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Original Poster
#1 Old 3rd May 2021 at 8:38 PM
Default Grey lines on hair when using 'Curves' in Gimp?
Hello everyone!

I'm having an issue recently with using Curves in Gimp. I downloaded some pooklet colours made for Gimp, for recolouring hair, which are really good

I'm following the instructons from here

However, I sometimes have an issue with grey lines appearing on my textures when I use it. It's most noticeable on blonde hair, but can show up on grey, red, brown and black too. I've attached a picture so you can see.

I can work around it sometimes by fiddling in Gimp, sometimes using Curves on the texture files from a Bodyshop project and 'cutting' using Transparency > Add to Selection works, sometimes it doesn't, sometimes using Layer via Cut works, sometimes it doesn't, sometimes redoing Curves works, sometimes it doesn't. But this is very time consuming, as you can imagine.

Does anyone know what is causing this, and how to fix/avoid it please?

I feel like I might be missing something obvious, does anyone know please?

Thanks to anyone who can help
Mad Poster
#2 Old 4th May 2021 at 12:22 AM Last edited by simmer22 : 4th May 2021 at 7:00 AM.
Not entirely sure, but some color changing methods can cause these kinds of issues because it removes some of the color information and/or some of the light/dark information. I don't know if Curves does this in Gimp, but there are some tools that you have to apply with some caution in Photoshop (Levels is one - it's often seen in tandem with Curves). Guessing these tools work somewhat similar in Gimp, so they probably have some of the same "flaws" as well.

Not too familiar with Curves used as "actions" but it does look like some of the textures are slightly washed out, so I guess the result would depend on this? Do you have pictures of the texture and sim when it looks fine, compared to the texture when it looks like now?

Used right, the tools tend to work fine, but if you apply too much you'll get flat or somewhat strange colors (Curves will for instance tend to go a bit overboard if you drag the curve all the way to the top/bottom).

Bodyshop's compression could potentially also be an issue - extract the original texture with SimPE if you're worried about this. Probably not the problem, but who knows?

Gimp also has the issue with file saving, but you probably already know you have to save the files as a particular file format. Can cause weird things to happen to textures if not followed. Maybe worth checking just in case.


EDIT: Tested out the curves on the provided base textures, and while I can see a little bit of the washed-out issue in the highlights and darker areas, there's no grey on the textures themselves. Haven't tested in Bodyshop, though. Could be an artefact if you don't save the Gimp files with the proper format, maybe - or if you use the curves on a different texture than the base textures provided?

Also, which textures are you working on? If you extract from SimPE and get one that already has an alpha applied, you may get some problems around the edges. Working on textures directly from Bodyshop or applying a white alpha in SimPE gets you a full texture, which could help if the problems happen around edges.

If problens happen on some hairs but not others, make sure you're applying the curves on a Pooklet Volatile base - using anything else would most likely result in a different color even if what you have looks very much like Volatile.
Original Poster
#3 Old 5th May 2021 at 11:59 PM Last edited by Dizzy-noodles : 6th May 2021 at 12:15 AM.
Thanks for replying, sorry I'm a bit late replying back.

I'm feeling a bit disheartened by this issue, because I thought these hairs were finished and ony noticed the other day. I need to go back into my game and see how many hairs are affected.

I did have the problem a few times whilst making the hairs, but thought I'd fixed them all - the trouble is, it takes me ages each time, because I haven't found a consistent solution yet, I just have to mess about and try everything, then it seems to be random, what worked for one hair won't work for another and vice versa.

I don't think I have a picture of the texture when it is fine, but I will dig about and have a look.

I don't actually touch the settings at all when using Curves in Gimp , I do this:
1. Open volatile texture in SimPE and export the texture as a PNG
2. Open Gimp and open up the PNG
3. Go to Colours > Curves > click the arrow by Presets > Import Settings from File
4. A list of pooklet colours opens, so I click on the colour I need and press OK
5. The hair on the PNG changes colour (at this point it looks fine, whilst trying to establish the cause of the issue, I have tried placing a background of the same colour on a lower layer, and magnifying it, to see if I could see the lines, but you can't see any lines at all)
6. I export as a PNG, from Gimp
7. I use Build DXT in SimPE, (I use DXT5 and Sharpen is set to None) Commit and Save as normal and put the file into my game

I do sometmes resize the PNG in Gimp, as many are blurry in my game at 512x512, so I make them 1024x1024 instead.

I never use Bodyshop if I can help it, so using SimPE is my method of choice.

Yeah, using Curves doesn't work well on the lighter areas of the hair, such as highlights, you definitely lose some detail.

The lines don't appear in the middle of the sections of hair on the texture, they appear around the edges of each section of hair where it meets the transparent parts (I've roughly scribbled on a hair texture in red to show you where I mean, and added a picture of a male hair I half-started the other day (I have to admit I saw the lines, and sighed, and left it to fix another day)). I worked this out because I only get them where sections of hair overlap each other. I call them 'grey lines' but they are probably actually volatile - I use incendiary as my preferred blonde, so volatile probably would look grey on top of incendiary.

I can't see the issue in Gimp itself, SimPE or in Bodyshop - I can only see it is CAS, when zoomed in on the head (you can't see it from the view when changing clothes, for example).

Do you know which settings I should use when Exporting as a PNG in Gimp please? I just use the default settings, I've never changed them (I've attached a picture of them).

Also, which textures are you working on? If you extract from SimPE and get one that already has an alpha applied, you may get some problems around the edges. Working on textures directly from Bodyshop or applying a white alpha in SimPE gets you a full texture, which could help if the problems happen around edges.

I'm using textures extracted from SimPE. The problem is the edges. How do you apply a white alpha in SimPE please, I haven't tried that?

I have tried making a project in Bodyshop, opening one of the texture squares, exporting it as a PNG, opening it as a layer, and cutting out the hair using the PNG as another layer as a guide (using Select by Transparency in Gimp) - that's another thing which sometimes works, sometimes doesn't.

I have tried using one of the alpha squares from a Bodyshop project before, but I find the fuzzy select, or select by colour, not very accurate, it either doesn't pick up all the black, or doesn't pick up all the white. That's why I tend to use the PNGs I've exported from SimPE instead.

Thanks for helping me, you're very patient I feel like I'm missing something basic/obvious, like someting in the Gimp settings perhaps?
Mad Poster
#4 Old 6th May 2021 at 1:31 AM
It shouldn't be a problem with PNGs, but what import method are you using? You need to use either DXT3 or DXT5, and "none" for sharpen.

You can import/export an alpha in SimPE, but I've had mixed results with that (sometimes it ends up grainy). You right-click on the texture and should get the option to export and import an alpha texture. Can be useful if you want to extract and edit it for Bodyshop purposes, though.

You can also use DDS files (they allow for alpha editing in the DDS file), but I've had mixed results with those as well (and they can occasionally be a pain to edit).
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