sculpt a tank in vr

Dis­cover Ocu­lus Medium’s new pre­ci­sion tools with this two-part tu­to­rial from Martin Ne­be­long

3D World - - CONTENTS - Martin ne­be­long Martin is a free­lance artist liv­ing in Den­mark. He has been work­ing as a 2D artist for 15 years, but since he got his VR head­set, 3D is be­com­ing an in­creas­ingly big­ger part of his work. www.art­sta­tion.com/mar­tin­ity

Fol­low Martin Ne­be­long’s step-by-step process to cre­at­ing hard-sur­face mod­els in VR with Medium

Since I tried Ocu­lus Medium for the first time al­most two years ago, one of my only con­cerns with the pro­gram was the lack of grids, guides and snap­ping tools. Ba­si­cally, the lack of these tools meant that any time you wanted to make a build­ing, a robot or any other hard-sur­face model, you’d have no choice but to sim­ply eye­ball the re­quired an­gles. You could still get de­cent or even great re­sults by work­ing this way, but it took way too long com­pared to the time it would take oth­er­wise. Now, fi­nally, those tools are here with the re­cent re­lease of Medium 2.0.

In this tu­to­rial, which is part one of two, I’ll take you through the process of cre­at­ing a hard-sur­face model in Medium 2.0, util­is­ing these new pre­ci­sion tools. I’ll be sculpt­ing a made-up tank, us­ing var­i­ous ref­er­ences found on­line. We’ll also take a short trip into Quill to make the tank tracks. Here I’ll in­tro­duce how you can draw very pre­cise shapes in Quill, and how you can then take your Quill scene and use it in Ocu­lus Medium.

The tank sculpt it­self took around an hour and 15 min­utes, and ev­ery one of those min­utes felt like play­ing a game. That’s one of the things I love about sculpt­ing in vir­tual re­al­ity – it’s just pure fun.

Af­ter read­ing through this tu­to­rial, you should be ready to ex­plore the world of VR hard­sur­face mod­el­ling to be­gin mak­ing your own cre­ations!

01 Find ref­er­ences

I de­cided early on to do a tank, be­cause it just fits the hard­sur­face cat­e­gory re­ally well and fea­tures lots of de­tails. Since I’ll be freestyling this one, I won’t need spe­cific tank ref­er­ences and can pick and choose what I like. I find ref­er­ences and keep them on my sec­ondary mon­i­tor off to the side of my workspace.

02 Quick visit to Quill

For the tank tracks, I de­cide to do a quick Quill draw­ing and use that in Medium, where I can turn the Quill draw­ing into sculpt­able clay.

Quill is amaz­ing for quick, re­peated de­tails. You can now con­strain lines to x/y/z by choos­ing the line tool and hold­ing down the off-hand trig­ger, while draw­ing the line in the gen­eral di­rec­tion you want it. A sim­ple draw­ing like the one in the ex­am­ple would have been dif­fi­cult to do in the previous ver­sion of Quill.

An im­por­tant note when you’re draw­ing in Quill with the aim of ex­port­ing to Medium is to draw with ‘wa­ter­tight’ shapes, since Medium will oth­er­wise have a hard time con­vert­ing the ge­om­e­try from Quill into vox­els. So use any­thing but the rib­bon brushes and the line brush and you should be good. Even with wa­ter­tight meshes though, Medium might still have trou­ble con­vert­ing very com­plex scenes.

03 change an­gle OF con­strained lines

Once you’ve drawn a line, se­lect it with the se­lec­tion tool (press X) on your con­troller, and make sure you’ve set the trans­form gizmo to show (press in on your left thumb­stick if it doesn’t). Now you can snap-ro­tate the item while hold­ing down the right trig­ger and drag­ging on the gizmo ‘rings’. This will con­strain the item to 15-inch in­cre­ments, giv­ing you more pre­cise an­gles to choose from. You can also ro­tate freely on any of the three axes by pulling on the gizmo with the right thumb but­ton pressed.

The best way to get com­fort­able with this tech­nique is to draw ran­dom shapes and drag them around with the gizmo, ro­tat­ing them in in­cre­ments, mov­ing the pivot point around and so on.

04 cre­ate Ba­sic shape OF First tank track link

Us­ing that tech­nique, we’re able to quickly form the first part of the tank track. Since there’s no ‘live’ sup­port for symmetry draw­ing in Quill, I find it eas­ier to copy the line or shape I want to mir­ror, and just flip it us­ing the an­gle-con­strained ro­tate gizmo (hold right trig­ger while drag­ging).

The red box is ac­tu­ally me ‘hack­ing’ the sys­tem by draw­ing in Boolean shapes on a new layer in Quill. So the red box will ac­tu­ally be sub­tracted from the tread in Medium, which is able to im­port the sep­a­rate lay­ers from Quill. To switch be­tween lay­ers, you can tog­gle an op­tion to jump to the layer of the first ob­ject you se­lect, un­der the se­lec­tion tool in the tool menu.

05 Make a wheel in Quill

Let’s make the tank wheels so that we can shape the tank tracks around that. To cre­ate a wheel in Quill, make a sin­gle hor­i­zon­tal line. Se­lect that, and move its pivot point by hold­ing down the thumb but­ton on your main hand while drag­ging on the ver­ti­cal gizmo line. Drag the pivot down far enough to reach the imag­ined cen­tre of what will be the outer shape of the wheel.

Now drag the line around the off­set pivot point by drag­ging on the ro­tate gizmo with the right thumb but­ton held down, while you also hold down your left trig­ger to make a copy.

Once we have a com­pleted cir­cle, we can give the wheel depth by se­lect­ing the cir­cle and mov­ing it us­ing the trans­form gizmo while hold­ing down the left trig­ger to make a copy. Once you’ve moved

it down far enough, just push your off-hand thumb­stick right to re­peat trans­form and copy. When you’re happy about the outer shape, you can then use the square brush, com­bined with move/copy ac­tions, to fill the in­side of the wheel.

06 cre­ate small wheels

Now that you’ve seen how to make a ba­sic wheel, it’s time to make the first tank wheel. I do this us­ing the same tech­nique and add small riv­ets to the in­side of the wheel to up the de­tail level.

Now it’s time to copy the wheel and make smaller ver­sions for the lower part of the tank tracks. To make a smaller copy, se­lect the whole wheel and hold down on one of the axes with the right thumb but­ton. While do­ing so, push up or down on the right thumb­stick.

Once I have the scale I need for the smaller wheel, I move it into place next to the large wheel. Then I make a copy of that wheel and drag it slightly to the left. I re­peat the trans­form and copy ac­tion by push­ing right on my off-hand thumb­stick un­til I have the num­ber of wheels I need. Us­ing the line tool and the cylin­der brush, make small me­chan­i­cal con­nec­tions be­tween the wheels.

07 add the tank tracks

Now that the wheels are in place, it’s time to make the tank tracks that go around them. Make a se­lec­tion of the first tread we made, and copy that us­ing the tech­nique we used be­fore for mov­ing and ro­tat­ing us­ing the trans­form gizmo. In ar­eas such as the bot­tom and top part of the tread where we have lots of hor­i­zon­tal re­peats, use the left thumb­stick to re­peat trans­form and copy.

08 ex­port tank tracks

Ex­port as FBX, and turn off Ex­port Curves, Ex­port An­i­ma­tions and Ex­port Hid­den. Ex­port­ing as FBX will re­tain all lay­ers in the file, whereas OBJ ex­ports will save ev­ery­thing in one layer.

09 im­port the tracks to Medium

Fire up Medium. Go to File and se­lect Add Mesh as Clay. Now you’re pre­sented with a wire­frame ver­sion of your mesh. There’s a bound­ing box around the ob­ject that rep­re­sents the layer bounds. The closer you scale this box to your mesh, the higher the voxel den­sity will be, and the longer the con­ver­sion will take. I usu­ally set this to around 80% or so which seems to work fine most of the time. Also check the Split Mesh Into Sep­a­rate Lay­ers box. If your im­ported mesh is very large, ei­ther scale it down if it’s one layer, or scale the Ex­port Trans­form ob­ject up. That will al­low you to zoom fur­ther out.

10 sub­tract

Next up we want to sub­tract our sub­trac­tive Quill layer from the mesh. We do this by open­ing the scene graph. Then we point at the layer we want to sub­tract from and click to se­lect it. Next up, point at the layer you want to sub­tract and click while hold­ing down the left trig­ger to se­lect that as well.

Medium then knows that the last clicked item is to be the sub­trac­tive layer. Next, hit the Sub­tract but­ton.

11 Mir­ror

Now that we have one set of wheels and tank tracks ready, we need to mir­ror that. So go to the scene graph, se­lect the tank tracks and wheels (point with the laser pointer, click to se­lect, hold down left trig­ger while click­ing to se­lect mul­ti­ple items), hit Du­pli­cate and then Mir­ror. Some­times your mir­rored items don’t ap­pear where you ex­pect them to. If this is the case, the ob­ject you’re try­ing to mir­ror is not off­set cor­rectly in re­la­tion to the mir­ror. One so­lu­tion to try is to make sure the mir­ror is vis­i­ble and then un­der its Trans­form set­tings, re­set ev­ery­thing to zero or move items man­u­ally.

12 sculpt the Hull

Us­ing the tank tracks and wheels as a guide, sculpt the hull of the tank. For this I use a square brush set to line, with ta­per turned off and con­tin­u­ous dis­tri­bu­tion. I en­able Grid Snap, and find a fit­ting size for the grid. First I keep An­gle Snap at 90, and when I have the over­all vol­ume in place I sculpt into that with lower An­gle Snap set­tings, or even with an­gle snap­ping off. To quickly switch be­tween adding or

sub­tract­ing, dou­ble tap A on your main hand.

If you find that your mesh looks too ‘soft’, in­crease the layer res­o­lu­tion by click­ing the layer in the scene graph and press­ing In­crease Res. Be care­ful with this func­tion though, and don’t go over­board. If you were to fill a layer’s bound­ing box with high de­tails you’d very quickly hit a per­for­mance block. So if a large part of your layer doesn’t need de­tail, but a small part does, con­sider break­ing it up into a lowres layer and a high-res layer. It’s also worth re­mem­ber­ing that parts hid­den be­hind other el­e­ments still eat up per­for­mance, so if you have very dense meshes hid­den from sight, con­sider eras­ing those parts.

13 ar­moured skirts

The next step is to add the ar­moured skirts of the tank. Make a new layer, and make sure the res­o­lu­tion is high enough. You can in­crease layer res­o­lu­tion be­fore you even start sculpt­ing. When you do so, you’ll see a black sphere guide get­ting smaller and smaller. The smaller this is, the higher your mesh den­sity. One of the most im­por­tant things in Medium, in my opin­ion, is a good un­der­stand­ing of how res­o­lu­tion in Medium works, what it does for brush sizes, per­for­mance, ex­port size and the like. Gen­er­ally though, per­for­mance in Medium is great if you have a po­tent rig. I have a 1080Ti and have worked on very large and de­tailed scenes with­out any hic­cups. For the ar­moured skirts, start out with a large box over the tank tracks. Then us­ing the line tool, grid guide and An­gle Snap, I re­move most of that box and ‘carve’ out the cover. For the an­gled parts, I do the same and ‘carve’ out a plane sim­i­lar to the one on top. Then I go into the scene graph, click the lit­tle trans­form gizmo sym­bol above the layer name, and ro­tate the plane us­ing the ro­ta­tion gizmo.

14 add de­tails us­ing pre­fabs

Add a new layer and up the res­o­lu­tion. Then go into the tool set­tings and open the Me­chan­i­cal cat­e­gory. Find some fit­ting stamps, and again us­ing grid and an­gle con­straints with ta­per and con­tin­u­ous off, start plac­ing de­tails on top. All stamps can be used for sub­trac­tion too, so you can quite eas­ily change the ap­pear­ance of the ba­sic stamps if you want a more unique look. While I sculpt in the de­tails, I have a browser win­dow open off to the side, us­ing Ocu­lus Home’s ‘Vir­tual Screen’ func­tion. In the browser I search for a tank ref­er­ence and loosely base my sculpt on that.

15 sculpt the tur­ret

I add an­other layer, and sculpt in the over­all vol­ume of the tur­ret. For this ini­tial block­ing out, I usu­ally go with the square stamp. I love how you can do both hard and soft edges with this tool, de­pend­ing on how you an­gle the stamp. I keep the line mode ac­ti­vated and can quickly cut away, or add shape. As I start to see the form emerge, I choose smaller stamp sizes, and re­fine the sculpt us­ing those. While I sculpt, I con­stantly ro­tate the model and zoom in and out to make sure the form reads well from all an­gles. I also now and then ro­tate the lights to see how it af­fects the shape.

16 re­fine the tur­ret

We’ll add de­tail to the tur­ret in ex­actly the same way we did with the body of the tank. You can make your own hard-sur­face stamps if you like, but for this piece I go with the ones that come with the pro­gram. At the time of writ­ing this tu­to­rial, there is a bug in Medium when you use the Make Stamp func­tion that off­sets the stamp slightly, which

makes the func­tion bro­ken for stuff like this. What you can do in­stead is make a new file, make your stamp us­ing grids and an­gle con­straints, ex­port and then reim­port us­ing the Im­port Stamp func­tion. A bit of a has­sle but it works.

17 Make the can­non

Time for the can­non. I make the bar­rel of the tank us­ing the cylin­der brush com­bined with the line tool. I cap off the end of the can­non us­ing the square brush and make the bar­rel hol­low us­ing the cylin­der brush again. When sculpt­ing a model like this, I try to plan ahead for an­i­ma­tion, or at least make sure I could ro­tate the tur­ret and the gun. And now that Medium sup­ports up to 100 lay­ers, you don’t have to worry too much about hit­ting the limit. I add a small piece of fab­ric-like ma­te­rial at the in­ter­sec­tion be­tween the bar­rel and the tank tower.

18 add rail­ings

I want to add some small rail­ings to the top of the tur­ret, to make sure there’s some­thing to grab onto when en­ter­ing the tank. To do this we use the cylin­der stamp set to line mode, no ta­per­ing and con­tin­u­ous mode. An­gle snap­ping should be set to 90. Make sure your de­tail layer has enough res­o­lu­tion and draw a small line along the length of the tur­ret. Then, us­ing the Move tool with an in­ner ra­dius of 0 and strength set to 100, we can shape the rail­ing. I use a very large Move tool size for this, to get a more rounded shape on the rail­ing. Once I have the form in place, I add small lines that con­nect the rail­ing with the tur­ret.

19 ground plane

The work on the tank is now fin­ished, so I add a new layer and sculpt a ba­sic en­vi­ron­ment around the tank. For this I use a com­bi­na­tion of rock brushes. I work at a rel­a­tively low res­o­lu­tion here, and add a new layer with some ‘hero’ rocks with higher res­o­lu­tion. When you’re mak­ing en­vi­ron­ments like this, the Move tool with an In­ner Ra­dius of 90 or so works re­ally well, for quickly drag­ging out a ground plane for ex­am­ple. Just re­mem­ber to watch your layer res­o­lu­tion, as large en­vi­ron­ments get very per­for­mance-heavy if you have the layer set to high res­o­lu­tion. For very large en­vi­ron­ment pieces, you can sculpt a part of it, and then with the layer se­lected in the scene graph, scale the layer up in size.

17 20 tank track Marks

To have some track marks be­hind the tank, I du­pli­cate the tank track layer two times and place the tracks be­hind the tank in a mean­ing­ful man­ner. Then I sub­tract those lay­ers from the ground plane and voila!

21 ex­port

Now that we’ve come to the end of the first part of this tu­to­rial, it’s time to ex­port the model. Be­fore you ex­port as FBX (which re­tains both lay­ers and ver­tex colour), go through the lay­ers and check if any of them could be lower res­o­lu­tion, if there’s parts of lay­ers that you don’t need and can erase. And maybe, if you’re a bit more or­gan­ised than me, give the lay­ers proper names.

Af­ter a few hours of sculpt­ing and paint­ing in Medium and Quill, I now have a very solid model for the next tu­to­rial. There I’ll be tak­ing the model into Zbrush to op­ti­mise it by dec­i­ma­tion. Then I un­wrap each part of the model us­ing Ri­zomuv (for­merly Un­fold3d) and tex­ture it in Sub­stance Painter. I’ll also be talk­ing about dif­fer­ent ren­der­ing op­tions, both real time and ray­trac­ers.

As al­ways don’t hes­i­tate to con­tact me if you have any ques­tions about the work­flow. •

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