I'm trying to get a node set-up that has streaks of varying color (my current interest is shades of gray) that run in either vertical or horizontal lines. I have a lot of applications for this, but an obvious one is to add this to a vertical hair color image map to add some variance in the shades of color in the existing bitmap. I'd like to vary the width of the streaks and do this somewhat randomly.

I can kind of show you want I'm talking about by looking at the attached image. I've used the tile node to make vertical streaks. I then add this (multiply actually) to the existing hair image to yield streaks. The trouble is I can't randomly vary the streaks in terms of width or color so the pattern repeats. I think if there was a random number generator node, that might work.

I hope this is clear....

Thanks

Quote - I'd like to vary the width of the streaks and do this somewhat randomly.

A paint program perhaps?  PSP or PS.

Judging by the set up of that map, I don't think it would be easy to do it procedurally.  Particularly if you want any fine or specific deatils.

Quote - > Quote - I'd like to vary the width of the streaks and do this somewhat randomly.

A paint program perhaps?  PSP or PS.

 

Judging by the set up of that map, I don't think it would be easy to do it procedurally.  Particularly if you want any fine or specific deatils.

I have tried a paint program to produce the streaks, but everytime I wanted to vary some part of the pattern, I had to draw a new one. Since it's just vertical or horizontal streaks, I had hoped it could be set up in the material room, but perhaps not.

Have a look at the screen shot.

The u_Texture_Coordinate node gives the U value from the UV map. Similarly, the v_Texture_Coordinate node gives the V value.

In the 3D nodes that have x_scale, y_scale, and z_scale, if you connect any node to one of those inputs, that input stops tracking the 3D value it usually does, and uses what you plugged into it instead.

So here I plugged the U into x_scale and V into y_scale. Since we're going from 3D to 2D, we want the third dimension frozen, so I just plug a math node into the z_scale with a constant value - thus freezing it.

Then, simply change the scale numbers in X or Y and you're changing the U and V scales instead! The pattern you see is like a 2D slice out of the original 3D pattern.

You can change which "slice" you see by changing the number in the math node. Any number works, so if the pattern you see isn't to your liking, try a different number.

Here I used x_scale = .2 and y_scale = .01. That makes the pattern of random but generally horizontal streaks. Reverse those numbers to get vertical streaks.

Try different values in the Bottom and Gain. Higher Bottom will give you more black. Gain controls the overall contrast.

If you actually want two colors, run the output of the fBm into a Blender node. Put two colors in the Blender, and then drive the Blending value with the fBm with the Blending number = 1.

Quote - > Quote - > Quote - I'd like to vary the width of the streaks and do this somewhat randomly.

A paint program perhaps?  PSP or PS.

 

Judging by the set up of that map, I don't think it would be easy to do it procedurally.  Particularly if you want any fine or specific deatils.

I have tried a paint program to produce the streaks, but everytime I wanted to vary some part of the pattern, I had to draw a new one. Since it's just vertical or horizontal streaks, I had hoped it could be set up in the material room, but perhaps not.

Usually what people here think is impossible is at least difficult. This one was trivial.

Thanks for the help.

WinterClaw,

Reading over the thread again, I realized that I may have inadvertantly implied a contradiction to what you said. I meant no disrespect. I was responding to Mark's tentative conclusion that what he asked for was not easy.

I think you mean that getting the streaks to follow a specific curved path is not easy, and that is absolutely true. But Mark didn't ask for that.

In the use case involving this particular hair, the bottom layers are not strictly vertical or horizontal, and procedurally streaking them is a fail.

However, many hairs have two different materials for outer and inner layers, and streaking the outer layers where all the strips are straight is perfectly dealt with here.

Failing that, a trivial mask could be made that removes procedural streaks from the areas where they would contradict what the texture map has in it. Or with some more work, multiple sets of procedural streaks can be combined with masks, so that different angles can be combined into the single UV space. Even diagonal streaks are possible by using U+V and U-V as the driving coordinates. Certain curves that have simple mathematical descriptions are also possible fairly easily. For example, any elliptical path is mathematically straightforward and using matmatic would make the job pretty easy.

A general arbitrary curve would be very tricky, though. Bezier curves or cubic splines are a possibility.

http://www.renderosity.com/mod/rrwiki/index.php/Poser_Shader_Threads

Quote - I think you mean that getting the streaks to follow a specific curved path is not easy, and that is absolutely true. But Mark didn't ask for that.

In the use case involving this particular hair, the bottom layers are not strictly vertical or horizontal, and procedurally streaking them is a fail.

However, many hairs have two different materials for outer and inner layers, and streaking the outer layers where all the strips are straight is perfectly dealt with here.

That's exactly correct. The curved piece of hair in the middle of the example texture map shown above is meant for the scalp piece under an outer layer of longer hair. It's the outer layer I wanted to randomly put streaks or highlights into.  From what I've seen this is a pretty common approach to setting up hairs, so I think this will work fine, I tried it last night and it looks pretty good. The inner scalp layer is usually only seen at the front hair line above the forehead, and only a very small area is exposed.

Perhaps one question I had as pertains to scaling, so let me see if I can phase this correctly. The new streaks apply over the hair texture map, but say I wanted something denser, more streaks per inch. As one extreme example, say I completely eliminated the hair texture map and wanted to show individual hairs. Many more streaks per inch would be required than for the "highlights" I was adding previously. How do I control that density? It may be I don't understand how Poser applies the little map I see at the bottom of the node to the hair texture map. I know the hair map is physically large in terms of dpi by dpi because I can look at outside Poser, but the little "preview" image for the steaks is hard to see. How do I know I'm really adding more streaks by some method? I don't see that there is any tiling option, so control of the density of streaks is unclear. I can see how to make a few big streaks as you outlined last night, but again how does that scale match the scale of the hair map or the object being mapped to? Is that only to be understood by trial and error (try it, render it, change, render again, etc.)

I was told once, if you don't understand, ask. I've always followed that guideance to the point of asking very simple questions some times. I understand this is trivial to talented people, but it helped me, so I appreciate it. I have to leave for work, so I'll be off line for awhile.

Thanks again

Bill, I never would have thought of what you suggested.  My first reaction was try to make verticle stripes using some nodes and use those to mess with color.  The I saw the base of the hair and thought if someone wanted stripes there as well, things would get a hole lot more difficult.

My frame of reference at the time, as it's usually from out of nowhere, was the whole image map and getting maybe 1-2 streaks in specific areas.  I wasn't even thinking about how hairs are usually set up.  Many are for ease of striping, which is why this one would be trivial as you said, but not all are.