3D Interoperability

[ssv]

Hello all!

I have quite superficial knowledge of SAT format, and need your help to understand some basic things.

My purpose is to translate geometry of variable-radius blend specified by srf_srf_v_bl_spl_sur entity into OpenCascade representation. As far as I understand, I need to use the following data from this entity:

1. Path curve. This is a trajectory of rolling ball's center, and it is clear enough;

2. Radius curves (left and right). Could you please explain, how this radius curve is parameterized? In my case, the radius curve is a spline with the following control points:

(0.5; 0.0), (0,5; 1), (0.25; 2), (0.25; 3).

I see that the first co-ordinate of each point is the actual radius value, but what is the second coordinate (0, 1, 2, 3)? Is it a parameter value along the path curve? Or perhaps it is just some index, e.g. of the spline's knot?

3. Left & right support surfaces. It is also clear enough;

The most shadow point for me is whether I should use the summary information from the surface?

It is summary_bs3_surface entity storing some parameterization range for the resulting blending surface. However, I'm not sure if I should use this entity, should I?

If so, how should I treat its parameter range? What is its purpose? Is it a range to trim the path curve? If not, what parameter range should I use for the path?

This is a part of the corresponding SAT file:

====================
Data:
{ srfsrfblndsur
    @11 blendsupsur
    cone 25.57986886240683 76.46210413625083 104.6759227659505

2.391828609797854e-015 -9.940116728674213e-016 -1 26.5435801570486 -

16.49244834602599 7.98813805962043e-014 1 I I -0 -1 31.25 forward I I I I
    null_curve
    nullbs 0 0 0
    @11 blendsupsur
    plane -0.9637113137161646 110.2170608866749 90.4106376879018 -

2.391828609797854e-015 9.940116728674213e-016 1 1 1.104962924977637e-009

2.391828608699508e-015 reverse_v I I I I
    null_curve
    nullbs 0 0 0
    intcurve forward { ref 1380 } I I 0 0 single_radius
    functional calibrated 6.000488053078942e-016 0.4489697612296943
    nubs 3 open 2
    6.000488053078942e-016 3 0.4489697612296943 3
    0.5 0
    0.5 1
    0.25 2
    0.25 3
    circular F 0 F 1 I I 1 -1 0.001616437402215462 1
    summary 2 0 1 9 -0.1450850689040772 -0.1088138016564395 -

0.07254253440880179 -0.03627126716116408 8.647363380909212e-011

0.03627126733411135 0.07254253458174906 0.1088138018293868 0.1450850690770245
    0.001616437402215462 OPEN OPEN NON_SINGULAR NON_SINGULAR
    0
    0
    0
    0
    0
    0
    null_curve convex rb_envelope }
====================

I will appreciate your help a lot as I haven't found any exhaustive specification of blend representation in SAT files.

Sergey.

[ssv]

After some looking around, I see that the radius function is specified via var_rad_functional entity in my case. It references the bs2_curve_def entity with the tricky control points (as described above), and a paramater range. As I understand, the latter range is the best candidate to trim the path curve of the rolling ball, as the radius function is specified on the path. However, what about information from summary_bs3_surface? It also has a parameter range, and that range is different from the radius range. How should I choose a parameter range for the path curve?

Could you please shed light on all these parameters and their meaning?

[ybiyani]

Hello ssv,

We recommend that you license ACIS to read and write into SAT format and that should address all the questions raised here as we will handle that for you. With InterOp we provide a Connect SDK to enable reading and writing from any formats that we do not support.

Regards,

Yogesh