Our part "particle" primitive is a misnomer (that we need to rename). It
should be called a "pill" primitive as it's a lozenge shape with a cylinder
capped by two hemispheres. The volume would be: vol_small_cap/2 +
vol_big_cap/2 + vol_cyl
For the case where the ends are equal size, that'd be something like ( 4/3 * PI
* r^3 / 2 ) + ( 4/3 * PI * r^3 / 2 ) + (PI * r^2 * h) which reduces to (4/3 *
PI * r^3) + (PI *r^2 * h)
At a glance, it looks like you're calculating something close, but different --
at least for volume?
Cheers!
Sean
On Jul 6, 2012, at 12:25 AM, crdueck wrote:
> Hi Wu,
>
> could you clarify that please? this link
> (http://brlcad.org/wiki/BRL-CAD_Primitives#part) states that a particle is
> defined by either a circular frustum or a circular cylinder with two
> hemispheres on each end.
>
> On 07/06/2012 12:15 AM, phoenix wrote:
>> Hi,
>> I doubt whether the part primitive is defined in that way. If you raytrace
>> it, you will find it slightly different from what you see from the draw
>> command.
>>
>> Cheers!
>> Wu
>>
>> ------------------ Original ------------------
>> From: "crdueck"<crdu...@users.sourceforge.net>;
>> Date: Fri, Jul 6, 2012 08:09 AM
>> To: "brlcad-commits"<brlcad-comm...@lists.sourceforge.net>;
>> Subject: [brlcad-commits] SF.net SVN:
>> brlcad:[51436]brlcad/trunk/src/librt/primitives/part/part.c
>>
>> Revision: 51436
>> http://brlcad.svn.sourceforge.net/brlcad/?rev=51436&view=rev
>> Author: crdueck
>> Date: 2012-07-06 00:09:14 +0000 (Fri, 06 Jul 2012)
>> Log Message:
>> -----------
>> added rt_part_volume() and rt_part_surf_area()
>>
>> Modified Paths:
>> --------------
>> brlcad/trunk/src/librt/primitives/part/part.c
>>
>> Modified: brlcad/trunk/src/librt/primitives/part/part.c
>> ===================================================================
>> --- brlcad/trunk/src/librt/primitives/part/part.c 2012-07-05 22:35:00 UTC
>> (rev 51435)
>> +++ brlcad/trunk/src/librt/primitives/part/part.c 2012-07-06 00:09:14 UTC
>> (rev 51436)
>> @@ -1813,6 +1813,56 @@
>> }
>>
>>
>> +/**
>> + * R T _ P A R T _ V O L U M E
>> + */
>> +void
>> +rt_part_volume(fastf_t *vol, const struct rt_db_internal *ip)
>> +{
>> + fastf_t vrad, hrad, mag_h;
>> + struct rt_part_internal *pip = (struct rt_part_internal *)ip->idb_ptr;
>> + RT_PART_CK_MAGIC(pip);
>> +
>> + vrad = pip->part_vrad;
>> + hrad = pip->part_hrad;
>> + mag_h = MAGNITUDE(pip->part_H);
>> +
>> + if (EQUAL(vrad, hrad)) {
>> + *vol = M_PI * vrad * vrad * (4.0/3.0 * vrad + mag_h);
>> + } else {
>> + fastf_t vrad3, hrad3, mid_section;
>> + vrad3 = vrad * vrad * vrad;
>> + hrad3 = hrad * hrad * hrad;
>> + mid_section = M_PI * mag_h * (hrad * hrad + vrad * vrad + hrad *
>> vrad) / 3.0;
>> + *vol = 2.0/3.0 * M_PI * (vrad3 + hrad3) + mid_section;
>> + }
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