Fusion
I don't know if the original problem has been solved by the @Anonymous but I guess this may be useful for someone else who is struggling to use the Surface environment in Fusion. I think that there are too few people out there who advocate the use of Project >Intersection Curve for surface modelling and it is leading people to use Solid > Create Form or 3D sketching techniques which though useful are unnecessary and sometimes tortuous. The original model included by @Anonymous is a perfect example of this, the timeline is long, unrepairable and undecipherable. I don't mean any disrespect by this, it is creditworthy to have the tenacity to get so far, but for me it is indicative of how easy it is to start using Fusion 360 without understanding how important and useful some of the core principles of 3D modelling are.
I would also like to thank @TrippyLighting for his interest in this thread because kudos from experienced Fusion 360 users is encouraging and in the absence of interest from anyone else the only reason to document this.
This screencast is a general overview of the method and is designed for people who are new to Fusion 360. Apologies to anyone who knows all this stuff already. If anyone less experienced would like more details I would be happy to answer any questions.
1. The screencast at 0.05 shows the inclusion of a canvas, Mask A using Insert > Attached Canvas. This is a print screen of the original model from the front view which for some reason I put the YZ plane hence the Right view on the view cube, apologies for that. The canvas can be calibrated by right clicking on the canvas in the browser placing two reference points and entering the desired distance. See https://knowledge.autodesk.com/support/fusion-360/learn-explore/caas/video/youtube/watch-v-zDlWwSN54b8.html?st=attach%20canvas
2. I copied the calibration measurement using Cntrl+C and attached another canvas (Mask B) on the XZ plane using the copied measurement from step 1 to make both canvasses the same (0.45). You will have to use Cntrl + V to paste as there is no right-click menu in the calibration tool.
3. At 0.57 you can see that I have created a sketch on the XZ plane called Layout A. This sketch is designed to show the principle underlying the projection of 3D geometry. For Project > Intersection Curve to work properly with surface modelling tools such as patch and loft, the start and end points of the two curves that you are using to make an intersection curve must be planar. More on that later. You can see in this sketch (1.07) that I have placed the endpoints of construction lines which are perpendicular to the YZ plane on the points in the canvas that correspond to the vertices on the original model canvas, this is obviously to make the model the same size and shape as the original however their position is not critical.
4. At 1.19 I have demonstrated another sketch on the XZ plane called Front (which technically should be called Right or Side). I have used only Sketch > Spline > Control Point Spline in this model and sketched out the hard (creased?) edges of the model. The end points of the splines need to be coincident with the end points of the horizontal lines in Layout A.
5. At 1.26 you can see that I have added a Horizontal Constraint to the control point line on either side of this particular spline. This is important because sometimes you will have to use two splines to make one curve if one spline will not produce a contiguous intersection curve, doing this will mean that the point at the top of this curve is the highest point in the spline. I have not recorded this because this is just an overview but it is a subject worth revisiting.
6. At 1.44 I am showing the second profile sketch on the YZ plane called Right. This sketch should contain the curves of your hard edges using splines as before but you must project into this sketch the endpoints of the horizontal construction lines in Layout A and use a horizontal constraint between the end points of those lines that correspond to the same point in the sketch called Front. I have tried to demonstrate this at 2.16 to 2.25. Making corresponding spline points from the Right and Front sketches horizontal to each other is important, if they are not horizontal they are not coplanar and you will not have a closed 3D profile with which to create a surface. This point may also will need further explanation.
7. At 2.34 I have shown another sketch called Intersection Curve. This sketch contains all the projections between the corresponding splines in the sketch called Front and the one called Right. To produce this geometry use Sketch > Project > Intersection Curve and select a curve from Front and the corresponding curve from Right.
There is no need to project the intersection of curves on outer splines of the sketch called Front because those splines are already coplanar with the XZ plane (see arrow).
8. From there you can patch away. If your intersection geometry is ok the patch will work straight away. If it does not allow you to select one of the lines in the profile in which you wish to patch or the patch fails, the chances are there is something wrong with the Right or Front sketches and you can go back in the timeline and fix those sketches. It will almost always be because points that you think are properly constrained are not. This will need further discussion for beginners I suspect.
9. If you want create a Mirror for the other side you can do so by using Surface > Create > Mirror and you can select the Patch features in the timeline.
I hope that this makes sense to someone. These things are not always easily explained and take some time to document which is why I think this subject is not so often discussed. I have tried my best to give an insight into this process without boring anyone too much. I hope that @Anonymous or someone else looking to learn more about intersection curves will be interested enough to add to this or ask questions.
Screencast will be displayed here after you click Post.
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