Grease pencil trick: draw on surfaces with consistent offset! (Blender 2.92)

0:00 intro
0:28 getting started
2:05 adding a holdout material
3:28 possible solutions and their problems
4:07 my solution!

SOCIAL MEDIA

Equipment
TO DRAW
Wacom cintiq (I was VERY lucky to buy one second hand!)
Wacom intuos pro medium
Blender 2.92

TO MAKE VIDEOS
OBS for screen recording
My webcam to film my face
Zoom H1 Handy recorder for audio
Blender 2.92 to edit
iPad and procreate for the thumbnails

Creators of the prints on my wall:

DO YOU LIKE READING INSTEAD OF LISTENING? Here's a transcript!

GETTING STARTED
Let’s start by opening up a new file and choosing 2D Animation. We have our grease pencil stroke object here, and we want to add a mesh to draw on top of. We can switch out of Draw mode into Object mode up here, then all we have to do is press Shift A, and for this example let’s go into Add Mesh and choose a UV sphere.
We won’t make any changes to our sphere, instead let’s select our grease pencil object and go into draw mode. Up here is where we can choose how our strokes will be placed - Origin and 3D cursor both result in drawing on flat planes, but if we select surface then we can draw on our sphere and the strokes will follow its shape. Really cool! I use this for most of what I do in 3D with grease pencil.
Now notice when you draw that there’s a gap between the strokes and the object. This is the offset. We can modify that here, with a larger number giving you a bigger gap. The problem that I’m going to be trying to solve in this video is that this offset isn’t consistent. If you draw while you’re very zoomed in, the gap will be much smaller, and if you draw while you’re very zoomed out it’ll be huge. I zoom in and out constantly while I’m drawing, so… this doesn’t work for me.
You can set the offset to 0, but then it’ll render really funny. Technically this isn’t a problem if you don’t plan on including the mesh in your final render, but I draw on all sides of my objects and if I hide the meshes from my final render then I get… this.

ADDING A HOLDOUT MATERIAL
I much prefer to keep my meshes and to give them a holdout material
Hey, really quick, probably would have been nice if I explained how to do this. So up here in the workspaces, I’m not sure if it’s already included in the 2D animation so in case it’s not, if you go into sculpting then you look for the shading workspace. So from there we’ll just click on our object that we want to change the material of, if it doesn’t have any material then we’ll add one. And then basically just select this big box, hit delete, and then you can press shift A and then in shader look for the holdout. And then just plug in the holdout to the surface.
So basically what this does is that it makes the object invisible so that it doesn’t show up in the final render, but it still hides the strokes on the other side so that you’re not seeing this mess.

POSSIBLE SOLUTIONS AND THEIR PROBLEMS
Maybe you’re thinking we make the offset 0 and then scale down our object. Fair, this will work in this example because it’s a sphere, and we haven’t touched it at all, edited, sculpted it at all, but as soon as you have any object more complex than a sphere, scaling it down… just flat out won’t work. Here’d kind of an example of what you’ll get. Also, what if you need to go back and change your drawing at all? Scale it back up and hope for the best? Not a fan of that idea.

MY SOLUTION
Instead, here’s my solution:
So let’s go back into Object mode and select our mesh object. We’re going to give it a solidify modifier. Before doing this I recommend pressing Ctrl A and choose Apply All transforms, because otherwise the modifier can act funky. So modifiers are found in this blue wrench icon, and the solidify modifier is… here. Here I set the offset to 1 and typically I keep the thickness around 0.01 to 0.04, you can play around with that, see how it works with your piece. Then we can click on this blue camera icon over here and turn it off. This means that we’ll see the modifier while we’re working with Blender, while we’re drawing on top of the object, but when we hit render the object won’t have this extra thickness.
This means, yes, we can now draw on this object with the offset set to 0, when we render it the strokes will all look perfect, they won’t be affected by the mesh at all, and they’ll all be at, like, almost exactly the same distance from the mesh no matter how zoomed in or out you were when you drew them. Like if you zoom out a crazy amount, yes there’s a small difference, but it’s nothing like what it was before. And overall they are just so much more consistent than if you were to use any value for the offset.

[SophieJantak]

Just a heads up that I won't be answering any questions or replying to comments on this video. It's really cool that it's still getting views, but I don't use grease pencil for drawing on 3D objects anymore, and so I really can't offer any more help or guidance!

[Bumpy-Man]

YES. Been following grease pencil's development for years to see this. I know this is niche stuff, but you're literally the first person I've seen talking about the issues & solutions involved in grease pencil ALL the way around a 3d mesh. Your work is inspiring, your message concise, and your delivery full of charm. THANK YOU! I am beyond excited to see more.

[ShiningDawn]

I'm currently working on a project with characters that have Grease Pencil stuff as part of their design along side the model and texture and all that.

My solution for this issue was to just hit numpad 5 on the keyboard to switch the camera from perspective to orthographic. Now the distance from the surface of the model would stay the same no matter how much I'd zoom in or out.

[NVD]

The way you use blender is impressive.

[MaigaVidal]

I feel like you’re talking a whole different language but it’s FASCINATING

[anotherKpresser]

It's probably been said somewhere else in the comments but here's
another possible solution: instead of a solidify you could use a
displacement modifier with a negative value. It works exactly the
opposite way (it pushes the faces inside along their normal) and of
course you'd have it disabled during the drawing phase and enabled in
rendering. The possible benefit (?) could be a slightly more responsive
experience (not having to compute the modifier at draw time) and the
ability to add the modifier a the end of the process to a bunch of
meshes (in theory you could also achieve the same result entirely in the material without the modifier if you render in cycles)
oh and just found this channel but I love the things I've seen so far

[cwgochris]

You have a very pleasant video personality. This is the perfect video for me, since I want to use Grease Pencil to make small animations and attach those animations to surfaces. Like making a GP animation of a moving mouth or cartoon eyeball and attaching the animation file to a modeled head shape. I think this video has shown me exactly what I was looking for!

Keep making videos!

[Zenzuke]

I love your videos and your personality, I hope your channel explodes in popularity.

[snofixart]

I've searching for this for days!
You're a life saver.
And keep them coming.

[DarrenJohnsonGraphics]

How someone manages to figure this stuff out is way beyond me, thank you for sharing, I really like your art too!

[SophieJantak]

TIMESTAMPS (because idk why the chapters aren't working...)
0:00 intro
0:28 getting started
2:05 adding a holdout material
3:28 possible solutions and their problems
4:07 my solution!

[jackjackalvarado]

I am SO impressed with the tips and tutorials you provide on your channel. Normally I have to really dig through different videos on various channels to find all of the information I need, but you share it all! Thanks so much!

[zzjapannevergiveup]

Actually, I have learnt many from this solution from her. I did not know that and now I’ve decided to learn and use for my project. Thank you so much.

[angelspeaks]

This is the best video ever. Just the right amount of instruction and show. Just subscribe

[ronaldbell]

At 01:39, I just want to say you're awesome. I was trying to learn grease pencil today, and I was getting really frustrated because I couldn't get the curves to lie against the surface I thought I was drawing on. I totally missed that little slider, and the tutorial I was following didn't mention it either. I looked everywhere in blender settings except the right spot. Thanks!

[macrumpton]

This is really great content. You could do a whole series for traditional media artists and 2d digital artists about how Blender can open up a new world for them! A couple of decades ago I had a project taking the paintings by an artist friend and wrapping them around shapes to create painted environments (in quicktime VR) so you could go inside and travel through them. Sadly the tech was not up to the task, but we still talk about that project. Maybe it is time to try again...

[wilsonstreet]

ever since i found out about greasepencil before i even officially picked up blender ive been obsessed with its concept and seeing it be used alongside 3d in such a freeform way is making me maybe the most inspired ive ever been regarding 3d art.
Also, DON'T STARVE <33 that was a beautiful tallbird that showed up for like a maximum of 4 seconds LOL.

[MelvilleG]

You are a beautiful human being. And you have an amazingly soothing voice. May luck and millions of subscribers be with your channel.

[filipemecenas]

Your are the best teacher of Grease pencil ! ❤️Thanks alot !

[kentjensen]

Not only are you talented and expert, and not only are you great at teaching (even with the inserted bit hehe), but I don't think I'veever seen anyone this relaxed and natural on cam here on YouTube. I hope in 2021 your channel grows from 111 subscribers to 111, 000 subscribers. I'll start you off by becoming subscriber number 112 right now.