Object boundries.
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 11/05/2010 at 15:27, xxxxxxxx wrote:
User Information:
Cinema 4D Version: 11.5
Platform: Windows ;
Language(s) : C++ ;---------
How would I determine if a point in space is within the boundaries of an object?Any help with this would be greatly appreciated. Thanks.
~Shawn
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 06:08, xxxxxxxx wrote:
Use a Ray-Triangle Intersection test. Problem is that it needs to test all polygons against the point and treat each non-triangular polygon as two or more triangles.
To make the elimination process faster, start with spherical bounding test then a oriented-bounding-box (OBB) test. This will tell you quickly whether the point is even near enough to the object to consider the ray-triangle testing (which is more intensive). You might also want to look into B-trees or Oct-trees.
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 06:25, xxxxxxxx wrote:
great .. thanks for the info robert. Nice to see you again!
~Shawn
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 10:03, xxxxxxxx wrote:
Hey Robert,
Is this the type of thing I should be looking for?
http://wiki.cgsociety.org/index.php?title=Ray_Triangle_Intersection&redirect=no
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 11:56, xxxxxxxx wrote:
Optimized code is faster.
//////////////////////////////////////////////////////////////// // DIRayCollider.h //////////////////////////////////////////////////////////////// // Drop It! Pro Ray-TrianglularMesh Intersection Class include //////////////////////////////////////////////////////////////// // V0.8 2006.01.03 Robert Templeton //////////////////////////////////////////////////////////////// #ifndef _DIRAYCOLLIDER_H_ #define _DIRAYCOLLIDER_H_ // CLASS: DIRayCollider class DIRayCollider { private: Vector* points; CPolygon* poly; CPolygon* lastPoly; Matrix gmat; LVector hitpos; // Triangle Vector v0; Vector v1; Vector v2; // Ray LVector p0; LVector p1; public: DIRayCollider(); ~DIRayCollider(); void Init(BaseObject* goal); Bool Intersect(const Vector& ray_p0, const Vector& ray_p1, Real* distance); //Bool IntersectNearPoint(const Vector& ray_p0, const Vector& ray_p1, Vector* point); //Bool IntersectFarPoint(const Vector& ray_p0, const Vector& ray_p1, Vector* point); CHAR intersect_RayTriangle(const LVector& lv0, const LVector& lv1, const LVector& lv2); static DIRayCollider* Alloc(); static void Free(DIRayCollider*& data); }; #endif //_DIRAYCOLLIDER_H_//////////////////////////////////////////////////////////////// // DIRayCollider.cpp //////////////////////////////////////////////////////////////// // Drop It! Pro Ray-TriangularMesh Intersection Class include //////////////////////////////////////////////////////////////// // V0.8 2006.01.03 Robert Templeton //////////////////////////////////////////////////////////////// // Includes #include "general.h" #include "DIRayCollider.h" // METHODS: DIRayCollider ================================================================================================== // Constructor //*---------------------------------------------------------------------------* DIRayCollider::DIRayCollider() //*---------------------------------------------------------------------------* { } // Destructor //*---------------------------------------------------------------------------* DIRayCollider::~DIRayCollider() //*---------------------------------------------------------------------------* { } // DIRayCollider.Init //*---------------------------------------------------------------------------* void DIRayCollider::Init(BaseObject* goal) //*---------------------------------------------------------------------------* { PolygonObject* pobj = (PolygonObject* )goal; #ifdef C4D_R11 points = pobj->GetPointW(); poly = pobj->GetPolygonW(); #else points = pobj->GetPoint(); poly = pobj->GetPolygon(); #endif lastPoly = poly + pobj->GetPolygonCount(); gmat = pobj->GetMg(); } // DIRayCollider.Intersect // - Returns the nearest distance intersection //*---------------------------------------------------------------------------* Bool DIRayCollider::Intersect(const Vector& ray_p0, const Vector& ray_p1, Real* distance) //*---------------------------------------------------------------------------* { p0 = LVector(ray_p0.x, ray_p0.y, ray_p0.z); p1 = LVector(ray_p1.x, ray_p1.y, ray_p1.z); *distance = MAXREAL; UCHAR res; Bool intersection = FALSE; Real dist; // Get intersections, if any, and retain nearest for (CPolygon* p = poly; p != lastPoly; ++p) { v0 = gmat*points[p->a]; v1 = gmat*points[p->b]; v2 = gmat*points[p->c]; res = intersect_RayTriangle(LVector(v0.x, v0.y, v0.z), LVector(v1.x, v1.y, v1.z), LVector(v2.x, v2.y, v2.z)); if (res < 1) continue; if (res == 1) { intersection = TRUE; dist = LDistance(p0, hitpos); if (dist < *distance) *distance = dist; } else if (res == 2) { *distance = 0.0f; return TRUE; } } return intersection; } // DIRayCollider.Intersect // anything that avoids division overflow #define SMALL_NUM 0.00000001f //*---------------------------------------------------------------------------* CHAR DIRayCollider::intersect_RayTriangle(const LVector& lv0, const LVector& lv1, const LVector& lv2) //*---------------------------------------------------------------------------* { LVector u, v, n; // triangle vectors // get triangle edge vectors and plane normal u = lv1 - lv0; v = lv2 - lv0; n = u % v; // cross product // triangle is degenerate if (n == (LVector)0) return -1; // do not deal with this case LVector dir, w0; // ray vectors dir = p1 - p0; // ray direction vector w0 = p0 - lv0; LReal a, b; // params to calc ray-plane intersect a = -(n * w0); b = n * dir; // ray is parallel to triangle plane if (fabs(b) < SMALL_NUM) { // ray lies in triangle plane if (a == 0) return 2; // ray disjoint from plane else return 0; } // get intersect point of ray with triangle plane LReal r; r = a / b; // ray goes away from triangle if (r < 0.0) return 0; // => no intersect // for a segment, also test if (r > 1.0) => no intersect // intersect point of ray and plane hitpos = p0 + r * dir; // is I inside T? LVector w; LReal uu, uv, vv, wu, wv, D; uu = u * u; uv = u * v; vv = v * v; w = hitpos - lv0; wu = w * u; wv = w * v; D = 1.0 / (uv * uv - uu * vv); // get and test parametric coords a = (uv * wv - vv * wu) * D; // I is outside T if ((a < 0.0) || (a > 1.0)) return 0; b = (uv * wu - uu * wv) * D; // I is outside T if ((b < 0.0) || ((a + b) > 1.0)) return 0; // I is in T return 1; } // Static Allocator //*---------------------------------------------------------------------------* DIRayCollider* DIRayCollider::Alloc() //*---------------------------------------------------------------------------* { return gNew DIRayCollider; } // Static Deallocator //*---------------------------------------------------------------------------* void DIRayCollider::Free(DIRayCollider*& data) //*---------------------------------------------------------------------------* { gDelete(data); } -
THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 12:04, xxxxxxxx wrote:
awesome.. you are the man.
Thanks again. -
THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 16:13, xxxxxxxx wrote:
Hey Robert, I am trying to build an example based on the code you provided. All is going well except I notice you include "general.h" in your code.
I am assuming that in the line:
dist = LDistance(p0, hitpos);
LDistance is defined in general.h?
would you mind telling me what LDistance is defined as?
Can this be replaced with Len(p-p)?
Thanks a lot.
~Shawn
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 16:58, xxxxxxxx wrote:
Sorry about that. It is just a 3D point-point distance calculation:
// Return Real distance between two LVectors //*---------------------------------------------------------------------------* Real LDistance(LVector v1, LVector v2) //*---------------------------------------------------------------------------* { Real x; Real y; Real z; x = v2.x - v1.x; y = v2.y - v1.y; z = v2.z - v1.z; return (Real)Sqrt((x*x) + (y*y) + (z*z)); } -
THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 17:07, xxxxxxxx wrote:
So if I want to check if a point has intersected with the triangle I call intersect_RayTriangle
and pass it the points of the triangle in question?
~Shawn
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 17:31, xxxxxxxx wrote:
My routines are set to be initiated with a polygon object to test against but you can certainly alter it to take a point instead. In your case, I'd alter it to take the point and send the polygon object's triangles one at a time in which you want to test. Lemme see if I can attach the appropriate source file to a message.
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 17:45, xxxxxxxx wrote:
Great.. that will help a lot. Thanks again Robert.
~Shawn
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 17:54, xxxxxxxx wrote:
I have one more question.
So the first step is to call init(MyObjectThatThepoint will collide with)?Then I want to call Intersection () and pass it the point and the vector that determines the ray, what is the distance variable?
and by calling Intersection, that then calls intersect_RayTriangle to see if the intersection has happened?
and then returns the bool as to whether it has happened or not?thanks,
Shawn
so that intersection can then call
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 19:06, xxxxxxxx wrote:
Yes.
Yes.
Distance is what is returned. In my case, I'm seeking intersection of two objects so the distance counts. In your case, you should be looking to see whether 'penetration' exists - the point is inside the object.
Yes.
Yes. -
THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 19/05/2010 at 19:16, xxxxxxxx wrote:
lol.. thanks.. I guess 1 question turned in to 5.. HAHA
~Shawn