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Help me model this robot. Problem with extrusions on curved surface.


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Hi all,

 

New here, seems like a great ressource.

 

I'm new to C4D, and trying to model this robot as a challenge.

 

Robot.thumb.png.95fcded301dddc93b6de56656f2bf1b1.png

 

I've been following this tutorial, explaining how to do a "180° cut" to have clean edges and angles on curved surface extrusions. My problem is that the outer corners of my extrusions are still not that clean.  After A LOT of tweaking, I still have some minor but visible artefacts / shadows around the corners.

 

1/ Can someone take a look and tell me what they think about my geometry (I attached my file and some screenshots) ? Am I being too concerned over small details ?

 

2/ Can someone criticize my process ?

 

- I started from half an hexahodron sphere. And worked in symmetry.

 

- For the "middle eye", I selected the edges of the polygons I wanted to extrude down and straightened them one by one using the scale tool. Then I inner extruded the area. Extruded it down. Shaped it using the move tool for the bottom part. Set up my 180 cut all around. Beveled or used control cuts on the edges I wanted to sharpen.

 

- For the "side eyes", I selected the area, inner extruded it. Extruded it down. Used the slide tool to shape it the right way (gave up on the bottom corners). Set up my 180 cut. Beveled or used control cuts on the edges I wanted to sharpen.

 

- For the "horns" on the head I was planning on using another object. Maybe by splitting off part of the sphere.

 

- For the body I was planning on starting from a cylinder. And extruding to create the arms and other details.

 

Thank you in advance for your help,

 

Screenshot 2020-07-21 at 20.44.08.png

Screenshot 2020-07-21 at 20.44.18.png

robot_test.c4d

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  • I would have started with the inner sphere, and extruded out from that, which would have been less work overall.
  • The reason you still have shading errors is that you are allowing complex poles under subdivision, and because of a large discrepancy between largest and smallest polygons in proximity to each other, the prevalence in places of contra flow edge angles, none of which Sub-D likes.
  • The 180 degree cut is fine in some circumstances but not like here where there are sharp areas very close together on curves.
  • For this it is perhaps preferable to use staged subdivision instead which involves primarily establishing your curvature to a much higher level of polygon density before you do any extruding.
  • The spherify deformer would be a great help in modelling this at various stages...
  • Symmetry would also help and halve your workload in places.

Am in a recording session at the moment, so can't explain in any more detail than that for now, but may pop back later to expand on it if I get time, and no 1 else beats me to it...

 

But if you would like a custom skype session with me (would need 2 hours minimum) to explain the complete workflow and strategies applicable to this, I do offer that as a service - pls PM me for details if that interests you.

 

CBR

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2 hours ago, Cerbera said:

But if you would like a custom skype session with me (would need 2 hours minimum) to explain the complete workflow and strategies applicable to this, I do offer that as a service - pls PM me for details if that interests you.

 

CBR

Whooa....really?

 

Uxos - IMHO, there is no one better at hard surface modeling than Cerbera.  That is quite the offer!!!  His community reputation score is purely based on his work and the problems he solves for others.

 

Dave

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3 minutes ago, 3D-Pangel said:

Whooa....really? That is quite the offer!!!  

Yeah, those are paid things unfortunately, in case you are misunderstanding 😉

 

Happy to help as much as I can on the cafe in threads like these and via GIFs and videos and whatnot, but personalised Skype jobbies take another level of prep and explanation time so alas can't be free...

 

Thank you for the kind words though 🙂

 

CBR

 

 

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Just now, Cerbera said:

Yeah, those are paid things unfortunately, in case you are misunderstanding 😉

 

Happy to help as much as I can on the cafe in threads like these and via GIFs and videos and whatnot, but personalised Skype jobbies take a lot of prep and explanation time so alas can't be free...

 

Thank you for the kind words though 🙂

 

CBR

 

 

I certainly expected that there would be a charge for this service.  I would have been more surprised if it was free.  I was just amazed that it was something you would offer as it would be something that you would put a lot of prep into (for some reason, I am guessing that you are a perfectionist who likes to do things right...and do it right the first time.  That opinion probably comes from those perfect quad meshes you create).

 

One thing I would like to strongly encourage you to consider:  A tutorial on solving tough and/or common modeling problems in Cinema 4D.   Essentially the techniques for making only quads in various modeling situations - especially those involving curved surfaces and/or intersecting curved surfaces .  The course would NOT be for the beginner as it would require familiarity with C4D's modeling toolset and short cuts - but rather just the techniques that you have developed.  Focusing on the techniques only as opposed to teaching basic tools would be enough work  as I would imagine that coming up with appropriate examples and structuring the lesson to clearly explain the solution would be challenging.

 

I would pay dearly for that type of training.

 

Just a thought....and a hope.

 

Dave

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Thanks Cerbera for the detailed answer. I reflected on your comment, and did a few searches based on your suggestions. I now have a way better understanding of the problem at hand.

 

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I would have started with the inner sphere, and extruded out from that, which would have been less work overall.

 

That's clever indeed. I will try starting once again using this technique.

 

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The reason you still have shading errors is that you are allowing complex poles under subdivision, and because of a large discrepancy between largest and smallest polygons in proximity to each other, the prevalence in places of contra flow edge angles, none of which Sub-D likes.

For this it is perhaps preferable to use staged subdivision instead which involves primarily establishing your curvature to a much higher level of polygon density before you do any extruding.

 

So poles = shadows. And too different polygons sizes = troubles. The two of which can be solved by a higher mesh density, if I get what you mean. I knew it had something to do with some of the long edges I got in the bottom of my object and I see how they would not exist if I had more polygons.

 

So if I understand correctly : I should create my sphere as I did, make it editable. Then subdivide it. Make my sub-d editable and tweak my mesh so my geometry is closer to the shapes I want to achieve. While being careful to keep my polygons as even sized as possible. Only then should I start my extruding. I can then sharpen my corners by using some of my existing polygon edges as control edges by sliding them with the slide tool.

 

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The spherify deformer would be a great help in modelling this at various stages...

 

Never tried it, but I just watched a video, and indeed, I think I can guess a few ways it could be of use. I need to dig a bit on the matter, I will try searching the cafe and youtube for answers.

 

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But if you would like a custom skype session with me (would need 2 hours minimum) to explain the complete workflow and strategies applicable to this, I do offer that as a service - pls PM me for details if that interests you.

 

Tempting but I'm broke at the moment with the pandemic and all, plus I'm not the best english speaker IRL. But I appreciate the offer and will consider it in the future if I can. You've already been of great help, thank you.

 

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so alas can't be free

 

And that is perfectly normal. Everyone got to eat !

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4 hours ago, uxos said:

So poles = shadows.

Nope, or at least only if they are really bad. More commonly the primary symptom is unpleasant SDS pinching and bulging.

 

4 hours ago, uxos said:

The two of which can be solved by a higher mesh density, if I get what you mean. I knew it had something to do with some of the long edges I got in the bottom of my object and I see how they would not exist if I had more polygons.

Yep - succinctly put. The staged subD way keeps polygon density almost uniform all the way over the model, so subD loves it and works with you rather you having to fight it, which is what happens when there are not enough polys to do the job nicely...

 

4 hours ago, uxos said:

So if I understand correctly : I should create my sphere as I did, make it editable. Then subdivide it. Make my sub-d editable and tweak my mesh so my geometry is closer to the shapes I want to achieve.

The key stage here is to make your base topology at low level, ideally using SDS weighting instead of control loops to get sharpness, then apply a level or 2 of subdivision (make the SDS editable) spherify the result so you regain your perfect roundness but now with the edge flow you need, lose the weighting then you have established enough curvature to extrude sections... that goes under another SDS, but this time only level 1 or 2 max, and at this point you can deploy some symmetry, and slide points about on the surface to refine shapes, and any controls you do need to add will have extremely minimal effect on the SDS because the discrepancy between those and the general polysize will be so small.

 

Will be back tomorrow to answer a few more specific points...

 

CBR

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On 7/22/2020 at 4:40 AM, Cerbera said:

The key stage here is to make your base topology at low level, ideally using SDS weighting instead of control loops to get sharpness, then apply a level or 2 of subdivision (make the SDS editable) spherify the result so you regain your perfect roundness but now with the edge flow you need, lose the weighting then you have established enough curvature to extrude sections... that goes under another SDS, but this time only level 1 or 2 max, and at this point you can deploy some symmetry, and slide points about on the surface to refine shapes, and any controls you do need to add will have extremely minimal effect on the SDS because the discrepancy between those and the general polysize will be so small.

 

So I wanted to update you on my progress. After many atempts, I managed to get my corners somewhat looking like I wanted using the stage SDS technique you explained.

 

I didn't use weighting, since I didn't understand how to use it in this case, I just slid my points at low level, and tweak them a bit less each time I added a new sub-d level.

 

Thanks again, I still need practice to make it perfect but I learned a lot ! Cheers

Screenshot 2020-07-25 at 23.06.36.png

Screenshot 2020-07-25 at 23.07.00.png

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