How to build for rthro?


Hi all,

I’m attempting to build a rthro character. The upright creature in the sketch is more or less what I’m aiming for (with a more Roblox-ish look). The other is a study to get familiar with the subject.

I’ve started the 3D model, but I’m flying a bit blind. I can’t seem to find much info on how to build for rthro.

  • Is there a guide for this stuff, or do I just look at an existing rthro model and figure it out from there? Any pitfalls to be aware of?

  • Does the geometry have to be built in any special way to support scaling?

  • I read that some existing Roblox models are in the ballpark of 1600 verts and use a single 1024 sq texture map. For any of you building for rthro, is that the target you are using?

  • Any other suggestions/tips/things to keep in mind/etc?

  • This isn’t an rthro question, but for a creature-character like the one in the sketch, would I be required to give it clothes?

I’ll start with that. Basically, I want to build for rthro and can’t find any direction beyond a smattering of comments here and there. Is it primarily trial and error at this point? That’s fine if it is; I just don’t want to assume that and then find an authoritative guide or a tutorial after spending hours trying to work things out.

Thanks for your time.


Rthro vs non-Rthro is not really relevant to your character, since the proportions aren’t even close to any existing R15 type. Tagging parts with one of the Rthro scaling types only affects their base scale, it’s a way of indicating what proportions the figure was intended to be compatible with, for the purpose of scaling the parts relative to other Rthro or non-Rthro body parts you might swap out. There is no difference in how you model or rig it, Rthro use R15 rigs.

You are not required to put clothing on an iguana. :joy:


LOL. *whew*

Thanks for your reply. It sounds like I was on the wrong track. This particular character is incidental. I’m learning about the new versions of MyPaint and Blender (2.8) and decided to design/build something for rthro as a motivation (also something I want to learn). I’ve had some luck twisting the R15 rig into something that could be used for many types of creatures, but what I’m trying to sort out are the criteria that separate a custom R15 creation from a valid rthro character. All of it may be obvious once I’ve managed to make one of these, but from this side it’s all a bit murky. That may be due to the limitations being much more severe than I imagined.

This sounds critically important. Let me see if I can unpack all the implications. So, there are slender and regular versions of the rthro rig. I assume these are the scaling types. The difference is in how the proportions change as a character is scaled… Ah. The full size rig/model isn’t being morphed/scaled to different proportions in a general sense, it’s transitioning from a taller version of the R15 rig to a normal R15 using one of the two scaling types. Characters must be built so they can use a (potentially) scaled but otherwise unmodified R15 rig. Is that about right? If the joint locations are moved will it break the rthro or is that something to test case-by-case? [nm. have been working with custom rigs and need to reset my thinking as to how all this works. Mesh geom attaches to default rigs. Nice and easy.]

So, what’s the typical build process look like? Do you import one of the default models into Blender and just build new meshes in the same locations as the old ones? Modify the existing meshes?


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I don’t know what other people do, but I make R15s in Blender by just modeling the parts and rigging them with a 15-bone skeleton. Then I import the parts into Studio, and manually translate the Bones’ “Head” joint world-space locations into the corresponding RigAttachment locations.

The Rthro scaling tags determine how the BodyProportionScale and BodyTypeScale values work. If you tag a character’s parts as Rthro, they will be at their authorized size when the BodyTypeScale is 1, and will scale down to blocky R15 shape when you slide it to 0. Otherwise they will be at authorized size when it’s 0 and will be stretched up to Rhtro shape when BodyTypeScale moves towards 1. BodyProportionScale works similarly–it lerps between narrow and wide Rthro–but it multiplies by the BodyTypeScale so if a character has BodyTypeScale of 0 it has no effect (because the character is fully non-Rthro).


Thanks for sharing your process and for explaining the scaling tags.
I noticed that the page for importing avatars also has some info about building them.

Going to leave the thread open since I’m bound to have more questions before I’m done.

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So, it is possible to move the joints around in Blender and still import (using the new avatar importer) as regular R15 rthro. The proportional scaling works as expected too. I assume the problem would come when trying to swap parts with other R15/rthro models.

The bones were giving me a headache, so I went with empties for testing. Will work out how to do this with bones when I get around to animating in Blender.

600 cm looks like a good height to build in Blender for a normal sized rthro and export fbx at 0.01 scale.

I was thinking the model needed to fit a standard R15 at the time I drew this. Will try something simple from scratch.

I’ll try to keep good notes and maybe put everything in some sort of end-to-end guide for other Roblox character making noobs like me.


Blender 2.8 Add Ref Images
Blender 2.8 Low Poly Animals Tut Pt 1
Blender 2.8 Low Poly Animals Tut Pt 2
Blender 2.79 Low Poly Hands

Blender 2.8 is pretty nice if you haven’t switched. My current workflow looks a lot like the animal tutorials above. I’m using mirror modifiers and subdivision surface modifiers. I got sidetracked trying a few different things for hands (like skin modifier and metaballs), but I think I’ll just go with something like the hand tutorial above. I need to spend more time designing places where the different geometry pieces meet. Looking at the model in the post above, it’s really only the elbows that are exposed, and just barely. I was going to try the cloth simulator in Blender for this test to see what was possible, so I wasn’t too worried, but it’s already clear that those joints shouldn’t be an afterthought.

Cloth, textures, and then I’ll parent everything to empties and export. I’ll apply attachments in Roblox (prob copied from a dummy model) rather than trying to set all that up in Blender.

Feel free to share your process if it looks like I’m overlooking something critical. Ideally, I’ll have a basic process to share (80/20) that covers essentials and tips from sketch through modeling/texturing and into Roblox (as Rthro and/or custom or whatever that breakdown looks when I get there).


since it’s an animal, I don’t really see anything wrong with it not having clothes

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Going with a bandit-peasant look for this test donkey-rabbit-whatever creature. I got sidetracked with the holidays and learning to make clothes with the cloth system, so progress slowed a bit. Having entirely too much fun playing with Blender 2.8.


  • finish modeling
  • retopo
  • texture
  • rig/hierarchy/correct naming/etc
  • export
  • import to Studio
  • add attachments
  • animate

I should probably rig, export, and test the geometry before I texture.
Still trying to work out the procedural differences between building for a custom char vs. standard Rthro. I probably just need to try a bunch of things and see what breaks and what works.

If you build characters that are interchangeable with other standard Rthro models, and you have a process/setup that ensures compatibility in all the relevant ways that you’re willing to share, I’d love to hear about it. Is the ability to swap parts of one Rthro model for another an important feature? I assume so. Exporting an R15 rig and having it scale using the scaling tags is all making sense to me. I’m not far enough along to know exactly how I need to constrain the modeling/rigging process to ensure that parts are interchangeable. Do I need to import one of the standard Rthro rigs from the Studio plugin into Blender and build to that, or is the system more flexible than that?


So, it doesn’t appear that the geom needs to be built in any special way to support R15/Rthro scaling, but characters do need to be built to fit R15, slender, or standard Rthro rigs unless you want to create custom animations for everything. I guess that’s what separates Rthro from Custom in a practical sense. This rabbit-archer character looks a little funny with the default running and jumping anims because I didn’t fit it to the Rthro rig exactly. It scales fine though.

Having a Blender starter file with all the standard joint placements for a char already mapped out may be a good way to begin a build. One could build with those joint positions as a guide and attach geom to the rig when ready to export.

Anyway, I think I have a viable process for all this now. I’ll come up with a simpler character and write out the steps for everything in case someone else needs help working through this stuff for the first time. Just realized that the normal Anthro character (Rig Builder) is 5600 tri and mine is 1800, so I have room to add geom detail.