Tweaking Trans Maps for Daz/Reality using GIMP?

3DthiSS

hi all

apparently some transparent maps  are not designed for Lux rendering due to "large dead spaces that do not fall off to pure black quickly enough" and "while other rendering engines may be able to ignore miniscule amounts of color, LuxRender is highly sensitive and will translate material qualities on any thing above pure black"

I have no idea what that means but have been trying to figure out these directions in order to get better looking hair in Reality/Daz.

"To fix this issue, you have to adjust your transparency maps. I use Photoshop to fix this, but any graphic editor with the ability to darken and increase constrast can do the basic job. First you'll want to lower the value of dead spaces to that they are actually black. In Photoshop, an easy way to do this is to duplicate the original map layer and set the new duplicate layer to multiply. I prefer, however, to select the highlight range, create a layer mask, and then create a layer of pure black beneath it. This ensure that black is achieved and gives you options for adjusting the map later on."

I don't have Photoshop just GIMP ....I did duplicate a trans map for the Hampton hair and set it to "multiply" however I could see no difference in tests between this and the original trans map...I picked this hair as that was what the fellow who wrote the comment I've been quoting used as an example and according to him has a trans map that needs tweaking for Reality/Daz.

so does anyone know how to select the highlight range, create a layer mask, and then create a layer of pure black beneath it using GIMP?

thanx

 

 

Havos

Probably the easiest way is to use the magic selection thing to select the mask (it looks like a wand on the tool box), and then fill the selected area with black. Or, if the original mask that is not quite black uses the same color for the whole mask, then you can use select by color to select all the almost black pixels, and then fill this with true black.

3DthiSS

have looked for the "magic selection thing" but can't find it....have posted a pic showing the toolbox interface ....are you able to point it out to me?

sriesch

Possibly Havos is referring to the "fuzzy select tool"?

3DthiSS

AND how does one know if the black isn't black enough?...this is all very confusing and to tell you the truth I'm not even sure what a trans map does..lol..been googling and have found some good simple explanations like the following

"Transparency maps are grey scale textures that use black and white values to signify areas of transparency or opacity on an objects material"

so these trans maps are to make the hair look somewhat transparent?...simple as that?

3DthiSS

sriesch

thanks for posting a larger shot of the toolbox....and hopefully someone else can confirm your suggestion....I'm new to GIMP and am not too familiar with the tools.

sriesch

A transparency (opacity) map makes parts of the image either partially or completely transparent. 

To quickly see how it works, create a plane primitive, then using gimp make a black image and draw a shape on it in white, then a second shape in grey.  Use this as the opacity map on the plane, render and see what happens.

Any place where you had black, the plane is invisible.  Any place you have white you can see those pieces.  Anything that's grey you can see, but you can sort of see through it, more if it's darker, less if it's lighter.

Havos

sriesch said:

Possibly Havos is referring to the "fuzzy select tool"?

Correct, sorry that I got the name wrong.

sriesch

For transparency mapped hair, the idea is that instead of individually modeling and arranging hundreds of thousands of hairs, you can just fake it good enough by making a few basic shapes, then drawing the strands of hair on the image, with a corresponding transparency map so only the hairs are visible and the spaces between the drawn hairs are invisible.

3DthiSS

Havos

ha no worries thanks for replying....ok so that's the tool I'm to use.

all right so I have the trans map loaded into GIMP and I've selected the "fuzzy" tool.

what's the next step?

Havos

Set the foreground color to black (it normally is by default), and then Edit->Fill With FG Color

Now save the map, and it should be a fully black transparency

Edit: I should have said first, to click on the mask area with the fuzzy tool to select the mask. You should see the mask highlighted with a dotted black and white line

3DthiSS

have followed your suggestion...does this look right??

Havos

No it does not look right, the maps before and after should look identical to the human eye, since all you are doing is changing the level of the black in the transparency. You are likely selecting too much with the fuzzy tool. You should only be selecting the black areas.

3DthiSS

yeah that didn't seem right...ok so I've used the fuzzy tool and have selected a black area on the top of the map however the black on the right side of the map does not seem to be selected whereas the left side does seem to be selected.

3DthiSS

sorry that last pic was too small ...here's a large one showing what I was talking about...the black on the right seems not to be selected....is that a problem?

Havos

You can do it in two steps, select the right side, set this to true black, and then do the left side. Alternatively use the fuzzy select tool whilst holding down the shift key, and this adds to the selected area, so you can select both areas together.

3DthiSS

right on I think I got it now....thanks

3DthiSS

well this is a bummer...have just run a few tests and there's no difference between the stock trans map and the tweaked map.

I wonder if the foregrournd color is set to black?...I didn't know how to check and since you said it is by default I just went ahead and tried.

err... I hate to be a pain but how do I check the foreground color?

3DthiSS

all right think I found how to set the foreground ...through Tools-Default Colors.

SimonJM

For maps that are more sensitive than most to greyscale (displacment and transparency) I'd strongly suggest not saving as jpeg as the lossiness you get through compression can disrupt the required effect and blur things (white not being 'full white', etc.)

3DthiSS

SimonJM

what format do you suggest to use?

 

 

3DthiSS

sriesch

thanks for the suggestion of the quick demonstration of how trans maps work....a few weeks ago I taught myself how to use GIMP and created several skin maps with some custom tatts using the transparent layers available in GIMP and that's about the extent of my GIMP experience/knowledge....so I have some idea of how to stack the transparent layers and how the images will appear depending on what order the layers are stacked etc.

so to follow your example how do I create a black image?...I've created a new image through File-New but am unable to turn it black...and once I do have it black what tools do I use to make the white and grey images?

edit  saying I taught myself how to use GIMP is of course wrong...I've barely even scratched the surface.

SimonJM

I'd use png as the file format. Try a flood-fil of the new canvas with full-black (0,0,0,) as the selected colour.  I am rubbish with any graphics application, but I'd set a base layer to be all black or all white, depending on the base requirement (majority transparent or opaque) Once you have that just select the relevant colour for your drawing tool (255,255,255 for full-white, and shades of grey for in-between).  You may want to select the file image mode to greyscale if doing 'just' a transparency or bump/displacement map.

3DthiSS

thanks for the quick reply.

ha you think your bad at using these programs....how do I flood fill my new image and once it is filled what tools do I use to make the images for the example of how trans maps work?

Edit I've figured out how to do this ...thanks

sriesch

The "bucket fill tool" (paint can icon) is floodfill. Select it, then click on your canvas with whatever you have selected as the current color.  (assuming you select black and your canvas is a blank single color, it will simply change the color of the entire thing to black.)

If you want to just draw a random freeform shape on the canvas, change the current color again (to white, or grey for example), then click something like, say, the pencil or paintbrush tool, then just draw on your canvas.

When you are done creating your test image, save it as a .png or .jpg or something, which you will do with file > export.  (not file > save, oddly.) if you want to change the file type, just backspace over whatever the default file extension is and and type the appropriate file type (.jpg, .png, etc) and then when you go to save, gimp will save it as that file type.

 

3DthiSS

yeah I was able to try the quick trans map demo you suggested..ha that's cool.

and I was wondering if you or someone could give a brief description of how a hair trans map is utilized by a rendering engine....I mean I understand the basics now but what do the images on a hair trans map actually represent?...maybe that's asking for too much but it would probably help me to understand what I've been trying to accomplish.

what does the black on the bottom,sides and the  jagged black on top actually represent?

sriesch

It would depend on how the image is mapped to the object.  Your image may be stretched to fit over your object (imagine it as a super-stretch rubber sheet that you would try to wrap around the hair object, so some parts will be very distorted and other parts might get folded in and unused), or pieces of your image might be cut out and applied to your object, or both.  I would guess that the frayed edge along the top of your image is probably the loose strands of hair at the very bottom of your hair, and the tiny edge along the bottom of your image might be along the scalp line. 

A quick easy way to test it is to paint a few random different colored spots on a copy of your transparency image, then use that as your diffuse image instead.  You can then see where each different spot is physically located on the hair.

sriesch

Also you could try looking at both the diffuse image and the opacity image side-by side.  It may or may not help illustrate.

3DthiSS

sriesch

thanks for the info and I will experiment as you suggest.

as well I was wondering if there's a way to check the "purity" of the blackness to see if a hair trans map ought to be corrected....could I use the "color picker" with the "use info window" checked to find out?

sriesch

Honestly I'm not sure about the purity thing or your original question, somebody else will have to answer that one.  It does look like your color picker with use info window can tell you whether or not any selected pixel is in fact completely black, I'm just not sure what you will be doing with that information.

3DthiSS

that's ok I appreciate your help.

and I know this is probably not the best forum for Reality/Daz questions but the Runtime forums are closed.