Posted on April 27, 2021, 12:44 p.m. by ciribestgirl • Last updated on June 30, 2021, 11:15 a.m.
This was a guide I wrote a while ago with assistance from @doublenyl on how to attach his rigged Urgarulga Hotdog (futa appendage) to female meshes.
Intermediate level Blender skills are required.
If you are a beginner, do not attempt to do this tutorial until you gather more experience as some details are assumed: knowledge on modelling and basic rigging + weight painting is essential. Work through Crute's beginner list first. Please do your own research when unsure about anything and do not bother the Smutbase blender discord channel unless absolutely necessary.
EDIT: Dreamrider workflow videos included as an example. Also revised to simplify some steps thanks to Dreamrider and crute.
Nyl's hotdog is too high resolution and without decimating the poly count the merge step will be extremely tedious. Unfortunately the mesh can't be unsubdivided with a multires modifier. One way is to manually dissolve edge loops as Dreamrider has done here:
Another alternative is to export it into Maya and run mesh reduce.
"With my models I completely sew the two meshes together, I don't use any boolean modifiers. I join the meshes and armatures, merge the vertices together, and then clean up the textures and weight paints. It's an involved process.” - Nyl
Simply do as above. In detail:
At this point you should do some book keeping: go into weight paint mode and check that none of the weights are messed up, and in pose mode check that the character poses normally as before and that the hotdog follows the pelvis/hip as expected.
You may also notice that the shaft hood and hotdog skin forward bones on the hotdog no longer work after merging. These bones previously controlled the shaft forward and foreskin forward shapekeys in the hotdog and need to be relinked. Look up drivers and how to link shapekeys to bones to get these working again.
Before starting the weld, make sure to create a new shapekey as a backup, in case something goes wrong, and also save a copy of the file.
In edit mode:
Now delete the faces that cover the region of the welded vertices (i.e. create a hole underneath the hotdog base).
Now that everything is merged, the weights around the pelvis and hotdog base regions need to be fixed, since we created a hole this step is unavoidable. Weight painting is a large topic so won’t be covered here; in a nutshell, you need to find which bones in the female armature previously influenced the deleted vertices and fix/repaint the areas around the hotdog. Usually the culprits are the hip, pelvis, lower/upper abdomen, upper thigh bones, but every model is different. Check the weights of the Wonderwoman model and try to mimic it as best you can. Roughly the parent bone weights, either the hip or pelvis, should look something like:
At this point your hotdog still won’t look as good as the Wonderwoman model because of anatomy. There are two main muscles surrounding main hotdog shaft (crus of the outer shaft muscle):
These become very prominent when a hotdog is erect. This is modelled into the Wonderwoman model as a shapekey:
You can mimic this appearance in your merged hotdog model, which will greatly add to its realism. The easiest way is to create a shapekey in your futa mesh, and then in the shapekey create the muscle ridge in sculpt mode using a combination of move and add brushes. Since this step can easily be done on your own, will not go into further details, just watch some tutorials on YouTube if you are not familiar with blender sculpting tools and/or shapekeys.
“I just use the clone brush in texture paint mode, I don't redo any of the UV's. I'll usually do a pass at full strength, then start smoothing things out by reducing the strength with each pass. Repeat the same process for all textures involved (diffuse, specular, normal, bump, etc.)” - Nyl
If you haven’t already, open up an image editing program of your choice, e.g. photoshop and try to match as close as possible the diffuse colour of the hotdog model to the female model. This will provide a good starting point for blending the textures around the seam area.
Now switch to texture paint mode (make sure you are in solid viewport shading, as the textures will not update itself in the viewport in material preview and rendered modes) and select the clone stamp tool. Note: from experience it usually looks better cloning from the hotdog textures to the female mesh textures.
For diffuse textures you don’t need to do anything extra, you can just start cloning straight away: ctrl-click on the hotdog or pelvis boundaries (depending on the direction of cloning you want to do) to clone that area, then click to apply the clone on the seams. Do a pass at 100%, then repeat at progressively lower clone brush strengths, e.g. 50%, then 25%, 10%, etc. This will help it blend more seamlessly.
Now repeat the exact same procedure for all the texture maps, normals, specular, etc. Select the appropriate texture to paint in texture mode (e.g. if I want to paint the normal map, I will just select the normal map texture in the material slot for the hotdog and the torso, then start cloning as before).
Create a new BSDF node and add a mask texture that blends from the hotdog material to the torso material. This helps hide the specular/shininess difference on the seams even better due to using two different shaders for the torso and hotdog.
See Dreamrider's example here: https://discord.com/channels/202174190558642177/360718065626775555/850856049900388362
Afterwards that’s it! Start doing some test renders and animations to see if everything works correctly! Usually, you may need to go back to weight painting from time to time or some of the other steps to fix some issues as you find them.