Alessandro

Members
  • Content count

    426
  • Joined

  • Last visited

Community Reputation

302 Neutral

About Alessandro

  • Rank
    Member
  1. Find vector normal to line segment

    Thanks a lot for the explanations!
  2. Hello folks, I googled around and I yet can't find a way to get this done. Suppose I have a line segment going from (x1,y1,z1) to (x2,y2,z2). How do I calculate the normal vector perpendicular to this line? Thanks for any help.
  3. STL C++: iterator issue

    Thanks a lot for all the precious hints! Changed the XCode build setting as suggested by jwezorek and using lambda functions.
  4. STL C++: iterator issue

    Hi Chris, can't do that since I need to compile on XCode too...
  5. STL C++: iterator issue

    I think I sorted it out: struct findNodeUUID2 { findNodeUUID2(int i) : id(i) { } bool operator()(const MyItem *obj) { return (obj->test==id); } int id; };
  6. Hi folks,   I'm trying to search a std::vector declared like this: std::vector<MyItem*> myNodeContainer; where MyItem is looking like this: class MyItem :public QGraphicsItem { public: MyItem(QString QwNodeType, QString iQwFamilyType); int testID; ... Now, I've built a function to search the testID: struct findNodeUUID2 { findNodeUUID2(int i) : id(i) { } bool operator()(const MyItem* &obj) { return (obj->testID==id); } int id; }; and I try to search like this: std::vector<MyItem*>::iterator findNodeIterator; findNodeIterator=std::find_if(myNodeContainer.begin(),myNodeContainer.end(), findNodeUUID2(1234) ); Linker errors as follows:   stl_algo.h.... No matching function for call to object of type 'findNodeUUID2'   What am I doing wrong? I suppose I'm using pointers the wrong way? Thanks for any suggestion    
  7. Evaluating curve points

    Hi folks, I'd like to ask help about evaluating curve points as displayed in the attached image. I'm be able to discard points if the curve is straight, comparing angles between each vector segment (left part).   I'd like to ask how could I evaluate points so that I can build a spline that passes through initial points (blue ones), and adds a number of green points where needed so that I can get a curve instead of a segmented vector.   Thanks
  8. Vector dot product

    I'm trying to use vector dot product to get the angle between two vectors, but I'm puzzled by the results.   Given two vectors, A and B: A(0.0, 0.2, 0.0) B(0.8, 0.0, 0.0) The angle between those, calculated with the dot product: alpha= (acos(A*B)) * RAD_TO_DEG properly returns 90°. Now, let's have two vectors pointing in the same direction: A(0.2, 0.2, 0.0) B(0.8, 0.8, 0.0) Would you guys explain me why in this case alpha is equal to 9.9°, while I'd expect to return 0°? Thanks    
  9. "Preventing" collision detection

    [quote name='C0lumbo' timestamp='1352970376' post='5001156'] In your function, t is the distance between point p and point c (assuming dir is normalised) So, changing "if (t > 0.00001)" to "if (t > 1.0)" would make the function ignore collisions that occur within one unit of the origin of the ray. [/quote] Thank you very much, that was successful.
  10. "Preventing" collision detection

    [quote name='SimonForsman' timestamp='1353003308' post='5001297'] To get the distance between two points(p and c) just treat them as vectors and you get: distance = ||c-p|| are you trying to prevent collision [b]detection[/b] like the post title says or are you trying to stop actors before a collision occurs ? [/quote] Actually the 2nd option would be perhaps a better option for my needs.
  11. "Preventing" collision detection

    Also, I'd like to ask if there are faster algorithms that do ray triangle intersection, or this is just the way to go.
  12. "Preventing" collision detection

    Sorry for not being more precise. Take a look at the attached image. You see there is a point [size=5][b]p[/b][/size] the is being moved in direction [size=5][i][b]v[/b][/i][/size], and the collision point [size=5][b]C[/b][/size]. I'd like to "monitor" the distance between the point [size=5][b]p[/b][/size] and the collision point [b][size=5]C[/size][/b], so that I can stop the routine before it actually collides.
  13. "Preventing" collision detection

    Sorry for not being more precise. Take a look at the attached image. You see there is a point [size=5][b]p[/b][/size] the is being moved in direction [size=5][i][b]v[/b][/i][/size], and the collision point C. I'd like to "monitor" the distance between the point [size=5][b]p[/b][/size] and the collision point [b][size=5]C[/size][/b], so that I can stop the routine before it actually collides.
  14. Hello folks, I've created a basic collision detection routine following this document: http://www.lighthouse3d.com/tutorials/maths/ray-triangle-intersection/ I'd like to monitor the distance from the point P and the triangle being tested for intersection, so that I can stop the routine when the distance falls below a certain value. I tried modifying the 0.00001 values in the code thinking that it was meant to be a tolerance value for such collision "distance", but it seems to be ineffective. What do you think? There is a way to do it? Here below is the routine derived from the document above: [code] int rayIntersectsTriangle(vector3_t orig, vector3_t dir, vector3_t v0, vector3_t v1, vector3_t v2) { float a,f,u,v,t; vector3_t e1= v1-v0; vector3_t e2= v2-v0; vector3_t h=dir^e2; a = e1*h; if (a > -0.00001 && a < 0.00001) return(false); f = 1.0/a; vector3_t s=orig-v0; u = f * (s*h); if (u < 0.0 || u > 1.0) return(false); vector3_t q=s^e1; v = f * (dir*q); if (v < 0.0 || u + v > 1.0) return(false); // at this stage we can compute t to find out where the intersection point is on the line t = f * (e2*q); if (t > 0.00001) // ray intersection return(true); else // this means that there is a line intersection // but not a ray intersection return (false); } [/code]
  15. Problem declaring extern std::vector

    Hi guys, I'm still at trouble with this. Following your suggestions, and taking a look at the initial code I posted, I made a forward class declaration like this: [code]class myTempObjects[/code]; But then how do I declare the extern vector? I tried the following and I'm getting a "incomplete type 'myTempObjects' named in nested name specifier" [code]std::vector<myTempObjects::myTempObjectLib> myTmpObject; [/code]