I'm afraid that my explanation yesterday may have done more to confuse than inform. I will address this in the following post. Now, I will tell you why this model can't be turned into a 'solid'. I made this model for display only; for example, to render as you did. This model will be changed for 3D printing and casting. For example, if you look, you will see that the screw holes have no bottoms! Obviously, that won't make a solid. I should have told you this; I'm sorry that you wasted time on it. Also, on the model to be printed, I have to add material to all the surfaces that will be machined after casting. This model is just to look at.

Here is a picture that will help explain one of my methods. The job here is already finished, so you will have to imagine that the fillet in question is not there, and the red curve is just a rough idea drawn on the surface. Because of the angle, there is no way to project onto this correctly from any of the orthogonal views. So after I've drawn the rough curve, I adjust my viewing angle to that which will work best for the projection. I then draw a line that corresponds to that angle (that's the green line almost hidden among the selected lines). I move that line away from the surface and then I make the plane perpendicular to that line. Next, I copy that line to several points along the rough curve. The lines selected are those lines, which I have extended to fall on the plane. Now I can draw the blue curve between those points. After drawing that curve, I delete the selected lines -- they are no longer necessary. Already, this method washes out a lot of the irregularities of the rough curve, but if necessary, I move the curve's points on the plane until I have a fair curve. Now I can project that curve onto the surface. As I said, even after it is projected, if it doesn't look quite right, I can move the points on the plane again and the projected curve will automatically follow. This is very neat. When I'm happy with the projected curve, I 'Show Points' and move the endpoints to be certain that they are precisely where they need to be. I then use that curve to cut the surface. I'm afraid that this sounds awfully complicated, but when you've done it a hundred times, it goes smoothly. One thing that this method permits is a gap between surfaces that can vary in any way that you choose. It doesn't have to be straight or tapered. It can be narrow at the ends and wide in the middle, or whatever suits the model. I want to mention something else. When you use 'Blend', the bulge factor should be different depending on the angle between the surfaces. But what do you do when that angle changes over the length of the 'fillet'? Simple: At the wide-angle end you will want a bulge factor of maybe 0.8. At the end with the more acute angle, you will want a bulge factor of maybe 1.2. So first, blend the edges at 0.8 and make a cross-section (usually with 'Iso', or just turn the end of the blend into a curve). Delete that blend. Do another with the bulge factor at 1.2. Make a cross-section at the acute end. Delete that blend. If you want to be cute, do another blend at 1.0, and make a cross-section in the middle. Delete that blend. 'Blend' forces you to chop up a fillet wherever there is a single edge. You can now 'Merge' all of the edges that you trimmed to accommodate the 'Blend' tool, and 'join' all the edges so that you then have only two long curves. Select those and all the cross-sections and do 'Network'. Do you get this? You can make fillets that vary in width and vary in bulge-factor and that cover several surfaces! In other words, you have complete control over what you get. Yes, there is some work involved, but there is no way to automate this process and retain this control. And now you see why I say that doing 'fillets' in MOI is a strength, not a weakness.

Here is another model that you can play with.

Hi Tim,

Thanks for explaining!

<<that you wasted time on it

No problem... I just load it --- Join it (no solid) --- ExplodeMove it and render! ;)
All that take 2 minutes! ;)

I will study your last explanation and model...as soon as i have 5 free minutes!

Stranger things indeed! :)

Here is another example. You can see that there are several 'parts' which do not come together in any way. There forms are dictated by their functions. But all these 'parts' have to come together to make one part. As I said, the problem here is nothing like a 'fillet', although the end result often looks like a 'fillet'. This sort of a problem comes up in my work more often than the 'fillet' problem. And when confronted with something like this, the question is: How do I make these 'parts' conform to one another. Let me be perfectly frank and say that I can very seldom see how this should work. So I need a method, like an algorithm that let's me me begin in the dark and slowly come to the light. In this example, I began by making the surface in the center, which goes from a flat plane on top to an ellipse at the bottom. I used 'Blend' to make that -- but first I had to extrude the ellipse at a certain angle that would give me the correct form. With that surface done, as you see here, I went about "drawing" lines on the surfaces of the other parts. The blue lines shown here are not the first or the last that I drew. I draw some lines, and then rotate the view around and look at the whole scene from different angles. My first effort is usually quite poor, but knowing what won't work is information leading to the solution. I keep refining these rough lines until I can 'see' how the connecting surfaces must be. When I finally know what I'm doing, I apply the method that I previously explained, to go from these roughly drawn lines to fair curves that lie on the surfaces. With these I trim the surfaces. Then I use 'Blend' and 'Network' to fill in the gaps. 'Network' is a fantastic tool, but you have to provide enough information for it to work without deformities. 'Blend' is the primary tool that you use to set up the network of curves (the information) that 'Network' needs. When you master this, the results are wonderful.

I gave you a problem which many people might find impossible to resolve. So here is how it turns out.

And natural boolean between volumes don't can give some result ?

Does all that is real pieces or imaginative stuff ?

First, as I said, the "parts" here are dictated by their functions. One of the reasons that I posted this is that a lot of what is done with MOI is aesthetic -- that is, the object is to make something Look a certain way. My work has to be turned into machine parts that have to function, and not just look nice. That object that you did the rendering of is part of a piston, which will see 9,000-rpm in that cylinder. The problems then are quite different. One "part" has to do one thing and the next "part" has to do something else. But these "parts" have to come together into One Part. Without understanding what the engine does, how it operates, you can't appreciate Why every detail of this cylinder must be very nearly as it is. And when I put these "parts" together, I can't compromise their function in order to accommodate the limitations of the software I'm using. And the beauty of MOI is that I don't have to compromise. But there may be other ways of getting the job done. I haven't seen anyone else solving the sorts of problems that I have to solve, so I developed my own techniques. I would be very happy if someone could show me an easier, faster way to do this. But what I've found on the Forum are people getting stuck doing things that I think are trivial. I must point out that in this last example, when I look at the "parts" that I must bring together, there is no one solution to the problem. This is why I have to draw a bunch of lines and keep trying different ideas until I find something that works. And solving this problem doesn't help much when I get to the next configuration -- every arrangement is different and requires a unique solution. But my method always works.

Many thanks for your always very detailed explanations!

PS Can we say that your method is a little like the option "Planar Sections" of the Blend function ?
http://moi3d.com/forum/index.php?webtag=MOI&msg=6790.35

I haven't used the Planar Sections option -- but I thank you for suggesting it! There are still some complex geometries that take a lot of time to get right. The Planar Sections option might help in such cases. The main technique that I wanted to offer is that where I can draw rough curves on a surface in order to 'see' what I want to do next. Then, use Project -- from an appropriate plane -- to get a fair curve that is actually on the surface. That curve is adjusted and used to trim the surface. All this must be done Before using 'Blend', as you have to have corresponding edges to work with. I also want people to understand that the limitations of 'Blend' and 'Network' can be largely overcome by using both of them together. There are several other tricks that I use but did not mention. 'Network' has a tendency to curl the surface as it approaches an edge. To fix that, I usually use 'Iso' to give me some curves that lie on the not-quite-right surface. I often 'Rebuild' these curves, reducing the number of points, which washes out a lot of minor distortions. Then, I adjust the points on these curves, near the curled edge, so that they are tangent to the surface. The trouble with 'Network' is that it doesn't take into account the form of adjacent surfaces, so we have to provide enough information so that those intersections will be tangent; and this is what I'm talking about. When I have those new curves corrected, I run 'Network' again and the curl at the edge is gone. I didn't mention a problem with 'Blend'. You have to break up a 'fillet' at every intersection, as you cannot add edges (as you can with 'Network'). And when the geometry is complicated, those short sections of Blended 'fillets' don't fit together well. They may look okay from a distance, but it you zoom in, you will find that there is a gap or the edges overlap. But if you use those Blends only to give you cross-sections (which are properly tangent to the adjacent surfaces), then delete those Blends and run 'Network', everything fits without errors.

Thanks for these extra infos!

Just a little thing ;)
The position of the click of the Blend function gives not the same result!
That was the same for the surfaces in the past but as that was some perturbating i believe that Michael stop it!

Only subsists that for the curves! ;)



PS Of course i have forgotten the normal way ;)

You asked about 'Joining' the surfaces of the cylinder model. As I said, the model shown was just to look at. One thing that I did in that regard was to make curves of all the edges that I want to be seen as edges; then I gave them a different color. This looks much better than otherwise. Of course you want to hide all the edges of surfaces that should look continuous. But when you hide the edges, the edges that should look like edges become sort of fuzzy. To change the model for 3D printing, I eliminated all those curves, so that I had only surfaces. I also eliminated all the 'holes' (screw holes) which were open on the bottom. I then 'Joined' the surfaces. Only one had a problem! Think about that: More than 1400 surfaces in this model and only one problem. That surface was a simple one and I redid it in a few seconds. Then the whole cylinder was one joined-object. Let me say again that my method is to 'Project' a line onto a surface. Then, I move the endpoints of that line to the intersections of the surface. This eliminates a thousand errors that prevent the edge of one surface from matching the edge of the next surface. Only then do I use this line to 'Trim' the surface. Also, as I said, 'Blend' will frequently mismatch the edges of fillets, where more than one 'Blend' is required. Using 'Blend' to make cross-sections, and then using 'Network' to build the fillet eliminates those errors. When I started with MOI, I was doing what I thought should work, but when I zoomed in, I found too many mismatched endpoints. How could I avoid these? I found that the best way was always to begin with a line, adjust the endpoints, then 'Trim'. This is how I produce more than 1400 surfaces without errors.

Another cool explanation!

<< 'Project' a line onto a surface. Then, I move the endpoints of that line to the intersections of the surface.

a projection don't put the extremities of a curve at the intersection of the surface ?


else ...
What will your strategy for this little case where fillet don't work ?

http://moiscript.weebly.com/uploads/3/9/3/8/3938813/fil_dont.3dm

__As to your first question. In many cases, you might not project a curve, but instead, in one of the orthographic views, cut the surface directly. This saves a step, so why bother to project the curve and move the endpoints? Well, I started out doing it that way, and I found that too often I ended up with spurious endpoints; that is two or more "endpoints" very close together. Which one is the "right" one? In some cases, I ended up with three or four "endpoints". This led to all sorts of problems, so I had to find a way to work so that I only had one true endpoint or intersection. I can't tell you why we get these errors. In theory, the points should work out right, but in practice these errors keep coming. I call them "rounding-off errors". In any case, when I project lines and adjust the endpoints, I eliminate the errors.
__As to your fillet problem, this was simple. First, I copied the cylinder where you had projected the curve and cut the hole. Then I copied the other part and aligned them. I then made the blue curves and did a 'Blend' between them. This is using 'Blend' with curves only, not surfaces. I then projected the red curves onto both objects and did another 'Blend' between them. Now I could use 'Network' with three true cross-sections between the two objects. It's the same, top and bottom. You can see the result with the edges hidden. It's not quite perfect. One more step would project two more lines and due two more blends to get two more cross-sections, between the ones that I did the first time. You have to give 'Network' enough information to work with. In this case, only one cross-section between the ends of the fillet is not quite good enough. Obviously, if I wanted to I could add as many more cross-sections as I thought necessary, but you can see that only one (between the ends) looks good and you have to look closely to see that between those sections 'Network' has exercised a bit too much "imagination".

Many thanks!

I believe that I have quasi all understood this time!
And sure blend the lateral blue curves gives a better result than my manual drawing!

Maybe a method can increase the speed process
Add cut point(s) on the "edge(s)" (not the curves) for have 2 parts or more for make Blending surfaces (in easy cases) or Network!
That avoid to cut volumes!
All surfaces in this follow easy case will make a "solid" even with the "Blending surfaces" !

__What I've tried to convey here is the use of 'Project', 'Blend', and 'Network'; which together can solve almost any problem. There are other tools that are useful, and in many simple cases another method may be quicker. But when you have a problem that you cannot solve using your own methods, this technique will work. I've been using this on thousands of cases of every configuration and I always get the result that I want. But what can't be taught is how to use this method to solve a Specific problem. These are of infinite variety and only experience will help a person see how to proceed. Too often, I go about something in the wrong way, with a poor result. But when I know what Not To Do, I am a big step closer to seeing the right approach. In the problem that you gave me, you tried a few things that didn't give you what you want. I looked at it and immediately saw how I could blend a couple of lines that would serve as cross-sections for 'Network', and gives a good result. That's what can't be taught; that's all about experience. But I'm still learning!
__I'll give you one more tip. When using 'Network', 'Normal' sometimes gives a lumpy surface. 'Lighter' smooths it out. (I guess that's why it's there!) BUT, 'Lighter' often pulls the edges away, so that the edge of one surface doesn't fit the edge of an adjoining surface -- even though the endpoints are good. This is exactly the sort of condition that you want to avoid, so it is best to use 'Normal'. In cases where 'Normal' gives a lumpy surface, there are two ways to fix it. First, use 'Iso' to map a grid onto the 'Normal' surface. 'Show Points' on the grid, and you will see that there are too many points -- which are necessary to define all the little bumps and hollows. So, with the whole grid selected, 'Rebuild' the curves, going from maybe 30 points to 6 or 8. Then delete the surface and run 'Network' again. In this way you have eliminated a lot of information that was responsible for the surface irregularities. In really bad cases, you can do this process more than once, each time washing out irregularities and smoothing the surface. The second method is to use 'Lighter'. Then Iso a grid onto that surface. Delete the surface. Now, one by one, move each endpoint of the grid 'On' to the corresponding edges (which corrects the errors that 'Lighter' introduces). Then run 'Network' again in 'Normal' mode and you will get the cleaner surface of 'Lighter' without the edges pulling away.
__And here is something that you may not have tried. Say that we have a four-sided hole to fill between four other surfaces. ('Network' only works with three or four sides -- so if you have five sides, you have to subdivide the area before you can use network.) Now, let's say that you have a grid of four curves. These intermediate sections do not have to stop at the edges of the adjoining surfaces! They can continue onto those surfaces and thereby insure that the new surface will be tangent to the existing surfaces. It appears that 'Network' calculates the surface form differently if these intermediate curves stop at the edges or continue beyond the edges. Try it both ways and see how it works. As to how you get those intermediate curves to fit the adjacent surfaces and pass over the empty space of the hole that you want to fill, here is where 'Blend' comes in again. You can trim edges into short sections, and use 'Blend' between those sections. Change one edge of this narrow blend into a curve, then delete the narrow surface and you have a cross-section that is tangent to the surfaces. Remember that you can vary the 'Bulge' factor from one cross-section to another, which gives you great control over the form of the surface (but can also give a wavy surface if you have different bulges too close together or radical differences in bulge factors that don't fit well with the existing surface edges!). The amazing thing is that, even when you define an irregular form, 'Network' will produce it. This is the price paid for creative options: You can do bad as well as good!

Another cool advices!