab intersection becomes empty
                if (t_Min > t_Max)
                {
                    return false;
                }
            }
            if (Math.Abs(Direction.Y) < float.Epsilon)
            {
                // Ray is parallel to slab.  No hit if origin (p in book) not within slab
                if (Origin.Y < min_Y || Origin.Y > max_Y)
                {
                    return false;
                }
            }
            else
            {
                // Compute intersection t value of ray with near and far plane of slab
                ood = 1.0f / Direction.Y;
                t1 = (min_Y - Origin.Y) * ood;
                t2 = (max_Y - Origin.Y) * ood;
 
                // Make (t1) be intersection with near plane, (t2) with far plane
                if (t1 > t2)
                {
                    Swap(ref t1, ref t2);
                }
 
                // Compute the intersection of slab intersection intervals
                t_Min = Math.Max(t_Min, t1);
                t_Max = Math.Min(t_Max, t2);
 
                // Exit with no collision as soon as slab intersection becomes empty
                if (t_Min > t_Max)
                {
                    return false;
                }
            }
            if (Math.Abs(Direction.Z) < float.Epsilon)
            {
                // Ray is parallel to slab.  No hit if origin (p in book) not within slab
                if (Origin.Z < min_Z || Origin.Z > max_Z)
                {
                    return false;
                }
            }
            else
            {
                // Compute intersection t value of ray with near and far plane of slab
                ood = 1.0f / Direction.Z;
                t1 = (min_Z - Origin.Z) * ood;
                t2 = (max_Z - Origin.Z) * ood;
 
                // Make (t1) be intersection with near plane, (t2) with far plane
                if (t1 > t2)
                {
                    Swap(ref t1, ref t2);
                }
 
                // Compute the intersection of slab intersection intervals
                t_Min = Math.Max(t_Min, t1);
                t_Max = Math.Min(t_Max, t2);
 
                // Exit with no collision as soon as slab intersection becomes empty
                if (t_Min > t_Max)
                {
                    return false;
                }
            }
 
            return true;

           
         

	Title
1	Cursor click on object detection
2	Restricting graphical objects to zone so…

Ray OBB intersection not working. Ray not transformed into OBB space correctly?

Asked by Dr_Spankenstein in 3D Game Programming, Physics & Artificial Intelligence in Game Programming, Algorithms

Tags: Ray OBB Intersection 3D

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