Greendamo Posted February 20, 2012 Author Share Posted February 20, 2012 Hi Seant. What you have done is drawn it the way i have to do it at the moment and kind of fudge it. Basically the end result should be an extruded solid with the top parallel with ground and the sides perfectly in upright in Z. When you put the model in to wireframe and in plan view the lines of the extruded object will be in line with the 2D plan. If the model is correct you will be able to fit a perfect rectangle within the shape at any point and the corners of it will meet the 3D lines of the solid extrusion. Thanks. Quote Link to comment Share on other sites More sharing options...
SEANT Posted February 20, 2012 Share Posted February 20, 2012 . . . .Basically the end result should be an extruded solid with the top parallel with ground and the sides perfectly in upright in Z. When you put the model in to wireframe and in plan view the lines of the extruded object will be in line with the 2D plan. If the model is correct you will be able to fit a perfect rectangle within the shape at any point and the corners of it will meet the 3D lines of the solid extrusion. . . . . I don’t believe that is geometrically possible. The model I attached in my previous post has a top surface parallel, and sides perpendicular to the ground (based on the radial cross sections). I inserted the cyan rectangle such that its top edge was parallel to the Surface/Ground and tilted to be perpendicular to the spline’s path. The side and bottom edge of the rectangle project out from the perimeter thus can not produce sides that would be vertical in a swept solid. The reason it can be done with a constant pitch helix (as in post # 13) is that the rectangle is swept in such a way that it is not perpendicular to the path. If a section is taken from the solid such that the section plane is perpendicular to the path then it would not match the original swept object. The swept object can be compensated to allow the necessary cross section, but that can not accommodate a path with varying pitch. Quote Link to comment Share on other sites More sharing options...
Greendamo Posted February 20, 2012 Author Share Posted February 20, 2012 The side and bottom edge of the rectangle project out from the perimeter thus can not produce sides that would be vertical in a swept solid. You are correct Seant. The sides of the solid will be seen to project out, A square edge will never line up with a round! my mistake!!. But having said that, in wireframe the corner lines of the extruded shape will still line up with the 2D plan and you should still be able to fit a rectangle within the geometry. Quote Link to comment Share on other sites More sharing options...
SEANT Posted February 20, 2012 Share Posted February 20, 2012 . . . . in wireframe the corner lines of the extruded shape will still line up with the 2D plan and you should still be able to fit a rectangle within the geometry. You could if this was the geometry needed. VaryingPerpThickness.dwg Quote Link to comment Share on other sites More sharing options...
Dadgad Posted February 20, 2012 Share Posted February 20, 2012 You could if this was the geometry needed. Nicely done Seant, I can't find any way to get as close as that by sweeping it, despite numerous attempts and variations on the numerous themes and parameters. Quote Link to comment Share on other sites More sharing options...
SEANT Posted February 20, 2012 Share Posted February 20, 2012 Even though that model may produce nice rectangular sections, I don't think it works well for a handrail transition. Quote Link to comment Share on other sites More sharing options...
Greendamo Posted February 20, 2012 Author Share Posted February 20, 2012 See the drawing i attached. This is as close i can get to the results i want. I rotate the rectangle to the right pitch (30.6 in this case) then viewed in plan i rotate the rectangle on its face so that the corners line up with the 2D plan the best they can. Then i explode the rectangle, rotate with copy it to the end of the spline and loft the top and bottom with the 2D plan as the guide, extend the surfaces sides by 10mm and project the 2D plan on to them. This is the closest i can get to true handrail geometry. it don't realy matter that its in wire frame only as i export it and machine against the 2 side lines. like this.dwg Quote Link to comment Share on other sites More sharing options...
SEANT Posted February 20, 2012 Share Posted February 20, 2012 The curves in that file look to be constant pitch. The previous geometry was not constant. How would the issue illustrated below affect the top surface? Quote Link to comment Share on other sites More sharing options...
CM Hew Posted February 22, 2012 Share Posted February 22, 2012 Perhaps, the easiest way to do is by using a custom autolisp below are some forms that I have done quickly using an autolisp. The sections are created in 3D lines and Circular Curves in 3D. Quote Link to comment Share on other sites More sharing options...
Greendamo Posted February 22, 2012 Author Share Posted February 22, 2012 Hi Cm hew, That looks interesting! Im not familiar with Autolisp at all so i think it could be a route to go down. Could you explain how you have done it please? Thanks Quote Link to comment Share on other sites More sharing options...
CM Hew Posted February 22, 2012 Share Posted February 22, 2012 Hi Greendamo, I am not sure this section is appropriate for posting issues regarding autolisps. However, I would like to post the drawing which I have produced with the autolisp for your review. Have a look. SECT3D.dwg Maybe you can start first by looking into the forum - Autolisps, Visual Lisps and DCL section where issues like that can be found. Hope you find it useful. Quote Link to comment Share on other sites More sharing options...
SLW210 Posted February 22, 2012 Share Posted February 22, 2012 You can post a lisp any where it is useful. If deemed necessary a moderator will relocate. Quote Link to comment Share on other sites More sharing options...
CM Hew Posted February 24, 2012 Share Posted February 24, 2012 Hi SLW210 and Greendamo, I have posted the lisp in the forum - Autolisps, Visual Lisps and DCL section for your review. Please comment and give me your opinion. Thanks Quote Link to comment Share on other sites More sharing options...
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