NewtonWorldRayCast

[armokal]

I would like to cast a ray and find the closest hit point and NewtonWorldRayCast seems to be what I need except I'm not sure about the required callback.

void NewtonWorldRayCast(
const NewtonWorld* newtonWorld,
const dFloat* p0,
const dFloat* p1,
NewtonWorldRayFilterCallback filter,
void* userData,
NewtonWorldRayPrefilterCallback prefilter)

How do I find out what is the closest hit point? I would also like to know what is the normal vector. Is it also possible to know which polygon was hit on the particular BODY in question?
The first 2 are more important.

[martinsm]

Have you at least read documentation of NewtonWorldRayCast function?
Remarks section there explains how to find closest body that ray intersects.
Also page on NewtonWorldRayFilterCallback function shows few cases how to do implement callback function.

[armokal]

I had read the SDK documentation and this http://www.runehunter.phpnet.us/NewtonHelp.html
but didn't get what I should do.
Thanks for the link.

[JulBaxter]

I wonder why NewtonWorldRayFilterCallback calls during a NewtonWorldRayCast are ordered from end to begin ray ?

[Julio Jerez]

in a loose way teh are ordered from begin to end.

bacisally raycast scan the mutigrid cell, each laye is scaned for begion to end, but if a cell have more tan one body, it will scane then at randon.

if you fiter you must controll the order by collecting the t value and returning the value if you do not want object beyond the corrent time to be tested.
doing that speed up raycasting significanlly when you only want the first ray teh object hit.

if you return 1.0 or larger in the filter than the ray cast will continue be called for all object the ray hit.

[JulBaxter]

Humm. Ok

So if I want all bodies from begin to end(ordered), I must return 1 and sort bodies according their T ?

[Julio Jerez]

yes that is correct. But remenber the will not be perfect sorted, they will be loselly sorted.
if you want then sorted form begin to end, you can make on one pass insertion sort, in the filter callbak
basically it is something like this

Code: Select all

int count = 0
float times[n];
body* bodyarray[n];
float filter (time, body, ...)
{
  // do teh filter stuff
  ...

   int i;
   for (i = count; (i > 0) &&  times[i - 1] < time; i --) {
      times[i] = times[i - 1 ];
      bodyarray[i] = bodyarray[i - 1];
  }
  times[i] = time;
  bodyarray[i] = body];
  count ++;


return 1.0
 }

[JulBaxter]

Ok. Thank you for this clarification.