merging 3d objects

[fish_4_all]

I need to merge a spline drawn extruded solid with a solid cylinder. I need a smooth transition for the base of the cylinder to the points on the rectangular part of the extruded part in blue. 

 

MY base knowledge is strong but my 3D knowledge is rusty at best. Haven't touched AutoCAD in 15+ years so a little rusty. Still drew this in less than 2 hours so not too rusty I think. I know I could draw this in 2d and then extrapolate to 3d but I want to know how to move points on a solid to the points on another a solid and make a smooth transition. If it helps this is for the tail of a plastic fishing worm. The cylinder is a small one that is not part of the main body of the worm. I figured that would work best so the points could be moved on the cylinder, if possible, to the perpendicular points on the rectangular base of the tail. 

 

I just can't get any of the points on either object to move without either the whole object moving or a plain of the object moving. Have tried exploding the cylinder still to no avail. Points move but the conversion back to a solid went wonky. Tried exploding the tail but the splines move together or when exploded down far enough the transitions were not smooth when made back into a solid. 

 

 

 

 

 

[ReMark]

So, you want to go from a circle to a rectangle.  Have you tried the LOFT command?  

[fish_4_all]

I will try that. I want to move the points of the cylinder to perpendicular points on the rectangular part of the other 3d object and have it smooth.

[ReMark]

16 hours ago, fish_4_all said:

I will try that. I want to move the points of the cylinder to perpendicular points on the rectangular part of the other 3d object and have it smooth.

That is not how the LOFT command works.  Are you at all familiar with HVAC metalwork and how transitions are made from square/rectangular to circular sections?  See example below.  What you would do is loft between a circle and a rectangle in order to achieve the smooth transition between the part shown in white and the one shown in blue in your first post.  

 

Edited February 28, 2022 by ReMark

[fish_4_all]

It worked. had to draw a circle and a rectangle of the same size and use LOFT to taper from one to the other. 

[ReMark]

Glad to hear you were successful.

[fish_4_all]

Your suggestion made it a lot easier and eliminated the frustration of trying to make the taper between 2 solids.