TONE MAPPING

This post is requested by Midnight Arrow at bitbucket to explain tone mapping in relation to material conversion. Below there's some reference.

http://www.digitaldog.net/

https://docs.omniverse.nvidia.com/app_create/prod_materials-and-rendering/render-settings_post-processing.html

https://docs.blender.org/manual/en/latest/render/color_management.html

https://bitbucket.org/Diffeomorphic/import_daz/issues/22/basic-tone-mapping

One feature of the diffeomorphic importer is that it converts materials from iray to cycles and eevee. This means that you can reasonably expect that your blender materials will be similar to daz studio. Then lights and cameras are converted as well, together with the notorious ghost lights. So your daz scenes will mosttly retain in blender the same look they have in daz studio.

What is not converted is tone mapping. Because there's no easy way to do it, and also because tone mapping is application specific and usually the tone mapping features are decided at render time depending on the project.

Q1. So what it is tone mapping and how does it affect materials and rendering ?

A1. Well tone mapping is how the rendered image is mapped on the output device. That is, a rendered image is defined in a linear color space that can store all the possible physics colors. Then your monitor can't reproduce all those colors so the rendered image is "shrinked" to fit the monitor palette. Technically this is called a linear to srgb transfer function that's what tone mapping does.

Below there's an example of tone mapping in daz studio with the default settings. We can see that the sphere and the background hdri are partially overexposed. This means that the tone mapping in iray doesn't map those colors in the output space of your monitor and they're all white.

You can find the daz test scene in the bitbucked link above. This scene needs the standard genesis package to be installed, plus it uses the standard srgb reference at digital dog, where you can also find lots of good articles.

Below there's the same scene imported via diffeomorphic and rendered in cycles. Here we use the default filmic view transform that's the blender tone mapping. We can see that the filmic view maps more colors to the monitor and the image is less overexposed.

We can get in blender a tone mapping similar to the iray default by using the standard view instead of the filmic view, with a medium low contrast look. Below there's the scene and the settings. We can see that now the colors and lights are more similar to iray.

Q2. Then why diffeomorphic doesn't force the standard view to mimic iray ?

A2. Because the iray tone mapping is not "fixed", it has many parameters that the user can fiddle with depending on the final look he wishes to get. And the standard view only mimics the default iray parameters that will mostly change. Unfortunately there's no easy way to convert the iray tone mapping parameters into the blender tone mapping parameters.

edit. note. As noted by William Hurst at bitbucket, tone mapping is usually done in post production. Both in daz studio and blender to avoid tone mapping it is possible to render to exr, that's hdri images without tone mapping. Then the tone mapping can be done in the post production application, as gimp or the blender compositor for example, or any application that can handle hdri images.

Converting Morphs to Shapekeys and Morph Presets

A morph in DAZ Studio is either a driven pose or a shapekey, or a combination of both. Driven poses are application-specific, so if you want to export morphs to a game engine you need to convert the driven poses to shapekeys first. This is done with the Convert Morph To Shapekey button in the Advanced Panel > Morphs panel. However, if your character has many morphs, it takes a very long time to convert them all. Let us estimate how long.

Each facial morph typically affects all faces bones, so the time needed to evaluate the final location of a face bone is proportional to the number of loaded morphs. Hence the time needed to evaluate a single morph grows linearly with the number of loaded morphs, and the time needed to evaluate all morphs grows quadratically. To reduce the conversion time, we can divide the morphs into manageable batches, which are loaded, converted and saved in temporary files. The conversion time will then be proportional to the total number of morphs times the batch size, which is much smaller if we keep the batch size down. When all files have been written, they can be loaded with the Import Custom Morphs tool and exported to the game engine.

The shapekeys are stored in morph preset files, which should be readable by DAZ Studio. Unfortunately, I have not yet managed to load the presets in DAZ Studio, but the files can be read by the Import Custom Morphs tool which is what we need for this application.

The tools that we are going to use are located in the Advanced Setup > Morphs Panel.

Load some morphs, e.g. the expressions. Press Convert Morphs To Shapekeys are select the morphs that you want to convert.

Here is the original angry morphs, using the driven face bones.

And here is the converted shapekey.

Morph presets are save as individual files, one for each shapekey, in the directory specified below the Save Morph Preset button.

In the popup dialog, we specify which shapekeys we want to save a morph presets. We can also change the directory, but here there is no folder button that opens a file selector.

The duf files are saved in the specified directory.

Once all batches have been converted and saved as morph presets, we reload all the shapekeys with the Import Custom Morphs button. Since we are going to export the shapekeys to a game engine afterwards, using rig property drivers is unnecessary.

Combo Materials

DAZ characters have many materials for the skin: face, torso, arms, legs, lips, nails etc. If we want to edit the materials once they have been imported into Blender we hence have to make the same changes in many places, which is inconvenient and error-prone. Until now, there have been two tools that facilitate editing multiple materials: the material editor and UDIM materials. However, both approaches have significant drawbacks.

The material editor has a clumsy interface, and is limited to changing existing parameters. It cannot change the topology of the node trees, e.g. by adding or removing nodes or editing links.

UDIM materials renames textures and saves them locally, and you must make sure that the UVs lie in the right tile (wrong for G81F arms and legs). Moreover, there is a problem with the bump distance, which depends on the pixel density and the mesh area covered by the texture in Iray. Hence the bump distance in Blender is different for the various skin materials. To keep the correct values, UDIM materials with different bump values must remain different, which defeats the purpose of editing all of them at once.

Some time ago Aszrael suggested a better approach: replace most of the node tree with a single node group, and only keep the textures. This node group is called a combo group and the materials that use it combo materials. We can then edit the combo group in a single place, and all combo materials are changed consistently.

To create a combo material, we use the Make Combo Material button at the bottom of the Material section. The active material is used as a blueprint for the combo group, so it is important that one of the skin materials is active.

The popup dialog lets us select the combo materials. By default the skin, lips and nails materials are selected. The active material is displayed at the bottom of the dialog.

Here is the original torso node tree.

And here is the node tree after most of the node tree has been replaced by the combo group. Apart from the output node, only the texture nodes remain, since they differ between the combo materials. The combo group is the same. Note that the combo group has a Bump:Distance input. This is the bump distance which differs between materials depending on the covered mesh area.

Here is the inside of the combo group. The input sockets are named after the nodes and sockets they are connected to, ignoring any math or mix-rgb nodes inbetween. The output sockets, called Cycles, Eevee, Volume and Displacement, are connected to the corresponding sockets of the output node.

Shell nodes are not included in the combo group. The reason is that a shell typically only affect some of the skin materials (usually the torso) and not the others.

Textures and texture-like nodes are left outside the combo group. Here we have a node group that corresponds to a layered image in DAZ Studio. In the other skin materials this node is a standard image texture node.

After converting to combo materials, the layered image node group stays outside the combo group.

It sometimes happens that some skin materials have extra nodes. E.g., the face and lips materials can have node groups that correspond to the diffuse overlay or makeup channels in DAZ Studio. In that case it is important to select the right active material to start from.

Here we have a character with eye makeup and glossy lipstick, and the result if we make combo materials starting from the torso, face and lips materials, respectively. The torso material doesn't have the overlay group, so the makeup is ignored altogether. The face material keeps the eye makeup, but the lips material doesn't have a lipstick texture so the color is replaced by black. Also the lips are glossier (have less roughness) than the rest of the skin. So when we start from the face, the lips lose gloss, and when we start from the lips, the rest of the skin becomes too glossy.

The solution is to make the combo materials with the face as the active material, and exclude the lips material from the conversion. The reason why the overlay group does not affect the other materials is that missing textures are replaced by pure black, cf. the lip color above. In the torso material, the Fac input of the diffuse overlay node is black i.e. zero, so the overlay node has no influence.

Combo materials are easier to use and more powerful than the old material editor. The latter is therefore deprecated and will probably be removed in the future, perhaps by the eventual release of version 1.6.2. The only drawback with making combo materials is that they are destructive; once converted to combo materials there is no going back. It can therefore be a good idea to backup the original materials, e.g. with the Make Palette tool.

Geometry Nodes and Geografts

In the previous post we discussed how to use geometry nodes to add geoshells to a mesh. This time we will use geometry nodes to merge geografts. The new option to the Merge Geograft button is available in the development version and Blender 3.1. Also this setup was explained to me by Midnight Arrow.

The advantage with geometry nodes is that they are non-destructive. Once we have joined the geograft with the body mesh destructively, the vertex order has changed and we can no longer add new morphs. There is an option to add a vertex table which keeps track of the original vertex numbers, but that only works for shapekeys which don't intersect with the geograft, and no morphs can be added to the geograft. If we merge with geometry nodes on the other hand, the original meshes are still present, and we can add new morphs if we disable the nodes modifier.

Here is the geograft we want to merge: a tail.

Select the body and the tail and press Merge Geografts. Enable the new option Geometry Nodes (Experimental). Also disable Add Vertex Table, which is unnecessary since geometry nodes keep the original meshes intact.

The geograft is still present but it is hidden, both in the viewport and for rendering.

The body mesh acquires a new nodes modifier. It takes three inputs: the edge vertex group which specifies the vertices to merge, the mask vertex group which contains the vertices to delete, and the merge distance. The latter is set to 0.1 mm which should work in most cases. The distance should be decreased if there are vertices closer than that.

Here are the edge and mask vertex groups.

And here is the node tree.

Here is the tail geograft, before and after it has been merged to the body.

To add a new shapekey, disable the nodes modifier in the viewport and unhide the geograft mesh. We can now add morphs and other shapekeys as usual. Once the morphs have been loaded, the modifier is enabled again.

Here we added a shapekey to the tail in this way.

Merging with geometry nodes is rather expensive. We can speed up viewport performance by disabling the nodes modifier while we build poses, and reenble it when it is time to render.

If we want to merge the geograft destructively, e.g. because we want to export the character to some other application, we can simply apply the nodes modifier. Unfortunately this only works if the mesh does not have any shapekeys.

Geometry Nodes and Shells

Geometry nodes is a powerful way to manipulate meshes that was introduced in Blender 3.1. They are used in the development version of the DAZ Importer as an alternative way to import geoshells and geografts from DAZ Studio. This could not have happened without the help of commenter Midnight Arrow, who explained to me about geometry nodes in general, and how they could be used in these specific cases.

This blog post describes how to import a geoshell as a geometry node setup in Blender. Later posts will cover geografts and how to import characters with shells and geografts directly from the DAZ database, without taking the detour over DAZ Studio.

Here we have a dirty character in DAZ Studio. The dirt is added with a geoshell called FX layer 01.

In the Parameters tab we find that the shell is pushed away from the main mesh by a small distance; Offset Distance = 0.0050 cm. There is also the list of surfaces affected by the shell.

By default a shell in DAZ Studio corresponds to a node group in the Blender materials. To generate a geometry node tree instead, we change the global setting Shell Method to Geometry Nodes (Experimental).

The body mesh looks strange in the viewport. This is because the shell becomes a second mesh which is located in almost the same place as the body mesh.

The shell by itself is an empty mesh, i.e. it does not have any vertices, edges or faces. But it has materials and a nodes modifier which generates the mesh. The modifer has a number of parameters:

• Figure: The mesh that the shell copies.
• Shell Offset: This is the Offset Distance parameter in DAZ Studio. In this case it is 0.005 cm = 0.00005 m.
• Material slots: There is an entry for each material where the shell is visible and not totally transparent.
  

We can inspect the node tree in the geometry node editor. The nodes modifier generates a new mesh where the body materials are replaced by the shell materials.

Here is the shell mesh by itself, with viewport shading set to sold and rendered, respectively.

Here is a rendered example, with the two different Shell Method settings.

 

There is a problem with previewing the shell materials. Geometry nodes require that the materials pick up the UV maps with named UV Set or Attribute nodes, but Blender 's previewer only works if we use a Texture Coordinate node for that.

Here is how one of the shell materials is previewed. Since it uses a Attribute node, the previewer doesn't find the UV coordinates but uses the value of the first pixel at (0,0).

Fortunately, we can use the new Make Palette tool to preview the shell materials. This tool was originally intended for storing materials for the new asset browser, but it can also be used for previewing. Select the shell in the outliner and make a palette.

Here is the palette viewed from above, in solid and rendered viewport shading. The shell mesh has nine materials, but there are only eight material slots in the nodes modifier. This is because the Irises material (material number 8) is visible but purely transparent.

Softbody Simulations

 

In real life body fat tends to have motion of its own - female breasts bounce, the belly and posterior of a fat persion jiggles, etc. - and that is best handled by softbody simulations. In DAZ Studio we have dForce, but simulations are not easy to transfer between applications. Moreover, dForce is a cloth simulator without pressure, and thus it can’t do softbodies properly. This is evident when the dForce “softbody“ collides with a prop, it doesn’t preserve the volume. At its best dForce can do bouncings, but not softbody collisions as Blender's softbody simulator can.

The DAZ Importer now has a new tool that adds a softbody simulation to Genesis characters directly in Blender. The setup was suggested by Alessandro Padovani in this thread, using ideas by Aneesh Arts explained in https://www.youtube.com/watch?v=eggOO9CIyp4. The Blender manual for softbody animations can be found at https://docs.blender.org/manual/en/3.0/physics/soft_body/index.html.

It should be stated from the outset that I am not an expert in simulations. The softbody simulation created by this tool works quite well in most cases, provided that the animation is believable. However, if the softbody object is subject to excessive force, either due to acceleration or to collsions, the softbody objects may collapse, giving the impression of a broken breast implant. Probably not the effect you were looking for. In such cases you either have to tweak the simulation parameters or modify the animation. But in most cases the softbody simulation does work and gives plausible results.

This is work in progress and available only in the development version of the DAZ Importer. It is not part of stable version 1.6.1.

The tool that adds a softbody simulation is called Add Softbody and is located at the top of the Finishing section. It is very important that the softbody simulation is added before the main body mesh is modified in any way, e.g. by merging geografts or eyelashes to it. Therefore the button is located before the merging tools.

Easy Import also has an option to add softbody simulations.

Three kinds of softbody objects can be added; chest, belly and glutes. You probably want all three kinds to simulate an obese person with much body fat everywhere, whereas for a slender woman the chest option may suffice. There is also an option to combine all there softbodies into a single object. Keeping multiple softbody objects makes it possible to tweak the simulation parameters independently, but adds to the complexity.

Collision objects for arms and legs can be added. If you only add softbody for the chest you probably only want to add collision objects for the arms, since it is unlikely that the chest will collide with the legs.

Finally there are options to add a corrective smooth modifier to the meshes and to remove existing softbody objects.

A new collection called Simulation is added. It contains the collision and softbody objects. The collection is hidden, but we may unhide it in the viewport to tweak the simulation parameters.

When visible, the softbody objects are red and the collision objects are green in the viewport. If the simulation does not work as intended, the simulation parameters may be tweaked here. The video by Aneesh Arts explains the meaning of the simulation parameters well. The Blender documentation is also a valuable resource.

If you create a combined softbody objects, you can still assign different masses to the parts with the MASS vertex group

The simulation goal is the vertex group that is pinned during the simulation. By default the goal is the vertex group PIN. The tool defines another vertex group, PIN BRA, which may be a more suitable goal if the character wears a bra which prevents the bottom of the breasts from bouncing freely. You can of course also define your own vertex groups if your character is wearing clothes that keeps parts of the body fat in place.

The simulation is only using the softbody and collision objects. Since those have a low polygon count, the simulation is quite fast. The deformation of the meshes is done by surface deform modifers.

Note that the surface deform must be unbound before any changes to the mesh is done. The Merge Geografts and the new Merge Meshes tools are aware of that, and unbind any surface deform modifiers first and rebind them again once they have finished.