I have been modeling in 3D and have mad a few objects that have been successfully printed. For those models I made sure that their surface was continuous. But I'm curious if it matters. If I want to make a spiked ball, can I create a sphere and then create some cones and just move them so they intersect and stick out of the sphere, or is it better for printing to extruded out faces and make a spike from the spheres surface. I was thinkin that the printer might just calculate the "slices" needed to make sure my object was printed as a solid. Just wondering if I need to take the time model things so each piece has a continuous surface or not.
If I have understood correctly, the answer to your question is 'no'. Your example would work as long as you ensure (as you say) that the individual cones intersect with sphere. Shapeway's upload software will merge all intersecting shells, fix holes etc. Of course if you wished you could Boolean join these yourself before upload, but it's not necessary.
Both methods should lead to a printable mesh once your (or shapeways') software does a Boolean union of the sphere and intersecting cones. It would then depend on your choice of material whether the extrusion might be a bit advantageous (assuming that it provides some filleting between the ball and spike, which would be desirable for ceramics glazing and perhaps add a little stability in the case of the detail acrylics.
OK, thats what i thought . In Maya I'm having trouble doing booleans, and its taking more time to troubleshoot them than I would like. I may also try 3DS Max and see if its easier. Thanks for the replies
Shapeways backend will do the Boolean Union operation on model that touch like "shell 1 goes in to main shell 2 like 0.5 mm" , when it fails you can go to https://netfabb.azurewebsites.net/ or use meshmixer to have another go with remesh function http://www.meshmixer.com/download.html On high poly count meshes over 900.000 you rather do a remesh with meshmixer if applicable to lower the poly counts down and do boolean function on them. For checks and measurements use neftab basic here http://www.netfabb.com/downloadcenter.php?basic=1