[itai bachar]

Hi all
Been playing around with Maxwell, but now I want to master it!
Im trying to understand some basics,
First question is how to do a specular, say for a road.
1 - I do a base layer, with the color map.
2 - second layer, additive, acting as the specular, black color, Nd say 1.5-2, force fresnel, and Layer opacity 5% as it is way to glossy/bright,
now for my dilema, with a roughness map or leave it empty?
3 - Global parameter bump map as Normal.

this image is without roughness map:


this image is with roughness map, looks too shiny:


So what is the correct way to do specular map?
thanks
Itai

[tom]

The amount of specular opacity and specular roughness are totally different things. Roughness controls how rough/diffuse your reflections are and opacity controls how much you blend them on the base material. So you should find a good balance for the desired look. There is no such rule and it totally depends on the purpose. But basically, low roughness and high opacity will make it look wet while, high roughness and low opacity will make it look dull...

[arch3d]

If you use specular map in opacity slot for reflections layer you got very nice result

[tom]

Right. And of course please avoid overusing that opacity map as a reflectance map at the same time.

[itai bachar]

Ok, I think Im progressing, , here i'm not using a roughness map, which got me confused,
and only an overall bump:

roughness 03 (to the 'specular' layer) (very slow to render)


here roughness 20, which gives a bigger specular area:


and a dull 50 roughness: (faster render)



on the whole, the roughness map is to be used when there is no bump?
like here?:

thanks
itai

[itai bachar]

Right. And of course please avoid overusing that opacity map as a reflectance map at the same time.

huh?... im trying to understand what you mean...
what is a reflectance map?

here i used the SPEC map in the opacity of the SPEC layer, as arch3d suggested:
it does look intresting!

thank you all!

[arch3d]

Try to connect same SPEC map to roughness slot and invert it. For lambertain materials keep high value (around 90-100). Polished materials you get with 0-25.
Most of cases i dont use nd>1,51 eg.for plastics 1,2-1,35 stones 1,15-1,25

[itai bachar]

Try to connect same SPEC map to roughness slot and invert it. For lambertain materials keep high value (around 90-100). Polished materials you get with 0-25.
Most of cases i dont use nd>1,51 eg.for plastics 1,2-1,35 stones 1,15-1,25

the inverted roughness together with the layer opacity?.. im a bit lost again...
what does the inverted roughness map achieves?
here it is, im not sure i did it correctly,
thanks

[arch3d]

You got specular map in opacity slot. So bright parts of spec map are more reflective.

If you invert same map in roughness slot you will have sth like this:

bright parts of spec map are more reflective and got lower roughness (because you invert map)

I hope you know what i mean:P

[itai bachar]

no, sorry, this goes above my head...
I understand the layer opacity, for limiting the area of the specularity.
But I dont understand why you put the specular map in the roughness, inverted, to do what?
increase the amount of specular in the areas that the Layer Opacity map is blocking?...
This seems like an opposite action..
thanks

[arch3d]

Same here. Roughness is limited by map. Reflection map is from 0 to 255 (not 0 or 255 ) so it has a lot of greys.
Reflections - high values more reflective.
Roughness - lower value more "polished"
Reflective material got high refl and low rough

I know its hard to understand it at the beginning. Do some tests with black & white (0 and 255) reflection map to see differences maybe it will help.

http://support.nextlimit.com/display/ma ... Properties

You can also set a black and white texture to control the roughness. Brighter values in the texture create a higher roughness (a more diffuse surface). When using a texture, the roughness number just applies to the maximum roughness needed.

Tom do i understand it correct?

[itai bachar]

Same here. Roughness is limited by map. Reflection map is from 0 to 255 (not 0 or 255 ) so it has a lot of greys.
Reflections - high values more reflective.
Roughness - lower value more "polished"
Reflective material got high refl and low rough

I know its hard to understand it at the beginning. Do some tests with black & white (0 and 255) reflection map to see differences maybe it will help.

http://support.nextlimit.com/display/ma ... Properties

You can also set a black and white texture to control the roughness. Brighter values in the texture create a higher roughness (a more diffuse surface). When using a texture, the roughness number just applies to the maximum roughness needed.

Tom do i understand it correct?

thanks, i'll try it as you say,
but i dont see a "reflection" map in maxwell.

[arch3d]

thanks, i'll try it as you say, but i dont see a "reflection" map in maxwell.

reflection map = specular map in opacity slot

[Mihai]

on the whole, the roughness map is to be used when there is no bump?

As surfaces rarely have the exact same amount of roughness across their surface, a roughness map allows you to add some subtle variation, so some parts will be maybe roughness 13, others will be 16, others will be 12 and so on, with smooth gradations between these values because you would be using a greyscale map, not just full black or full white.

When you use a roughness map, the roughness numerical value still plays a part - the value you set it to will be the max roughness value represented by the brightest white in your roughness map. If you set the parameter to 30, then 255 white in your roughness map will equal roughness 30, and all darker values in your map can only be lower roughness than that. Set it to 90 and now that 255 white will represent a roughness of 90 and so on. So you have "expanded" the range of possible values.

The difference between "mapping" the roughness using a roughness map, OR using a specular map as an opacity mask in a second shiny layer set to additive?

Think about it for a second and the differences will be clear:

Using an opacity mask in a second layer, will only make that rough reflection appear stronger or weaker. It will NOT change the roughness amount. Only a roughness map will do that. Which one to use depends on the situation, but most likely you will find that you will have a need for a roughness map to vary the roughness, and on top of that also an opacity mask for this specular layer to make the specular reflections even more natural and less perfectly ordered. It's all about control and subtlety, not necessarily "rules". Specular is extremely important, if not the most important aspect to get right in a material, so look closely at materials around you to determine how to best mimic those reflections. Everything has varying roughness - even a piece of paper, and nothing is fully lambert.

Lastly, you can think of roughness as a bump but on a microscopic level. It can be difficult to create a very high resolution bump to recreate the effect that micro roughness would have, but it's entirely possible. So, bump map = bumps on a medium to large scale, roughness = bumps on a microscopic scale. Again, look closely at the real world material you are trying to create. Most times you will be using both roughness and bump.

(I would turn down the bump on that asphalt material)

[itai bachar]

on the whole, the roughness map is to be used when there is no bump?

As surfaces rarely have the exact same amount of roughness across their surface, a roughness map allows you to add some subtle variation, so some parts will be maybe roughness 13, others will be 16, others will be 12 and so on, with smooth gradations between these values because you would be using a greyscale map, not just full black or full white.

When you use a roughness map, the roughness numerical value still plays a part - the value you set it to will be the max roughness value represented by the brightest white in your roughness map. If you set the parameter to 30, then 255 white in your roughness map will equal roughness 30, and all darker values in your map can only be lower roughness than that. Set it to 90 and now that 255 white will represent a roughness of 90 and so on. So you have "expanded" the range of possible values.

The difference between "mapping" the roughness using a roughness map, OR using a specular map as an opacity mask in a second shiny layer set to additive?

Think about it for a second and the differences will be clear:

Using an opacity mask in a second layer, will only make that rough reflection appear stronger or weaker. It will NOT change the roughness amount. Only a roughness map will do that. Which one to use depends on the situation, but most likely you will find that you will have a need for a roughness map to vary the roughness, and on top of that also an opacity mask for this specular layer to make the specular reflections even more natural and less perfectly ordered. It's all about control and subtlety, not necessarily "rules". Specular is extremely important, if not the most important aspect to get right in a material, so look closely at materials around you to determine how to best mimic those reflections. Everything has varying roughness - even a piece of paper, and nothing is fully lambert.

Lastly, you can think of roughness as a bump but on a microscopic level. It can be difficult to create a very high resolution bump to recreate the effect that micro roughness would have, but it's entirely possible. So, bump map = bumps on a medium to large scale, roughness = bumps on a microscopic scale. Again, look closely at the real world material you are trying to create. Most times you will be using both roughness and bump.

(I would turn down the bump on that asphalt material)

Great explanation, now I get it!
thanks