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BLSmith

Loft Parents & Spline Children: Priority

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Hi all. Lets say I have 3 splines in the shape of a rectangle, each spline smaller than the last. Now lets say I put those three splines under a Loft object. As I move one of the splines along the Z-axis, a border is now visible around the other two splines, however, if I change the hierarchy of those three spline objects in the object manager, moving that same spline produces a different look. Can anyone explain how a series of splines under a Loft works? I've never modeled anything before and am taking baby steps. Thanks! 

 

Video version of the above question (2 minutes): 

 

Thanks!

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Loft is parametric object, so for removing "cap" you need disable cap options in Cap tab of loft object.

Splines are calculated from first to last in loft  object hierarchy

 

https://www.dropbox.com/s/0btx03w4ym6e20q/Loft.png?dl=0

 

Splines are only "frame" for creating "surface". For best results are important few things, poincount and alligning splines. With alligning splines is meant spline points "direction".

(spline point 0 of first spline will be connected to spline point 0 of second spline etc. and in case your splines has opposite points direction, surface result will not be correct.)

 

Mesh subdv in both directions could set/improve mesh result to your needs (rough/smooth etc). 

 

 

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Yes, Lofts have a very specific workflow associated with getting the best results out of them.

 

As Bezo says, the order of splines is most important, and the direction of those splines must be the same (this is shown by the white (start) to blue-ness (end) of the spline). Additionally, there is a weird anomaly about the Loft Object to do with segmentation, which is not controlled by the splines in a Loft Object. But if you want 16 segments around your loft, you have to set 17 (target number+1) in the attributes. This is the ONLY generator to which this rule applies !

 

The caps options in lofts cannot produce neat topology, so I find it best to just turn those off, then add my own nicely modelled caps when the Loft is later made editable. Or you can leave them on but set to ngons, which allows you to cut them up into quads later.

 

As far as to what segmentation you should choose, it depends if you are going to use SDS or not, but presuming you are you only need the minimum possible amount of polys in both directions to hold the curvature, and you can rely on SDS to do all the smoothing for you. You should aim to get as near as you can to perfect squares, which later subdivision will thank you for.

 

Lofts are among the most useful of the generators if you use them with these things in mind...

 

CBR

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  • To Bezo:

    Quote

    spline point 0 of first spline will be connected to spline point 0 of second spline etc. and in case your splines has opposite points direction, surface result will not be correct

    So if I understand correctly, lets draw a spline, each point can be given a number (say 1-8), and then we draw another spline with another 8 points, the loft object will draw geometry between each corresponding points (as illustrated by the yellow boxes below on these two splines). 

     

    image.thumb.png.36f75435d29f1905407cab6295b2fde9.png

     

    To Cerbera:

    Quote

    But if you want 16 segments around your loft, you have to set 17 (target number+1) in the attributes. This is the ONLY generator to which this rule applies !

    Interesting!

    image.thumb.png.ecfaa7f79297fcd28b15531c3ceef8b0.png

    I see what you mean about caps being messy. 

     image.thumb.png.1dca4b914b8cd3b97a50642431e5ce9b.png

     

    Thanks guys for the comments. It's a bit difficult still to wrap my head around priorities but I suppose knowing the rules is half the battle and I can guess change the order a few times and eventually I'll get the order right. 

     

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    Caps are messy, but more so here than usual, because you are using that Loft for something a loft shouldn't be doing. It is the wrong choice of generator if you are going to have all your splines at the same Z position !

     

    Use of the loft would make sense if the splines were spread along Z, and you were trying to make a long tubey thing from your circle profiles, like say an Airplane's fuselage, but if your splines are concentric circles the loft has nothing to do that can't be done better just using a poly disc primitive ! By using it in a way that doesn't suit the tool you are setting yourself up for endless intersection and overlapping geo, and it will be very hard to keep track of which spline is where.

     

    I made you a little video about this, which I whazzed over to your email.

     

    CBR

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  • Sorry for the delay! Works been crazy. 

     

    Thanks so much for the video Cerbera! Learned a ton, your like the Gordon Ramsy of modeling. To boil it down, I think of it like Knex where each piece connects to the next and the order of each joint creates the shape we ultimately see, if the pieces are out of order all heck can break loose. 

     

    image.thumb.png.ca110d09fa375c3adada54fc7bf78971.png

     

    To create the caps, as we talked about in the previous step, while a "triangle," cap type would work, it would be super ugly. To fix this, one could change the Loft cap type to "n-gons," but if it's ever a child of a Subdivision Surface (SDS), it will ultimately look just as ugly as it did when it was set to "triangles". A good method to fix this, is simply not to have Loft caps, but address it in an additional step.

     

    To generate a new cap: Select all the splines, set the shape as editable > enter edges mode > right click and choose "close polygon hole," select the cap edges and click. By default, the new caps are not split into quads and IRRC @Cerbera is a big fan of making sure each piece of the model is split into quads. Using the knife tool, each cap should have 4 sides rather than being a flat piece. Whats more, there should be better edge flow (a term I need to learn). To create a better edge flow, with the live selection tool active while in polygon mode, select the new cap quadrants > right click and choose "bevel inner," while click dragging to create more definition on the caps. 

     

    image.thumb.png.f198de4dd44b0964790d5fc4dc6018ff.png

     

    Two questions:

    1. What is the difference in setting the "Mesh Subdivision," inside the object tab of a loft vs. having that mesh setting be as low as possible (9) so that an SDS can take control of it? 
    2. What makes a good cap? So in the image above, the left example is "bad," because it is a large piece connected by 8 sides, and I suspect that's bad because it should be 4. So we create 4 more polygons by slicing it down the middle, now each quadrant connects to 4 lines (I suck at the verbiage), but what prompts creating an inner bevel? 

    Thanks! :)

     

     

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    1 hour ago, BLSmith said:

    What is the difference in setting the "Mesh Subdivision," inside the object tab of a loft vs. having that mesh setting be as low as possible (9) so that an SDS can take control of it? 

    The difference lies in how easy it is to cut the ends up into quads. By using the minimum segments necessary in the loft we assure ourselves that will be easy as it can be, and also retain ultimate polygonal efficiency - ie more of the subdivision is calculated at render time and isn't baked into the file adding to its size...

     

    But shouldn't let that alone decide what segmentation is done where. We should think about what additional details might need to be modelled into this later and  let that principally decide what we keep in our base mesh. In this case I am assuming zero additional detail, so the minimum of 8 is fine.

     

    1 hour ago, BLSmith said:

    What makes a good cap? So in the image above, the left example is "bad," because it is a large piece connected by 8 sides, and I suspect that's bad because it should be 4. So we create 4 more polygons by slicing it down the middle, now each quadrant connects to 4 lines (I suck at the verbiage), but what prompts creating an inner bevel? 

    Yes, the first one is bad because it is a ngon, which SDS will subdivide seemingly at random, and almost never the correct way. It's edge flow is anyone's guess.

    The second one is better because at least we have now all quads, which is what SDS wants. But its edge flow is still going across the object in 2 directions.

    We can change  / redirect the edge flow AROUND the object by doing the 3rd pic with the Inner extrude, so now the edge flow is circular on the outside, and therefore neatly isolated from the topology down the object. It also gives us a control loop on both sides of the rim, which will give a considerably more evenly tight ending than 1 alone.

     

    1587385475_edgeflowend.png.ef3e56002df1a0c32a4a043f44fae88b.png

     

    That makes sense ?

     

    Have a look at the edges going round the object as it goes down the length - that is still too many segments there. Aim for squares if you can, which is what SDS works best of all with...

     

    CBR

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  • Ohh I see, I think. So this is my understanding:

    1. So with the loft still active, we can't create a cap because because it is not an editable object. We make the loft object editable in its easiest form to divide, in this case 9 subdivisions  (but really 8) segments, which can be easily eyeballed with the knife tool to make into 4 slices, and we get that quality control back once we apply a subdivision surface. 
    2. By converting the loft object hierarchy to an editable polygon to it's simpliest form, we also make our file size smaller, and the subdivision surface is really only adding complexity (my poor choice of words) during render time. 
    3. Subdivison surfaces wants only quads when subdividing.
    4. By having the inner bevel (image 3), we allow for a border of sorts around the edges so they aren't going in two different directions (image 2) which is better. I'm a little unsure the reasons for this. 

    I think I need to do more work on understanding basic concepts such as what edge flow is. After a quick google brought me right back to C4D Cafe, I'm considering starting this youtube playlist if it's still useful in C4D 7 years later: 

     

     

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    Ohh I see, I think. So this is my understanding:

    1. So with the loft still active, we can't create a cap because because it is not an editable object. We make the loft object editable in its easiest form to divide, in this case 9 subdivisions  (but really 8) segments, which can be easily eyeballed with the knife tool to make into 4 slices, and we get that quality control back once we apply a subdivision surface. 

    Yes.

    1. By converting the loft object hierarchy to an editable polygon to it's simplest form, we also make our file size smaller, and the subdivision surface is really only adding complexity (my poor choice of words) during render time. 

    Ordinarily yes, but actually no with a Loft, because if that is still parametric, then there are no polys at all being stored, just splines, which are lighter than polys in file size at least...

    1. Subdivison surfaces wants only quads when subdividing.

    Yes, but that is not to say it won't deal with tris or ngons, just that you will have no control over HOW it deals with them, so best to avoid altogether.

    1. By having the inner bevel (image 3), we allow for a border of sorts around the edges so they aren't going in two different directions (image 2) which is better. I'm a little unsure the reasons for this. 

    The reasons for this are manifold and complicated and would take more time to explain than I have right now.

     

    I think I need to do more work on understanding basic concepts such as what edge flow is. After a quick google brought me right back to C4D Cafe, I'm considering starting this youtube playlist if it's still useful in C4D 7 years later: 

     

    It is still useful, if you keep in mind that all the knife tools are different now, Hypernurbs is the legacy name for what is now an SDS object, and some shortcuts are different too in later versions. It won't tell you everything, and not much in the way of reasons why we do stuff, but it will show you a good overview of the basics. Also check out the modelling tutorials on the cafes own Youtube channel where the tools are more up to date, and we can't get a better teacher than our very own @Hrvoje...

     

    CBR

     

     

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  • 1 hour ago, Cerbera said:

    Also check out the modelling tutorials on the cafes own Youtube channel where the tools are more up to date, and we can't get a better teacher than our very own @Hrvoje...

      

     CBR

    I think I'll start there with something I can follow in terms of its relevance to current C4D indeed. Thanks Cerbera! Definitely know a lot more now than when I started the thread :)

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