9 Replies Latest reply on Aug 29, 2018 10:59 AM by Michael Baycura

    Splines are extruding with poor curve quality

    Michael Baycura

      My splines are extruding with horrible quality even though other features with more complex curves extrude fine. The curvature of the sketches are smooth and clean and the preview of the extrusion is smooth and clean, however the resulting solid is blocky. These defects are part of the actual solid model and remain when saved as another type of solid file like STL, so it's a problem affecting the usability of the model, not just a screen visualization issue. I can get the model to look better by un-merging the feature and making it a separate body, but I would prefer not to do this. I've maxed out the image quality settings and that hasn't seemed to change anything at all. I use a different feature to extrude the sine wave and the spline but i've also tried it as a single extrusion and it has the same poor blocky curvature.

      This is how it looks if i merge the extrusion, notice the poorly extruded section between straight pads and sine wave.

      This is how it looks if I choose to make it a separate body.

      Merged feature with good preview and bad result

      The sketches are all in good shape and all shared edges between features are identical, converted from the same original sketch or feature edges. At the moment i can't share the model, but maybe some folks will have some suggestions or have seen something like this before and know a way around or to fix it.

        • Re: Splines are extruding with poor curve quality
          Paul Salvador

          Hello Michael,..  can you at least copy/paste the a single wave.. that is, the spline and sine wave into another blank file and extrude onto a plate?..    otherwise, what is the unit/scale are we looking at... some measurements, such as width/height of the wave?

          ..other thoughts..

          ..is the spline normal to the sine wave.. so the thickness is equal?

          ...system image quality?

            • Re: Splines are extruding with poor curve quality
              Michael Baycura

              Here's a model with just the portion i'm talking about.

              It is working with rather extreme scales. Features sizes are in tenths of a mm while the overall model is hundreds of mm long. The board is around 480mm x 5mm and the widths and height of each wavy rib in the pictures are .1mm (1/10 of a mm if that decimal is hard to see). The waves are rendering just fine at the same scale and the splines render fine when extruded as a separate body so it seems weird the solid feature is having trouble. Though perhaps each body gets its own scale.

                • Re: Splines are extruding with poor curve quality
                  Matt Lombard

                  Paul asked about your image quality setting. That's probably what's going on here. The geometry is just fine, but the display is a little approximate. Especially stuff with weird aspect ratios going on, like yours. Tools>System Options>Document Properties>Image Quality the Shaded and Draft Quality HLR/HLV Resolution slider is probably going to have to be all the way to the right to make your parts look good. Of course, your computer will start to run a lot slower with that setting.

                  • Re: Splines are extruding with poor curve quality
                    Paul Salvador

                    Michael,.. as Matt Lombard  has said... unfortunately,.. you are sol.. the relative small feature size 0.1mm to a 480mm feature.. is forcing you to MAX out the image quality,.. yeah, (image attached)... ouch.

                    Anyhow.. this is only visual, the curve/math is find.

                    qualty.png

                      • Re: Splines are extruding with poor curve quality
                        Michael Baycura

                        Thanks everyone for taking a look.

                        I'm not completely convinced this is an image quality issue, though i know i'm pushing extreme ranges. One reason is that I tried several different image quality settings from low to high so i could see what was affected and I didn't see any change better or worse in the spline extrusion defects. I tried to make sure it was re-rendered but maybe it was always holding the highest setting view.

                        Also if it's just a display image problem i wouldn't expect to see it effect the solid model itself, unless screen quality dictates the resolution of the math underneath. The image defects are being exported as solid geometry defects when i save as STL.

                        Finally, i don't see the same geometry image defects on the way more complex cosine extrusions that are at the same settings or when i uncheck the "merge" box in the feature settings and make the spline extrusion a new body instead of a merged feature.

                         

                        All that said I'm of agreement this is likely a system/software limit issue due to working with such large feature size differences.

                          • Re: Splines are extruding with poor curve quality
                            Frederick Law

                            You can also try changing graphic card 3D setting for higher quality image.

                            This will slow SWX down.  So change it back when you finish.

                            This is setting for nVidia:

                            Most important is antialiasing-Mode and Setting.

                            If you got a Quarto card, you'll have more options.

                            The 8X means it'll render the screen at 8x higher resolution than your display then reduce it to display resolution for display.

                            You might need to restart SWX to get the setting updated.

                            nv1.jpg

                            nv2.jpg

                        • Re: Splines are extruding with poor curve quality
                          Dan Pihlaja

                          What if you make it at 10x scale....then scale it down once you are done?  Try that?

                      • Re: Splines are extruding with poor curve quality
                        John Stoltzfus

                        Michael Baycura wrote:

                         

                        My splines are extruding with horrible quality even though other features with more complex curves extrude fine.

                         

                        Completely agree that splines are tough to work with...  Why do you use splines?  Why not use arcs and lines? You'll get a much better "Look" and a sketch that is easy to change without losing the image quality, try to change or move your spline around..

                          • Re: Splines are extruding with poor curve quality
                            Michael Baycura

                            You're right, I can probably use arcs and lines in this case where i'm using a different model for different major configurations. However, originally this model was developed to work with a wide range in the number of waves and spacing across different overall widths. The spline section of the curve is a transition between a portion of the curve that has a fixed spacing to a portion that has spacing that changes from smaller to larger than the fixed side. So as configurations were changing sometimes the horizontal tangency where the spline portion meet the other line segments of the curve was inverting. Arcs were having trouble regenerating under these conditions because they don't like to flip the direction of curvature. Whereas, I found using a spline with only two points as end points and then setting the end curvature handles to be parallel to the other curve segments interfacing angle (or in other words making all the line segments tangent to the spline segment) was much more robust to dimensional changes across configurations with minimal demand on constraints or strict dimensions in the curve itself which are always changing between configs but not critical to function.

                             

                            I have also tried just moving the spline curvature slightly at different points to make it rebuild the shape slightly differently but that was really hit or miss and a very manual iteration toward a better looking defect that has to be redone when changes are made. So far the easiest solution has been to make the spline portion of the extrusion colinear but not overlap any other features and make it an unmerged feature which allows me to keep the flexibility of a spline while also providing clean geometry.