Surface intersection

[markov]

I need to find the intersection between two surfaces (resulting in a set of lines, arcs or splines), or between a surface and a line/spline/arc (resulting in a point). Is there a function in the API that would do that for me? Or a suggestion how to do it myself?

 

Thanks

Marko

[Matthew Hajicek - Singularity]

Create Curve at Intersection.

[markov]

How do I do that from a C-hook?

 

Marko

[Takashi Sato from Ai Solutions.]

surf_surf_intersect() function is undocumented,

and I don't know how to use it..

[markov]

Takashi,

 

I see what you mean. The function has too many arguments to be able to figure them out by trial and error.

 

Marko

[Pete Rimkus from CNC Software Inc.]

Oh, it isn't that bad....

 

Add this function prototype....

 

DllImpExp MC_BOOL surf_surf_intersect(

ent *surf_ent1, ent *surf_ent2,

MC_BOOL use_uvs,

p_2d input_uv1, p_2d input_uv2,

MC_BOOL do_multiples, MC_BOOL make_xyz, MC_BOOL make_nurbs,

short make_uv,

short *n_ents,

MC_BOOL *interrupted);

 

...and here's a quick description of the arguments

 

Inputs:

 

surf_ent1, surf_ent2 - ptrs to surface entities

 

use_uvs - Provide UV values on the 2 surfaces to start searching for intersections?

 

input_uv1, input_uv2 - it 'use_uvs' is TRUE, these are the UVs you want to use. Otherwise, they are not used

 

do_multiples - Look for more than one solution?

 

make_xyz - create the curve(s) at the intersection

 

make_nurbs - if 'make_xyz' is TRUE, make them as NURB curves (NB_ID), otherwise they'll be Parametric (S_ID).

 

make_uv - make 'Surface curve' entities (CONS_ID): 0 = none, 1 = on 1st surface, 2 = on 2nd surface, 3 = on both

 

Outputs:

 

n_ents - number of entities created

 

interrupted - did the user hit 'Esc'?

 

My recommendations...

 

use_uvs = FALSE

do_multiples = TRUE (unless you known there is only one)

make_xyz = TRUE

make_nurbs = TRUE

make_uv = 0

[markov]

Thanks Pete,

 

I am going to try it as soon as possible. I suppose the function stores the generated entities into the database. Any neat trick to figure out what newly created entities are? I have got a couple of ideas, none of them being to appealing.

 

Marko

[Pete Rimkus from CNC Software Inc.]

Markov,

 

I think this will do it for you...

 

 

// save off current end of database

DB_LIST_ENT_PTR old_db_end = db_end;

 

// do the intersection

surf_surf_intersect(...);

 

//get pointer to 1st new entity

DB_LIST_ENT_PTR found_ptr, d_ptr;

if(old_db_end == NULL)

d_ptr = db_start;

else

d_ptr = old_db_end->next;

 

// starting with that one, cycle through the database to look at all the new entities

ent e;

MC_BOOL succf = FALSE;

do

{

get_ent(&d_ptr, &found_ptr, &e, ALIVE_BIT, ALL_ENTITIES_MASK, &succf);

if(succf)

{

// do what you want with the new entity

:

:

}

} while(succf);

[markov]

Thanks,

 

I think I am all set for the project now.

 

Marko

[Pete Rimkus from CNC Software Inc.]

Glad to hear it...

[Jaouad]

Hi Pete,

 

I would like to use the function surf_surf_intersect( … ). I make a search about this function, the documentation doesn’t exist in C-hook SDK.

 

Where can I find all about it?

 

Thank you

 

Jaouad

[markov]

Jaouad, the documentation is this thread - Pete described all of its parameters. What exactly are you looking for?

 

Marko

[Jaouad]

Hi Markov,

 

Thank you for your reply.

 

Pete described me how to implement it.

 

I am going to try what Pete sent me.

 

Jaouad