Advice for rendering sheer stockings in 3DL

Comments

• Singular Blues Posts: 737

  September 2017

  Geometry is 2D. That seems a weird idea, because the is 3D, but it is, in fact, 2D.
  
  Imagine for a moment, a sheet of paper. It has length, width but is lacking in depth (Yes, I know that's not strictly tue, but it is thin enough to cut, so it will do for this example). Pick up that sheet of paper and roll into a tube. Now it is 3D cylinder made froma 2D plane. Geometry is like that. A bunch of 2D planes tiled together to form a 3D shape, but each plane is not notionally 2D like the paper example. It really has no depth.
  
  You can make a geometry, like a primitive sphere or cube that, taken as a whole has a real volume, but it still made of planes of thickness zero.
  
  There's a point to this.
  
  Because the stockings have no thickness, if they actually touched the surface of the leg, they would basically be occupying the same space as the leg, and you wouldn't see them, at all, or you would see "poke through" as the render engine somewhat randomly decided that this pixel is leg and this one is stocking. So clothing, in general floats a bit above the surface of the underlying model. With sheer clothing, this results in some angles where you look through the stocking, through the gap between the stocking and the leg, and see the back of the stocking again. This the dark line. That line is the gap between geometries.
  
  Now, if you change the lighting method, or render logic, you get points where the engine is, again trying to sort of work out, is the pixel this or is that. In the case of your second problem, my guess is that the gap is too small, and the engine can decide if it is transparent and there is something to see, or if the underlying area is fully shadowed. I could be wrong, there, and it could be another type of aritifact, but it definitly is being cause by the interaction between those two sets of planes.
  
  I haven't found any good solution to this with any render engine. If I had, I would definitely sell it.
• Richard Haseltine Posts: 108,060

  September 2017

  Try lowering the Shadow Bias setting on the light(s) - it's an offset, used toa void the mesh generating shadows on itself (which show up as dark bands) but here soema reas of the stocking are closer to the skin than the offset value (and so don't prodce shadows) while others are more distant (and so do shadow).
• mmalbert Posts: 412

  September 2017

  Thanks for the explanation Singular Blues; that makes things much clearer.

  I'll try a few more test renders and play around with the Shadow Bias settings. I did turn shadows off on the stockings,thinking this was what was causing the problem, but depending on what lights I used the results were hit or miss.

  Aside of simply fixing the blotchy stuff in postwork, I'll see if I can get better results using an overlay in the leg area or just making a second skin for the leg textures with this project. 

  Again, thanks for the help!
• Singular Blues Posts: 737

  September 2017

  No problem. I should add, a little bit of offset is good for creating the illusion the stockings have a thickness, but it's really hard for Studio to get the collision just right. Textures are good way to get around it, for most cases. Maybe not so much for closeups, tho.
• JOdel Posts: 6,316

  September 2017 edited September 2017

  If you aren't showing the edges and toe caps, or need seams, you can just use shaders. I can't remember which packages have stocking textures, but there are some, even though most of them are for Iray. 

  In a pinch you can select the legs and feet in the surface tab, apply a bump from some stockings that you already have and adjust color to match.

  It's a bit of a mess to undo, but you can just save that particular copy in case you ever need to use it again. Doesn't work for lo-cut shoes where you'd be seeing the toe caps, but that example you've got would probably work.

  ETA: unless you want the wrinkles around the knees and ankles. Those need actual stockings.

  Post edited by JOdel on September 2017
• Gator Posts: 1,319

  September 2017

  Richard Haseltine said:

  Try lowering the Shadow Bias setting on the light(s) - it's an offset, used toa void the mesh generating shadows on itself (which show up as dark bands) but here soema reas of the stocking are closer to the skin than the offset value (and so don't prodce shadows) while others are more distant (and so do shadow).

  Richard, I noticed dark bands with Iray, when I assume there is either poke through or the objects are too close.

  For example, I've seen it with Geo Shells, Geo Shells should never intersect, should they?  Or can it happen with HD morphs?  Would this help here, or is there a different setting?
• mmalbert Posts: 412

  September 2017

  JODel, I don't have any stocking shaders, though that would've been useful for this. I had an old set of stocking leg texture for V4, which would've worked on the Genesis figure I used, but the skin tones wouldn't have matched. (I bought that set some ten years ago and at the time never considered it would be of such limited use. Oh well. Live and learn.)

  I ended up adding a layer of black, at 75% opacitiy, over the K4 leg texture and then saved the end result as a new texture map. It eliminated the thick line along the leg edges and no blotchiness. My little devil doll isn't really needing closeup realism anyway.

   

  

  

  LilDevilDoll.png

  750 x 1060 - 824K
• Richard Haseltine Posts: 108,060

  September 2017

  Does increasing the GeoShell's Push Modifier offset help? As far as I know if there's HD on the base there's HD on the shell, but that would'nt necessarily guarantee no self-intersection
• Oso3D Posts: 15,085

  September 2017

  Displacement map differences between layers can cause clipping.
• dracorn Posts: 2,353

  October 2017

  JOdel said:

  If you aren't showing the edges and toe caps, or need seams, you can just use shaders. I can't remember which packages have stocking textures, but there are some, even though most of them are for Iray. 

  In a pinch you can select the legs and feet in the surface tab, apply a bump from some stockings that you already have and adjust color to match.

  It's a bit of a mess to undo, but you can just save that particular copy in case you ever need to use it again. Doesn't work for lo-cut shoes where you'd be seeing the toe caps, but that example you've got would probably work.

  ETA: unless you want the wrinkles around the knees and ankles. Those need actual stockings.

  I use this one for 3Delight:

  https://www.daz3d.com/morphing-pantyhose-for-genesis-2-female-s