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Why am I getting these artifacts at the arcs of my geometry?


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Not enough information provided to know for sure. We can guess it'll either be to do with material mapping modes or a phong issue, or because of the horrible geometry created by splines and generators with duff settings. You should provide the scene file with questions like these, and complete your profile so we know which version of the software this is.

 

CBR

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You are getting a result like that because of 2 factors:

 

1. The Boolean has created typically horrendous geometry, full of triangles and wildly divergent poly sizes.

2. You are trying to use the UV mapping mode for the material, which requires clean even polys to work nicely with displacement.

 

These 2 non-optimal things are conspiring against you here and because you appear to be using displacement in the material, which will fail with such ropey geometry ! Displacement REQUIRES even (ideally quad) geo to look correct in render.

 

image.png.9713c1e94535ce67c17d64c1aa4a0031.png

 

So, a couple of solutions to choose from:

 

1. Rebuild the object more correctly, out of polygons, to achieve nice even, regular quad geometry. Slowest method but also best results and no horrible booles involved.

2. Use the current object, but don't use displacement - use bump or Normal Maps instead, which don't interact with the duff topology in the same way.

 

Just to let you know, Boolean operations are there as quick, lazy, desperate alternative for people who a) can't yet model properly, b)are massively short on time, or c) for the very few and specific circumstances where they can be used correctly in a professional workflow to achieve a certain result or animation. To use them as the first recourse in any modelling task is a mistake a lot of people make early on - they are prone to error in all sorts of ways, and notoriously flaky and unreliable when pushed beyond their somewhat limited abilities. I really would advise learning to poly model asap so that you can avoid these sort of issues.

 

CBR

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Thank you @Cerberafor the detailed reply. How do you display the mesh wires like that? I tried to turn that on but I was not able to.

 

I think the problem is not he boolean but the Spline Mask.... C4D letting me down every step of the way 😞

Is it pretty unavoidable to use boolean when creating an archway hole in a wall...

 

I found this tut, but he does not really make a perfect circle for the arch, which I would like to.

 

 

I actually tried making the boolean again, but this time with a Sliced Cylinder and a Prism. As long as you delete the duplicate face (top of prism and bottom of cylinder) the Bool works flawlessly. Too bad there is no command to delete inner faces... I tried mesh optimizer but does not solve it. Too much work for a simple arch it seems.

 

image.png.188805f81008ac0263c18094eb01423c.png

 

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5 minutes ago, ShynnSup said:

Is it pretty unavoidable to use boolean when creating an archway hole in a wall...

Au contraire my friend 🙂 It is entirely possible to create beautiful archways in walls with no booles, splines, generators, or spline masks at all ! it takes a little longer than the cheat-y ways, but produces a much more robust and polygonally correct result. I will show you one of those if I get time later today...

 

CBR

 

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I get my screen like that largely by having R25, but also have changed my background and shaded wire colours in preferences / schemes / editor colors etc...

 

Here are 3 approaches for arches, none of which involve splines or booles. All render perfectly.

 

In the leftmost one I am building a Hard Surface model, with minimal polys, but every one of those polys is a quad, and each edge is exactly where I want it because I have made it from polygons from the ground up. This still won't work with displacement textures because the polys are not yet even enough but it does serve to show how you can make a beautifully rendering, nicely bevelled, correctly modelled arch without splines or booles.

 

In the middle 1 I have added enough edge loops to the HS model from earlier to make it suitable for displacement textures - note how regular and even the polys are across the whole mesh...

 

In the 3rd example we have a Subdivision Surface Mesh (SDS), which allows us to get resolution-less curves with really very few polys, which also gets us a perfectly acceptable rendered result, and one suitable for displacement textures...

 

1657168818_ArchesCBR.thumb.gif.4265c35c948cd0def3cc5d7637a0f249.gif

 

So all these things are options and all of them arguably better and more robust and controllable than any of the spline methods you went with before.

 

In the HS examples above I started with this simple sliced disc primitive, and in the SDS one, the same, but with much less segmentation, as SDS will be handling the curvature.

 

image.png.75e605930b138b4340ad26efe85659ce.png

 

Here's a file with all that in so you can have a proper look round...

 

Arches CBR HS vs SDS.c4d

 

Hope that helps ! 🙂

 

CBR

Edited by Cerbera
Added info pls refresh page (see edit history)
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Uff, thank you CBR!

 

So to clarify, starting from the disc primitive, you then moved the two bottom edges to make the legs, and then extrude in Z to add depth? What I don't get is how did you add the X thickness, which transitions from an arc onto a rectangle. If you could clarify this for me because despite your detailed reply I have no idea how to get from a disc to an archway.

 

btw I still can't get those mysterious edges to display.. (using S24)

 

image.png.922051c0f58e4da416440b517d560e9b.png

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Ah you mean the triangle lines in your original mesh ? Well I made the boole editable to be able to see those, but you can do it without that stage by disabling hide new edges in the boole options.

 

Yes I extruded the 2 ends of the arch down to get the length, but didn't add thickness until I had expanded the wall section to have straight edges. That I did by selecting groups of edges, ctrl-dragging them out and zero scaling them straight, like so...

 

445728084_Arches2CBR.gif.c1510c2153c1b4bb0d6533e02dc5434e.gif

 

In each case I am selecting a group of edges, ctrl-moving them out to extrude, then zero scaling (holding shift to quantize to exactly 0)

After that you can use Edge Cut or Loop Cut to make additional edge loops as needed, then add thickness in poly mode by selecting all and doing Extrude Tool (with caps)...

 

CBR

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An alternative workflow exists, but it is not directly possible in Cinema4d. A boolean workflow for hard surfaces like these is possible with a good remesher. The problem is, as always, time and effort. Suppose you or the client must iterate quickly through various versions, and time/cost is also a factor.

 

A remeshed version may not result in great geometry, but it will render fine, and allow for quick turn-arounds.


Cinema4D also features a remesher generator, but it is unusable for these type of hard surfaces. Blender's remesher, however, works quite nicely, and includes options to harden the normals to avoid rendering artefacting.

 

That said, you could export your boolean'ed objects to Blender, remesh, and reimport in Cinema4D for rendering.

 

Here is an example: I've used Blender's remesher modifier to convert the boolean mesh messy geometry to one that uses quads only, and it is even possible to bevel the edges afterwards.

By controlling the remesh parameters it is possible to come up with quite acceptable results and it will render fine.

 

The advantages are quick renderable hard-surface models which can be tweaked quickly and adjusted to various resolutions. It is a non-destructive workflow, and allows the user to use booleans and create new variations effectively without having to worry about geometry. It renders fine.

Modeling perfect/great polygonal geometry requires more experience, more time, and is in essence a destructive workflow and difficult to adjust later for even small changes. It requires more planning and does stunt the creative flow somewhat - which is why many artists will quickly block out stuff early in the process, and later create an optimized poly flow.

 

The disadvantages: obviously it generates a heavier less optimized mesh. And less control over the final low resolution mesh. UV mapping may take longer and involves many more faces to deal with, of course. If this is supposed to be an highly optimized model for game dev work it may not be suitable depending on the requirements.

 

PS another approach would be to use retopology tools to manually create a new optimized mesh based on the boolean version. Takes more time, though, but it allows for full creative freedom during the design process.

 

exampleremesh.jpg.4cd4354eef462bbb1f55c0e95113efad.jpg

 

settings.jpg.c27c89e813a7c2d0a875fa3db633ef40.jpg

 

 

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