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How to use displacement map in combination with normal map?


Medler
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If I understand it correctly, using the normal map and displacement map combined, the displacement map does the heavy lifting of adding in mid level details and the normal map does add in the real fine details, that otherwise would add retarded amounts of render time with the displacement map alone? 

What I mean to say is that anything that doesn't effect the overall silhouette of the model should be stuffed onto the normal map (as its great for this), and any major shape changing of the model should be left to the displacement map. This way you have the ideal situation.

 

Am I correct? If so: what would the workflow in 3d coat be?

 

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I have an additional question:

 

Is it best, for an optimal use of the displacement map, to make a retopo mesh with as much of regular divided polygons as possible? Is it correct that if the retopo mesh is even divided, the displacement map can be optimal subdivided with minimal los of details in other 3D packages? 

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Yes, you need to have enough geometry to support the physical changes displacement maps influence.  However, it depends on your goal.  For instance, if you're doing game art and you know generally where your displacement is going to happen in the model, then you might consider focusing on having more polys in those areas and not others, to ensure the lowest necessary poly count.  The time that takes you will also drive how important that step is.

 

Normal maps fake actual geometry and appear to be affected by light

Displacement maps influence the position of existing vertices to cause physical change

 

I often don't even bother with displacement, but rather ensure the topology reflects the physical changes, but for very complex models, displacement can take far less time and give better results.  You can bake normal and displacement maps from the Texture Baking Tool in the Paint room under the Textures menu.  As you mentioned, you need to ensure enough geometry to support your displacements via the Retopo room or by subdividing your mesh.  The latter method is likely going to cost you less time, but more polys.

 

One benefit of displacement maps over bump maps is the way your normals face can really affect how well your normal maps work.  Displacement, is simply...well, displacement.  You either have enough polys in the right areas or you don't.

Edited by alvordr
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Ok, than I am on the right course of understanding displacement maps in combination with normal and/or bump maps :-)

At this moment I am into very detailed landscapes / terrains, so displacement maps would be a huge benefit for me.

 

By the way is the difference (apart from technical differences) between a normal map and a bump map, that a normal map is for fine details and a bump map for super fine details? Or are they for the same level of details and are they just complementing each other?

 

And how does this insight affect the regular workflow of 3d coat?

Does 3d Coat bake mid level details to the displacement map and the fine details to the normal map automatically?

If so, are there functions/buttons to activate (select / push)?

Is "merge for per pixel painting with displacement" the best workflow for a optimal combined displacement and normal map, or does it require a special approach?

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Yes, for landscapes, I would definitely use displacement, especially if you're going to do any kind of close-up work or walking around on that terrain, etc.  As to what the difference between bump and normal maps are, think of it this way:

 

Bump maps are usually used in a similar way to displacement, and concentrates on large details.  They are gray-scale images, where the lighter areas are raised and the darker areas are recessed.

Normal maps are used to fake details in a way that light actually affects the way they appear, but no actual geometry is deformed.  They are RGB images, which is why you sometimes have to flip a the green or red channel, etc., depending on what you're bringing your normal maps into.

 

Sometimes, 3D software calls bump maps, normal maps, or vice-versa.  It's not technically interchangeable, but there you go.

 

So, in the example of a landscape, you could use a displacement or bump map to dictate how major deformities in the land actually occur, where you might then use a normal map to indicate rocky terrain vs smooth terrain.

 

The workflow in 3D Coat is often the tick of a simple check box or two to decide whether or not you want to generate a displacement map or not.  When using displacement, you'll be asked to smooth the mesh or subdivide it to support the deformations that are to occur.  This means your poly count goes up for displacement.  I'm not sure how 3D Coat bakes the details, as that question is aimed more for Andrew.  If you want to send an asset from the Retopo room to the Paint room and generate displacment, consider this option, under the Retopo menu:

 

mACctY5Kc7MCy5au-Region.png

 

...or in the Paint Room, under the Texture menu, go to the Texture Baking Tool:

 

XlJeOM0l9vbyga8D-Region.png

 

...or in the Paint Room, upon export of your asset:

 

Odz9BjtTGCACui1b-Region.png

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As far as your very last question, you might consider asking Andrew the main difference.  The thing to keep in mind are the hints that pop up as you float over the choices.  For instance, floating over Merge with NM per pixel states that it will bake the normal map, but not displacement, so you'll want to do the one for displacement.  The process, otherwise, looks pretty much the same.

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Thank you very much for all your efforts. I am getting a better idea of how displacement maps can be used in combination of normal and bump maps. Grasping retopo techniques with displacement maps better, makes me thinking, which creates new questions again :-) F.e., is it best practice to use displacement maps in combination of bump maps and also normal maps? Bump maps for the embossing effect (little depth, fine details). And in addition to that, normal maps for a detailed look of depth (medium depth, fine details) for looking at it in a straight angle?


 


I also learn from your knowledge, that if one should decide to go with displacement maps, you rule out gaming and therefor are not restricted to the boundry of  aprrox. 15.000 polys anymore. Because of the high details of my landscape, it's going to be for stills and animation anyway :-). At this moment my low res mesh is about 30.000 polys. To be sure: is this a normal amount of polys (for stills / animations) to start with and subdivide them with displacement maps from there on? Or is it a better thought, to start from around 15.000 polys anyways (if possible) and let the subdividing of te the displacement map do all the work? Displacement maps have another advantage, I assume: you can lower the subdivision of displacement, f.e. if your camera angle is optimal for normal mapping and you can increase the subdivision of displacement when you want a closeup and thus saving a lot of render time while keeping the optimal details that gives a realistic look as possible. if that's the way, it is better I think, to have as few as possible polys in you retopo mesh.


 


Is there a difference between retopo for displacement maps (stills / animation) and retopo for normal maps (gaming)?  If you want the best results out of a displacement retopo map, is it better for displacement maps, not only to have as much as possible even divided polys, but also soft edges while avoiding sharp silhouettes and getting a unrealistic render?


I think this is what 3d coat already does huh? 3D Coat is already softening the mesh, if you select this option, while texture baking from the paint room. So am I nitpicking? Does 3d Coat all the work here, or is better already creating soft edges in your retopo mesh in advance anyway? Doing it yourself gives you also more control.


 


And what about the option "Coarse (sharpen) mesh", if you decide to export (in stead of baking) from the paint room? What's that all about?

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I believe I've mis-communicated a bit here.  Actually, game artists often use displacement, but they think about and try to control how much of an increase in polys they use to achieve the desired effect.  It's most often used in landscapes.  As I stated before, using the landscape example, you can use displacement and normal maps, together.  Displacement doesn't always equate to higher poly counts, but only when necessary to achieve the desired result.  You can have the same number of polys and get nice displacement, but it depends on the topology and the amount of displacement over a set number of vertices.  Landscapes use something called height maps, which are basically displacement maps.  You can look these concepts up with a Google search and find quite a lot of resources on them.

 

You really only need more polys where the changes occur.  To save time, some artists will simply subdivide a mesh to compensate for any changes, while others will look to keep poly counts low and only increase polys in certain areas.  3D Coat does this as you model.  ZBrush does this when you remesh.  However, you can manually retopo to get more conrol.  3D Coat makes that last process a little easier with strokes, but I often find myself going back and redoing some of that result.

 

As far as the coarse mesh setting, please use the hints it gives you and address further questions on that to Andrew.

 

 

NOTE:  Your text is black on the thread, now, so it's hard to see/read.

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One thing to consider is to keep 'displacement' areas on their own islands in the UV map so that the desired increase in polys doesn't apply where not needed. I'm thinking of those areas that will be seen in silhouette. .

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Thank Tony, you give me new insights. Interesting technique, keeping displacement on their own islands in the UV map. But to be honest: I don't know what you mean. I 'm a newbie :-) Can you give some more detailed hints?

 

In the mean time I found some specific information (keep searching Google does pay off :-) ), I am looking for about displacement maps.

For the people who are reading along and also want to know more about diplacement maps:

 

http://www.cggallery.com/tutorials/displacement/ 

Here I learned a.o. about a accurate displacement workflow and how to make 'spot on' precise displacement maps with very high details. Also the format of the displacement map is important. Use a floating-point format (.exr or .tif) instead of a integer format (.jpg or .bmp). 

 

 

http://www.marmoset.co/toolbag/learn/displacement

Here, I learned a.o. that displacement mapping does require a slight different retopo than retopo with pure normal mapping. Not only have the polygons to be as even as possible, they also have to be as square (triangular) as possible (avoiding artifacts). Furthermore you should avoid steep angles, your retopo has to have a soft flow, in order to avoid displacement stretching. Also use as little as seams as possible (or hide them) because bit depth accuracy is a limitation. 

 

Anyway, let me know if 3d Coat has overcome some of this issues.

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