Dhanrajd Posted May 5, 2015 Share Posted May 5, 2015 (edited) Hello, I want to slice frustum with plane. I have frustums of various diameters and I slice them at required point slice works fine for most of my frustums, only for particular input diameter it fails and does not give any error. Please find attached dwg file. Thanks, Dhanraj Slice-Issue.dwg Edited May 5, 2015 by Dhanrajd mistake Quote Link to comment Share on other sites More sharing options...
Dadgad Posted May 5, 2015 Share Posted May 5, 2015 This is pretty strange. I got a non intersecting disclaimer a bunch of times, although that doesn't appear to be correct. I usually SLICE with a planar Object (the circle in this case), but I could not get that to work. The quadrant snaps did not seem to want to be picked up, as I tried to use them to define a 3Point slice plane, eventually got it to work that way. I won't pretend to understand it. I just went back into the drawing and tried it again, using the planar Object option and it worked fine, being the one with the pink dots on it. Odd for sure, wish I could explain it. Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 5, 2015 Author Share Posted May 5, 2015 Thanks for reply, but I dint understood it . Actually Plane i am creating with base point as (10,0,0) and X -axis as normal. Or planer geometry Circle is created at center 10,0,0 then it doesn't work. If you slightly move plane or circle from 10,0,0 (even 10.01,0,0) it works fine. I don't understand why it is not working at particular point . 3 point for plane I gave are 10,0,0 - 10,10,0 - and 10,10,10 Quote Link to comment Share on other sites More sharing options...
Dadgad Posted May 5, 2015 Share Posted May 5, 2015 If you have a circle there already, just turn on the QUADRANT osnaps, and select 3 of them with your mouse. I see no need to enter the 3D coordinates, seems tedious. I am sorry I too find it weird, wish I could explain it to you. Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 6, 2015 Author Share Posted May 6, 2015 Thanks for solution, but it will not help me as I am doing all this through lisp and objectArx so I want to understand reason for failure so that I can modify my program for such cases Quote Link to comment Share on other sites More sharing options...
Dadgad Posted May 6, 2015 Share Posted May 6, 2015 That explains why you are using coordinate entries then. Good luck with it. Lots of seriously smart forum members, hopefully somebody else will be able to understand and explain it. As you seem to be using the circle only to define the cutting plane, why is the center point so critical? As in your first post you mention specific input diameters? Quote Link to comment Share on other sites More sharing options...
SEANT Posted May 6, 2015 Share Posted May 6, 2015 How was the frustum created? ObjectARX? Quote Link to comment Share on other sites More sharing options...
Dadgad Posted May 6, 2015 Share Posted May 6, 2015 Okay, no more fooling around, here comes the A Team! Quote Link to comment Share on other sites More sharing options...
SEANT Posted May 6, 2015 Share Posted May 6, 2015 In this case, I hope the "A" in A Team doesn't mean answers; I don't know what's causing problems either. The GRIP on the cone seams weird. And the cone is mildly elliptical. Still, doesn't seam like that should be a problem. Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 6, 2015 Author Share Posted May 6, 2015 Yes , frustum is created by acis modeler api in turn objectArx, and it is elliptical . I have series of elliptical cone and the method works for all only this case is failing and code is very old so I can not simply change the slicing plane coordinates. I will post the input values for frustom. Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 6, 2015 Author Share Posted May 6, 2015 Also I am creating frustum at fix co-ordinates so, slicing plane is hard coded at 10,0,0 and x -axis as normal. For all other frustum it works fine Quote Link to comment Share on other sites More sharing options...
SEANT Posted May 6, 2015 Share Posted May 6, 2015 The 3d Solid modeler seems particularly sensitive to the quirks associated with floating point operation. Would performing the slice routine with scaled geometry, and subsequent re-scale, be an option? Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 6, 2015 Author Share Posted May 6, 2015 Thanks SEANT, This seems to work Will check for different inputs Quote Link to comment Share on other sites More sharing options...
Dadgad Posted May 6, 2015 Share Posted May 6, 2015 Would performing the slice routine with scaled geometry, and subsequent re-scale, be an option? Inspirationally devious workaround SEANT! I knew you'd come up with something. Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 6, 2015 Author Share Posted May 6, 2015 Hi SEANT, As expected scaling works for this diameter but creates same issue for frustum with other diameter, currently I tested for hard coded scaling factor of 10. May be I can try with scaling factor based on diameter. Or is there any setting in AutoCAD where I can define floating point tolerances etc which can affect slice. Quote Link to comment Share on other sites More sharing options...
SEANT Posted May 6, 2015 Share Posted May 6, 2015 If you expect to be dealing with solids at an architectural scale, I'd suggest scaling by a factor of 1000. Essentially, treating units as Meters instead of millimeters. Part of the problem, as related to floating point operations and 3d solids, is how quickly some of the secondary property values escalate. For instance, run the MASSPROP command on the frustum, and look at the magnitude of some of the returned values. Especially the Principal Moments Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 7, 2015 Author Share Posted May 7, 2015 I am working on layout diagrams mostly scale is mm or inch , tried with higher scaling factors like 100000, it works for most of cases but still there are cases which fails , As these are just surfaces MASSPROP is not valid. Quote Link to comment Share on other sites More sharing options...
SEANT Posted May 7, 2015 Share Posted May 7, 2015 . . . . As these are just surfaces MASSPROP is not valid. What are just surfaces? Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 7, 2015 Author Share Posted May 7, 2015 as MASSPROP is giving error "No solids or regions selected" I thought these are just surface no solid , but I am wrong the reason for MASSPROP error is different that I will try to find. Quote Link to comment Share on other sites More sharing options...
Dhanrajd Posted May 7, 2015 Author Share Posted May 7, 2015 as MASSPROP is giving error "No solids or regions selected" I thought these are just surface no solid , but I am wrong the reason for MASSPROP error is different that I will try to find. Could use MASSPROP, THE VALUES Are Mass: 49062369.679 Volume: 49062369.679 Bounding box: X: 35418.489 -- 36077.146 Y: 64914.275 -- 65328.765 Z: -250.714 -- 153.000 Centroid: X: 35696.529 Y: 65121.520 Z: -8.768 Moments of inertia: X: 2.081E+17 Y: 6.252E+16 Z: 2.706E+17 Products of inertia: XY: 1.141E+17 YZ: -2.802E+13 ZX: -1.517E+13 Radii of gyration: X: 65121.633 Y: 35697.045 Z: 74263.658 Principal moments and X-Y-Z directions about centroid: I: 689522537049.509 along [0.986 0.000 0.165] J: 1.802E+12 along [0.000 1.000 0.000] K: 1.811E+12 along [-0.165 0.000 0.986 Quote Link to comment Share on other sites More sharing options...
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