I was looking at examples that had "speckled dirt" or dirt patches on them. It can be hard to see in some pictures.
When I multiplied a dirt texture on it, it looked like a flat 2D sticker.
If I do this for the albedo, does this mean I'll also have to make changes for the metal map (i.e separate colors for grunge and metal) or is it ok to just leave the metal with grunge multiplied on it?
You have to start to learn how to break down these materials and experiment on your own. Experimenting, messing around with your maps, and just trying stuff is the best way to learn. You are not going to get all the information you need from the internet. Unfortunately I do not have time to make you another example, but hopefully this will help you a little bit.
I try to break down my materials before I start texturing. This just gives me a quick start and blockout, which will let me know if I am on the right track or not.
For the dirt, I break it down like this:
Albedo: Similar value to the paint, parts of it are lighter.
Metalness: Not a metal
Roughness: Very blurry reflection value, which for UE4 would be a value of 210-225 out of RGB 255.
Normal: Would have a grit to it, that would stick out above the paint.
For the patina/wear on the metal I would break it down like this:
I like to find close up material ref when I texture stuff, for steel I found this one: There are 3 main elements to this texture. The steel, the dark dirt, and the rust.
The steel has these properties:
Albedo: Its true albedo value is super dark, but because you are using the metalness workflow this will be the reflectivity value. The metal is overall bright, so its value will be fairly bright. Somewhere in the 175-210 range. Then make some of those scratches a higher value so they catch that those bright highlights.
Metalness: Yes it is a metal.
Roughness: The reflection is semi clear, not crisp clear, but it is noticeable. A roughness value of 120-80 would be a good place to start.
Normal: Very little normal detail, can add the scratches if you want.
The dark dirt has these properties:
Albedo: Dark value, looks like some type of carbon dust, so a albedo value of 70-80 would be good.
Metalness: Not a metal, but might looks better with a little boost in reflectivity, try to experiment with that.
Roughness: Super rough surface. Would be around 200-220 in UE4.
Normal: Not much normal contribution. Could put some noise in the normal map for it, but might read better without it. Try to experiment.
The rust has these properties:
Albedo: Lighter value than the dirt, but not by much. A value of 100-120 is good for rust usually.
Metalness: Not a metal, but similar to the dark dirt it might look better with some subtle metalness effect.
Roughness: Rough surface, probably close value to the dirt, but to break up the surface I would make it either higher or lower.
Normal: Will have some grit to it that will need some normal noise.
Note that these values are rough overall values guesses. You will have to tweak and check our texture to find out what works best.
Yep, you will have to change each map to reflect what material is being represented on the model. Think of it like this (this is very simplified explanation and I'm just saying it off the top of my head)
You have some perfectly clean metal, all correctly reflecting and looking awesome.
Then some mud gets splatted across it. Some of that clean metal is still visible but a lot of it is completely hidden.
Your Albedo will need the colour information changed where the mud now is.
Your Metalness will need to change as there is only metal on certain parts of the texture, as the rest is mud. If you don't change this it would make your mud appear way too reflective and basically like metal.
Roughness, now depending on how wet the mud is, or if it has dried this may vary, but I would say it would be different to the metal underneath, so play with this until it looks right for what you want to achieve.
Normal map will need to change as its unlikely you will have perfectly smooth mud. You will want this to probably look as if it has been splatted, so it has some velocity, especially if your going for wet looking mud.
Ambient Occlusion, this will change because the mud has thickness, and possibly some depth, so you will need to represent this, this will depend on the normal map so use that as a guide.
I read a book called "Texturing & Painting by Owen Demers" he speaks a lot about the story of the material, and how if you think about where and what has happened to a surface, you will be able to create a better material.
So for example, your barrel was once pure clean metal, then it was formed in a press, welded together, painted, possibly shipped to where the oil is (while it was on the ship it might have been exposed to some salty air and water causing it to rust), filled with oil, then shipped off again to somewhere, flung on the back of a truck denting it a little, opened up and poured into some small jerry cans, slopping the oil/petrol down the side, which reacted with the paint and caused it to lift and erode. Now its sitting in a desert empty and slowly rusting away.
Think of each stage of the journey as a separate pass on your texture, start with clean metal, add the paint, wear it away a little and expose some rust, then add dirt and mud that has accumulated on it.
This might be a bit of a read, but I hope it helps.
Replies
You have to start to learn how to break down these materials and experiment on your own. Experimenting, messing around with your maps, and just trying stuff is the best way to learn. You are not going to get all the information you need from the internet. Unfortunately I do not have time to make you another example, but hopefully this will help you a little bit.
I try to break down my materials before I start texturing. This just gives me a quick start and blockout, which will let me know if I am on the right track or not.
For the dirt, I break it down like this:
Albedo: Similar value to the paint, parts of it are lighter.
Metalness: Not a metal
Roughness: Very blurry reflection value, which for UE4 would be a value of 210-225 out of RGB 255.
Normal: Would have a grit to it, that would stick out above the paint.
For the patina/wear on the metal I would break it down like this:
I like to find close up material ref when I texture stuff, for steel I found this one:
The steel has these properties:
Albedo: Its true albedo value is super dark, but because you are using the metalness workflow this will be the reflectivity value. The metal is overall bright, so its value will be fairly bright. Somewhere in the 175-210 range. Then make some of those scratches a higher value so they catch that those bright highlights.
Metalness: Yes it is a metal.
Roughness: The reflection is semi clear, not crisp clear, but it is noticeable. A roughness value of 120-80 would be a good place to start.
Normal: Very little normal detail, can add the scratches if you want.
The dark dirt has these properties:
Albedo: Dark value, looks like some type of carbon dust, so a albedo value of 70-80 would be good.
Metalness: Not a metal, but might looks better with a little boost in reflectivity, try to experiment with that.
Roughness: Super rough surface. Would be around 200-220 in UE4.
Normal: Not much normal contribution. Could put some noise in the normal map for it, but might read better without it. Try to experiment.
The rust has these properties:
Albedo: Lighter value than the dirt, but not by much. A value of 100-120 is good for rust usually.
Metalness: Not a metal, but similar to the dark dirt it might look better with some subtle metalness effect.
Roughness: Rough surface, probably close value to the dirt, but to break up the surface I would make it either higher or lower.
Normal: Will have some grit to it that will need some normal noise.
Note that these values are rough overall values guesses. You will have to tweak and check our texture to find out what works best.
You have some perfectly clean metal, all correctly reflecting and looking awesome.
Then some mud gets splatted across it. Some of that clean metal is still visible but a lot of it is completely hidden.
Your Albedo will need the colour information changed where the mud now is.
Your Metalness will need to change as there is only metal on certain parts of the texture, as the rest is mud. If you don't change this it would make your mud appear way too reflective and basically like metal.
Roughness, now depending on how wet the mud is, or if it has dried this may vary, but I would say it would be different to the metal underneath, so play with this until it looks right for what you want to achieve.
Normal map will need to change as its unlikely you will have perfectly smooth mud. You will want this to probably look as if it has been splatted, so it has some velocity, especially if your going for wet looking mud.
Ambient Occlusion, this will change because the mud has thickness, and possibly some depth, so you will need to represent this, this will depend on the normal map so use that as a guide.
I read a book called "Texturing & Painting by Owen Demers" he speaks a lot about the story of the material, and how if you think about where and what has happened to a surface, you will be able to create a better material.
So for example, your barrel was once pure clean metal, then it was formed in a press, welded together, painted, possibly shipped to where the oil is (while it was on the ship it might have been exposed to some salty air and water causing it to rust), filled with oil, then shipped off again to somewhere, flung on the back of a truck denting it a little, opened up and poured into some small jerry cans, slopping the oil/petrol down the side, which reacted with the paint and caused it to lift and erode. Now its sitting in a desert empty and slowly rusting away.
Think of each stage of the journey as a separate pass on your texture, start with clean metal, add the paint, wear it away a little and expose some rust, then add dirt and mud that has accumulated on it.
This might be a bit of a read, but I hope it helps.