Displacement maps. The words sends shivers down the spine of any CG artist. It’s a topic I’ve spent countless hours trying to wrap my head around. In this tutorial we’ll look at a reliable way to use 32 bit displacement maps in modo generated in ZBrush.  You have significantly more data to work with so your displacement will be more accurate and will contain more information. I’ll assume you know the difference between a normal, bump and displacement map, and why a displacement map is necessary. If not, you have some Googling to do.

The final result

Tutorial

 

 

Let’s get started.

 

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 Here is the mesh in Zbrush which I want to transfer to modo. It's about 4 mill polys and it's fairly detailed. It has been retopologized to make sure that the topology is good, and it has UVs with little to no stretching. It’s extremely important that your UV map is good, otherwise you’re going to see nasty artifacts and stretching in the render once you apply your maps.

Clean topology

Clean and logical UVs

 

 

 Alright, let's jump into ZBrush

We’re going to use Multi Map Exporter (MME), which is a relative recent plugin in ZBrush. You can find it under Zplugin in your top menu. This is your friend and you should know it well. Before we had this thing of beauty, we had to export every map manually, which is a tedious process. With the MME, you can export several maps at the same time where you have more control over them. It also supports multiple UV tiles. This is a huge thing when you’re working in a production and your UVs are laid out over several tiles. Traditionally, multiple tiles are hard and convoluted to work with in ZBrush, so this is wonderful. More info regarding the MME
Tutorial04
Tutorial05 Open the plugin up and you should hopefully not be too overwhelmed by the wall of text and buttons. Check Displacement in the very top. Here you can adjust your size, export map for all visible subtools, et cetera. Set the size to whatever you need, in my case I need a 2k map. Enable Flip V which will flip the maps vertically, which you always have to do in Zbrush due to some weird voodoo by Pixologic. Next, hit the friendly looking button which says Export Options. This is where the options for the various maps can be found. You want to click Displacement to bring up the options for the displacement map. 

 

Now there are a couple of settings which we need to know about

SubDiv Level: This dictates which subD level the displacement map will be generated from. You normally want this set to 1 as the displacement will then be generated from the lowest level, meaning that the map will have the difference between the lowest and highest level. This overrides the current subD level your model is currently in, which means that if your model is set to level 5 and your SubDiv is set to level 1, then the map will be generated from level 1. I sometimes use this to make bump maps. If I set my SubDiv level to 4 out of 6, the displacement generated will only include the finer details, so it can be used as a bump.

 

Adaptive: If pressed, the map will be of higher quality, but it will take longer to generate. I always have this on when exporting a final displacement. I leave it unchecked when doing tests.

DpSubPix: Now this is an interesting one. Initially I thought this was only a quality slider, where 0 was the worst and 4 was the best. It's not.

 

 

Smooth UV: This will smooth your UV, as you might have guessed. Might or might not be preferable, depending on your project. If unpressed, your UVs will be rigid, which might be what you want. By default, modo will smooth your UVs so this might be preferable. In this example though, I will NOT smooth the uvs. It's extremely important that you're consistent here, otherwise you will have issues with seams.

 

Mid: This is the mid range for the displacement. When using 32 bit maps, you want your mid range to be set to 0. By default the mid range will be 0.5, meaning 50% grey, which makes no sense when using 32 bit images.

 

3 Channels:  Will give the displacement information in all channels instead of just the red one. Enable this.

32 Bit: Enable this. Otherwise you cant get a 32 bit map.

Scale: Don’t touch this.

Intensity: Don’t touch. There is a way where you can use the intensity with 32 bit maps, but frankly, there’s no need to do so.

16 Bit Scale: Only relevant when using 16 bit maps.

Get scale: Can be handy, but don’t touch this for this particular workflow.

 

 In short, these are the settings you want for top quality

 

 

 

Now hit Create All Maps and chose the directory you want to save it to. You can only create Tiff files, but they should provide you with sufficient data. Give it a couple of minutes and you should be set. As a general rule, I never touch the computer while Zbrush is calculating. Sometimes it freezes and crashes when you touch it.   Export your base mesh at the level you want, preferably the lowest one.

 

ProTip

Leave the ZBrush window active while the maps are being generated. This will make the maps generate faster, according to the developer of MME. It will generate regardless of ZBrush being the active window, but it will slow down if you Alt+Tab to something else.

This is what the map will look like. 8 bit maps are very different from 32 bit maps. There is nothing wrong with it even though it might be almost all black.

 

Modo time!

 

 

File - Import and select your Obj file. Organize your file and give the different items appropriate names. This will save you so much trouble later on.

Remember how we made the displacement map with Smooth Uvs unchecked? Now is the time to change this. Click on the mesh item and enable Linear UVs

 


 

 

 

Here you can see the difference between linear and smooth UVs.

Linear

Smooth

 

Lets head over to the new, sexy render layout found in modo 701. Select the model you want to displace, here the body, hit to give it a material. Again, give it a proper name.

Now we need to assign the displacement map to our fishy.  The easiest way is to simply drag it from the explorer to the shader tree. By default it will be set as Diffuse Color. As this is a scalar map (as opposed to a color map) the gamma should be set to 1.0. In other words, dont touch the gamma if you're rendering in linear workflow. If you're not rendering in linear workflow, shame on you; you should.   

This is what it looks like currently. Apparently nothing is happening. Either the map simply isnt working, or it's not strong enough. In this case, it's simply not strong enough.

 

 

This is the million dollar question: How the heck to you know how strong you should set the displacement map to be? What magical numbers work every time? I'm going to be completely honest here: I dont know. In vray, there is a way to do it which works every time, but I havent found anything like this in modo yet.   That said, setting the Displacement Distance to 1 meter seems to work in most cases, but this can vary from scene to scene.

This is with a Displacement Distance set to 1 m, rendered out.

If you want to have better visual results with the displacement, enable Displacement as Bump under Settings

   Map Sizes

As a final note, let's talk briefly about the size of your map. The map size should be directly correlated to your poly count. As an example of this, a 1k map has only slightly over 1 million pixels. If we use it as a displacement map, this means that each polygon will equal one pixel. In turn, this means that you can only displace up to 1 million polys using a 1k map. If you have a 1 million poly mesh and you're using a 4k map, you're then wasting a lot of space.

Here are the map sizes with the polycounts next to it
1 k - 1 mill
2 k - 4 mill
4 k - 16 mill
8 k - 64 mill
This is of course only the theoretical MAX polycount; in reality you probably have to go slightly above this, unless your UV map is using 100 percent of your UV space. If the details in your render are too soft compared to the ZBrush sculpt, this could be one of the reason; your map size is too small.

That’s how you successfully render a displacement map from Zbrush in modo. It's really a rather simple procedure once you know how. If you have any questions or comments, feel free to shoot us an email.

And there we go!

We hope you enjoyed this tutorial. For more head back to theTutorials Section