[WIP] RECREATING A SKELL MECHA (XENOBLADE CHRONICLES X) - MASTERS
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SKELLS
This is a copy across from my university's work forums. I've been spending a couple of months on a hard surface vehicle/mecha project, due to conclude its development cycle in May.
I'm a 3D Modeller with experience on producing hard surface mechs for set timeframes. An it
My intended goal is to produce a mecha which fits into the design and construction blueprint of the Skells from Xenoblade Chronicles X (MonolithSoft & Nintendo).
Briefly, Skells are Pilotable Combat Mecha from MonolithSoft's Xenoblade Chronicles X (Wii U 2015). They're designed by Takayuki Yanase – Mecha Designer and Illustrator (Metal Gear Rising: Revengeance, Armored Core) and over 50 different animes series and films where mecha are featured
I'll be using Yanase's available designs, direct reference from my own copy of Xenoblade Chronicles X, and the wiki site for the game, as well as modelling videos and other appropriate resources to create my own Skell in 3D Model form.
MY LAST PROJECT
OPTIMUS PRIME RECREATION
This will be the second complex mecha I will have made, and with this Skell, I'm looking to improve upon my workflow from my previous project, a recreation of Optimus Prime, based on the Revenge of the Fallen Leader Class action figure -
This project made use of an on-hand reference and was modelled over a 28-week development cycle. It attempts to replicate the texture look of the toy, rather than a true-to-life robot. He also has a full transformation and was modelled with animation in mind.
To briefly con-crit myself, all of his detail has been replicated, even in lesser-seen areas, the topology is universally clean, and all of the pieces fit flush together with no clipping, even during the animation. However, from a texturing and baking standpoint, because the workflow relied entirely on floating/segmented geometry, and didn't employ the hard-surface philosophy of chamfered edges on its high-poly, this meant that the bakes were riddled with artefacts. And his dual energy swords didn't make it in.
I was also unable to set up a proper presentation reel for him. And because of the luxury of having an on-hand reference, I didn't have to run proportion checks, nor did I attempt to block him out beforehand as is the industry practice. Instead, I adopted a piece-by-piece approach which worked splendidly but can't be relied upon for all future projects, this one included.
With this cycle, I have 16 weeks to create the skell, as well as produce several pieces of weaponry for it. I'll need to get used to blocking out and proportion checking, as well as ensure the high poly meshes are modelled with baking down in mind, so chamfers and full geometry. This time, I want to capture a clean but still metal look with his texture, and I want to ensure a clean, errorless normal bake. The skells can also transform into vehicles, so I want to get that working too, and I want to present it within the Unreal Engine.
That's the goal. And as with most on here, if any of you are interested or have advice, feel free to share it.
Replies
BREAKDOWN
Humanoid Combat Walker, human-piloted. Movement includes walking, flying with aid of a module, and converting into an all-terrain vehicle for faster ground travel. The nature of the vehicle is often dependent on the armour build of the skell, some having treads, others having four wheels or two.
Operation of a skell is done from within a pod-like cockpit in the torso cavity. This forms the centre of the skell's body, from which the rig, vehicle components, armour and weapons get built around.
From the central cockpit, the skell is then built up in three stages -
Base Frame – The joints and skeletal pieces which dictate movement, as well as the housing for the pilot cockpit.
Vehicle Components and Flight Pack – Flight pack is universal, vehicle components vary per model
Armour – This plays into the overall character of the skell, as well as its functionality. The quantity and shape of armour denote each one as being either Light, Medium, or Heavy. The paintwork and light colours are cosmetic and can be customised.
Almost all conventional skells are built from the same frame, which is designed to emulate the articulation of a standard human skeleton. Some additional joints and components are added to enable the conversion to vehicle mode. The frame is otherwise deliberately generic to allow a wide variety of armour and vehicle customization.
The module for flight is at the back, mounted behind the shoulders, along with holsters for back weapons. It’s comprised of three visually apparent components – the wings, which sit folded behind and spread out when flight is engaged; a double set of thrusters, one primary and two secondaries, which get used for enhanced speed; and the twin (presumed) anti-gravity units grafted behind the exhausts, which generate the levitation. The light colour is cosmetic and can be altered.
Two different screenshots, taken from the game, of the formula skell fitted with different weaponry, and colour shaded in accordance with the above list.
All standard Skell models are fitted to be able to carry and wield as many as 10 different weapons, both of melee and ranged variety. This includes knives and swords, pile-bunkers, energy shields, rifles, missiles, cannons and several others.
Carrying of two on-hand weapons is mandatory. But the rest can be stripped down, and all weapons are interchangeable, allowing for full arsenal customization.
There is an assumed on-board targeting system too, and some form of camera setup to produce a virtual view of the outside world, similar to that of the display inside Iron Man's movie helmet. There is also a fuel tank of some description, which is fed into the weaponry and flight systems to power them.
All Skells can produce a restraining field around enemies past a certain side, which serves to bind the target and refuel the Skell. Where the effect is produced from, I'm still unsure.
BLOCK-OUT CASE STUDY - GUNDAM MECHA
Should hopefully be fairly short and sweet. It's divided into five sections, each one explaining a thought process to make the task easier -
Reference -
In the best-case scenario, and most available scenario, orthographic front, side, top, back images of the subject matter are best, as you can can get an accurate sense of measurement and relative proportion.
In this case, the schematic is providing this, along with the scale. I personally like having the front and back planes sitting in the centre.
Geometry -
The pieces themselves have been made in no particular order. I've tried to be minimalistic with the topology, and fair with the use of elements, but as can be seen with the calf and the helmet, I've done my best to create the silhouette with whole pieces. My rule of thumb is to keep separate any components which hinge or twist on the mecha itself.
Diagonals -
On the schematic, some of the portions, namely the legs, arms and exhausts on the backpack, are pictured with an angle to them. But modelling them whilst considering the angle is more trouble than it's worth, so what I did was perform all of the editing with the three portions at a hard vertical angle, using the side view of the mecha, which treated the limbs as if they were straight. Then when I wanted to test them against the body, I put them on a keyed animation which rotated them into their correct positions on the toggle of the keyframe slider.
Symmetry -
As the entire mecha is symmetrical, I've only modelled one side. If one half sits comfortably into the shapes on the picture, the other side will do the same.
Posing -
A parent and child link hierarchy gets used to test out the articulation after any existing links are broken off, the XForms are reset and collapsed, and the pivots are fitted according to hinges and sockets. I personally find the centre of cylindrical objects by insetting a central vertex into one of the circle faces, then snapping the pivot to that vertex. To centre it along the length, use a ring > connect to produce a central loop, and do the same vertex snap. Boxes are handled in a similar method.
Granted their's only half of him in these shots, but I like to think these prove the point on his articulation.
Proportion Checking -
With the reference material and knowledge of the skells in the game, the modelling of the Skell will be done in three stages -
This structure is in place so as to ensure the dimensions of each piece can be effectively informed (i.e. once the frame is built and proportionally sound, the armour can be modified around the size of the frame, and possibly vice versa)
The first step: the frame will be the most difficult to build, since all measurement will be largely approximate. There is no definite skell proportion schematic available online, like that of the gundam example, and whilst there is an available action figure of the Formula skell, with a 1/48 scale which I could potentially acquire for this piece, I've never tackled hard surface modelling without the luxury of an on-hand reference before, and I can't expect to always have one in future projects.
But I still want an idea of the units at play in order to feel confident. Which is why the first step of the blocking out was to establish a frame of reference, to inform the proportion.
Photo capture from Xenoblade Chronicles X, showing a skell in maintenance on a vertical stretcher. Most importantly, the legs are fully straight and vertically aligned.
Forewarning, this approach is quite rudimentary. It's the man vs. machine comparison, that is to say, using units of 'man' to gauge the skell height, and as modelling experience has taught me, once one dimension is sussed, the others soon follow. The skells in the game have an at-ease/ready-to-roll standing pose when they're being operated or are dropped to one knee when stationary, which isn't helpful for measuring true leg height; the splay from the legs makes height measurement inaccurate. However, there is is one skell which is undergoing maintenance in the game, which has straight legs.
Photo capture of the player character standing in front of the skell in maintenance, who at head height is roughly as tall as the top of the skell's shin. This has been used to roughly sketch out the proportion of the rest of the leg in the diagram on the right.
With the character put next to the skell - I'm assuming my character's standing height to be grown man-size (1.8m) - he comes up to about the shin. Rounding the number up to 2m it reaches the lip of the calf armour. Stacking him up, we get a measurement of about 4 1/2 metres total from foot sole to ball and socket joint at the top of the leg.
Using this measurement of height, and a rough unit of 1 Head width = 20cm, with which the snaps have been set to, the blocking out started.
Photographs from a paint over of the Formula skell action figure by Zankuro on Hobby Forever. These shots give a good look at the underlying frame, including the joints and connections.
Someone by the username of Zankuro has an entry on a french website called Hobby Forever, showing his paintover of the skell toy. The photos include the skell stripped of armour, and the leg portion isolated and flat.
Left: biped rig in 3DS Max vs. one of the refernece images for the leg, as well as the core located on the chest of the skell alongside. Right: Cylinder meshes placed over the hinges on the leg, blocking out pivot points.
This leg piece has been used as a starting point. The reference has been sized in relation to the 3DS Max, biped rig, which has a height 1.8m. Cylinders to block out the pivot positions of the leg came next. This leg has five components - the thigh and the calf, the ball of the ball-and-socket joint at the top, and a pair of hinges behind the knee which dislocate the calf and switch backwards for vehicle mode.
The core of the skell was also modelled early on, as seen on the left, estimated to be about 1/2 metre in diameter.
Left: Leg ensemble, showing topology considerations. Center: Partial render of the leg portions, with chamfered edges and turbosmooth applied. Right: Both legs, with feet, compared against the rig.
I was hard not to model the high detail, but the resultant piece is still something of a hybrid: the appropriate sizing and silhouette but topologised with a high polygon version in mind, and the edge flow gives away, plus there are inset details on some of the pieces, but only the mid-forms and nothing minute. Put next to the biped, it reaches the upper part of the shin.
Left: The upper portion of the skell, and on one of the shoulders, the player character with his head down, showing the size difference. Right: a unit segmentation in iterations of human head width (20 cm approx.) of the skell from shoulder to shoulder. Total width of approximately 2.6m
It turns out that the skell also appears to be fairly conformant to 20cm units, as a grid study of the shoulders and backpack shows that a good few of the pieces align to the spaces. From shoulder to shoulder it's about 2.6m, with the helmeted head being a metre wide, and the hinges of the backpack coming to 2.2m wide. It's harder to gauge the other dimensions since the whole upper portion slants downward with the pod in the centre.
Scene shots of the backpack block-out ensemble, coupled with a very approximate size for the internal pod, head, and shoulders
The flight module portion of the backpack isn't standard, nor is it a permanent fixture, and indeed the skell on the stretcher lacks them, instead of having cables feeding into the backpack. I've used the shapes, coupled with the core piece to start mapping in the centre of the frame and the head.
From left to right: Photo capture of the arm of a parked skell in the game, bent backwards at the elbow for vehicle mode, and the character sitting beneath for scale. Side diagram of the arm, straightened, along with a piece of armour from the wrist, measuring roughly 5m in length. Block-out of the arm components, from shoulder to hand, in 3DS Max.
I've used the same measuring system for the arm with the help of another skell, parked in vehicle mode, where the arm was low enough to compare. The arm has 5 hinges: three at the elbow, two at the wrist and three on the upper arm for its full range of articulation between modes.
Isometric, side, and front screenshots of the early assembly, unposed, with the biped beneath as comparison.
And these are the assembled components, roughly fitted together. Granted some pieces are missing, but the key features are in place, and the rest can be built around them. An update on the block-out will likely be on the next post, very likely with the remaining pieces in place, as armour and colour samples will come next.
Armour
The armour of a skell, contrary to most mecha of similar proportion, has very clear segmentation. Since skells are designed to be customisable and versatile, a sparser and more easily removable armour set is used. Rather than full-body covering, the armour is plated and placed only over key areas, such as the limbs, and doesn't obstruct joints. All skells have about 20 uniquely shaped pieces of plating used for their armour, and its through the shape and bulk of these pieces that the nature of the skell's character and capacity as a combat mecha are shown.
Takayuki Yanase's skell concepts, arranged and categories by their weight classes - Light, Medium, and Heavy
As skells get heavier in make, their armour aesthetic changes, in terms large forms, thickness, and shape. The heavier builds also take advantage of the innate bulk of their vehicle components to gain even more volume to their frames.
From the above concepts, two of the skells have been shortlisted - The Light Class Formula Skell, which is the poster-boy skell for the game and has a motorbike vehicle form, vs. the bulkier Medium Class Inferno skell, which has a chunky armour build without obstructing the underlying frame as much as the heavier builds do, and has an armoured truck vehicle form. These two are interesting because in several places there have near-identical armour pieces, namely on the feet, arms, and chest. However, they do have greatly differing armour elsewhere. The formula has sloping, streamlined pieces, and the Inferno has wide, cubic and hexagonal plating, not including the vehicle components.
My own drawings of Left: the wheel holsters for the Inferno Skell, with diameter measurements on the wheels to give scale. Right: Drawings of the side and back of the skell flight module.
For the vehicle components, and the flight module, being part of the transformation meant greater attention being necessary to proportions. Some further sketching was also done, to establish their shapes and size. These pieces also have armour plating, some of it universal, like the 'aerodynamic' portions on the sides of the flight module, but others specific, such as the wheel housings on the Inferno. Indeed the Formula and the Inferno utilise different vehicle forms, which necessitates different parts for the back and legs.
Despite that, these two have the most similarities between any two given skells from the concepts above, so they'll be the test cases for blocking out.
The pieces started as colour coded planes, roughly in a similar manner to the diagram of the armour breakdown. Due to how thin the pieces are, volume wasn't too necessary, to begin with. What was necessary was creating instances of each piece, as shown. Placement of the planes on the armour, especially when posed at angles, makes editing awkward, plus, constantly having to refit them, or they remove them to unwrap and bake their detail in the future, would lose a lot of time.
An ensemble of the Inferno armour pieces kept uniform for ease of editing. Editing them will cause the same changes to be made to their equivalents on the skell.
Giving them depth came afterwards. Their placement and size were determined by references, the game skells, and some trial and error. Un-transformed instances were produced with each one, which will be the versions which get unwrapped. As with the frame, the pieces are topology-aware, so that when the time comes to produce high detail, there are no smoothing errors.
Left: Render taken in 3DS Max of the Formula Block out, with the figure beneath to show scale, the armour pieces to the left and the formula reference behind. Right: Screenshot from 3DS max of the Inferno Block-out, with edges showing to demonstrate the topology with a chamfer and turbosmooth modifier duo applied.
With the pieces placed, this is the look. Once again, the block-outs have only been modelled on one side, but have been temporarily mirrored to demonstrate the look of the skells with their armour. The widened stance in these images is a result of the underlying frame being keyed up to enter a natural stance, and the armour pieces linked to them. There were two block-outs made, one of each of them, and working appropriately for the carry-on to high detail.
Custom colour scheme concepts for the Formula skell, inspired by the natural colours present in Xenoblade X's predominant five regions.
Paint and colours have also been considered for each of them. As mentioned in an earlier entry, all skell armour sets can have four colours incorporated, plus one for their lights and visors. Using the concepts to identify where these colours would be placed, five unique palettes have been created, one for each of the five biomes within Xenoblade Chronicles X's open-world - Primordia, Noctilum, Oblivia, Sylvalum, & Cauldros. The colours take from the flora and visual luminescence of the regions.
Custom colour scheme concepts for the Inferno skell, inspired by the natural colours present in Xenoblade X's predominant five regions.
This has been done for both skells. In-game, the variation of each model do switch up the placement of the colours as well, but as a guide, these are appropriate. And have been a help in deciding which model will be carried forward.
Pose
Screenshots from 3DS Max, showing the progress on the skell, its unposed state for editing, and how its hierarchy for posing has been set up.
In its editable state, the skell's components are straightened to conform to the 3DS Max axis. However, this isn't an accurate idea of how an in-game skell will appear, so, the parts have been linked together using simple parent and child hierarchy, with their respective pivots in place for articulation. Then, on the animation slider, there are key frames in place, for testing three stationary poses which skells adopt in-game -
Free-Standing
A Photo, taken from the game of three idle skells: Inferno, Lailah and Formula, out in the field.
The classic pose of a skell is its free-standing form, looking ready for combat, stance wide, arms and legs a little bent, armoured and ready. There is some small difference between the weight classes, as the lighter ones, with their relatively small frames, put one foot slightly forward, and have a narrower stance. Contrastingly, the Inferno needs a wide stance to allow for the girth of the wheel housing on the thighs and has its legs more bent to accommodate the weight on the back.
Left: An inferno skell, colour-dissected into key areas of interest for the pose. Right: side and front profiles of the skell model, posed to replicate the shown stance
Overall, this recreation is suitably accurate, but the shoulders need to be further back, as they can be seen at angles in the picture. And the fingers haven't yet been posed. It's also tricky to gauge the angle of the central line running up the pod, as the pod isn't vertical inside the frame, and the central components are modelled directly on top. But this angle seems close.
Kneeling
A photo, taken from the game of three skells in standby mode: Inferno, Verus and Formula, out in the field.
When the skell is in the field, but the pilot has to eject while the skell is standing up, the skell drops to one knee, and enters standby. In order to release the cockpit, it's chest armour lifts and the housing around the pod loosens to allow it to slide out. Two hatches then open and the pilot can eject safely.
Left: An unpiloted inferno skell, colour-dissected into key areas of interest for the pose. Right: side and front profiles of the skell model posed to replicate the shown stance
In practice, this looks a lot like an empty proposal -
All skells drop their right knee for this pose. As for the recreation, this one is a little rougher, as the model had just had its pod and housing properly formed from a very vague block-out. As such, the shoulder are still tense, and the legs are in line, wherein the picture they are a little spread.
Vehicle
Left: A photo, taken from the game of three skells in vehicle mode: Verus, Formula and Inferno, out in the field. Right: An inferno skell in vehicle mode, colour-dissected into key areas of interest for the pose.
Third and final, the vehicle mode. In this mode, the skell's centre of gravity lowers to the floor, it's frame levels out into a horizontal form, and its limbs are tucked away to give way to the wheel components. Transformation varies from model to model, but the Inferno skell is modelled after an armoured truck, with a pair of wheels in a pack behind its hips, and the front wheels resting in front of the legs, giving the impression of massive thighs.
Breaking it down -
Side and front profiles of the skell model posed to replicate the vehicle mode
For a general critique, the chassis needs to be lower, the pod needs a flatter angle, and maybe some of the back components need to be reconsidered to avoid clipping, but otherwise, it's a close one. This one was the hardest and required the most tweaks, and still is being tweaked as the block-out is refined in the high-poly.
From top-left to bottom-right: base editable pose, free-standing pose, standby pose, and vehicle mode
Here they are together in perspective. The free-standing pose will be the priority, followed by vehicle, and then the standby pose. Hopefully, all three of them can be incorporated, and maybe animated between. But that's more of a hopeWeaponry
Scans from the artbook - Xenoblade X: The Secret File: Art of Mira, showcasing a variety of concept art for the skell weaponry featured in Xenoblade Chronicles X
Weaponry in Xenoblade comes in two varieties, weapons to be used in melee situations, such as blades, tomahawks, javelins etc., and firearms to be used in ranged combat, commonly grouped into rifles or missile launchers
The scope (in design terms) of what weapon options are available is very variable. On the simplest end are handheld grenades and flash pods for offhand weaponry, and at the far extreme is heavy-duty superweapons which can occupy the entirety of the available space on the back and shoulders of the skell.
Aesthetic is also due for consideration. The weapons in-game come from a couple of different manufacturers, each of which has a recognisable aesthetic in its weapon lines. Due to there being alien resources and themes of greatly advanced technology and science-fictional breakthroughs, they tend to shift away from the design of earth weapons and venture into the more creative side.
Weapons from other manufacturers also exist but aren't as easy to come by.
Left: Render of an Inferno skell, wielding the B-Gatling shoulder weapon. Right: Concept art for the B-Gatling schematic, highlighting details and functionality, taken from the artbook - Xenoblade X: The Secret File: Art of Mira
Some skells have weapons which are associated with them or are tailored to their combat abilities, such as the melee-oriented Verus skell and it's accompanying G-Buster shoulder weapon which delivers a powerful blow, as well as causing a Stagger. The Mastema meanwhile has a M-Sniper, to complement its ranged attacking ability. The Inferno has the B-Gatling 5-Barreled Rifle, which may be made later to accompany the model.
Top-left: A toy equivalent of a sword Skell weapon. Top-right: One of my own drawings of the sword, replicated from the in-game model. Bottom Left: Concept art of the G-Buster schematic, taken from the artbook - Xenoblade X: The Secret File: Art of Mira, highlighting details and functionality. Bottom centre: One of my own drawings of the G-Buster, replicated from the in-game model. Bottom Right: A toy equivalent of a Skell beam shield.
Three weapons have been picked out -
Sword - An on-hand melee weapon made by Sakuraba, with a folding blade. Its design is reminiscent of tactical knives used in the military.
Gravity Buster or G-Buster - The weapon commonly wielded by the Verus Skell, also developed by Sakuraba. This giant tomahawk is longer than the skell is tall, and certain iterations see it transform into a flail. The magenta interior registers in the game as a glowing strip of horizontal light which travels from hilt to tip. An effect which is hopefully going to be replicated
Beam Shield - A piece of support equipment made by Sakuraba. This guard sits on the forearm and can be used to generate barriers to elements. The appeal of this alongside the other two are the cylinders, which will mean different topological considerations.
Twin screen captures of the process of modelling the Sword and G-Buster weapons, showing their topology and lit appearance in 3DS Max
The high detail meshes were made with the help of flat diagrams, traced directly from their proportions in the game. Using these, the details were mapped out with planes, then extruded and bevelled, and finally partially retopped to facilitate a chamfer and turbosmooth modifier combination. The sword is two pieces, the pivot on the tip portion placed to enable the blade to switch. The G_Buster is an arrangement of segmented elements where there is metal, with an underlying mesh beneath it to be the area for the emissive light. Symmetry was also made use of, but some of the detail has deliberately been left out, to be applied in the texturing stages using greebles.
These two pieces were sped through development for the sake of having testing models for the academic research. The beam shield is still in development, which is why it isn't shown here.
Twin screen captures showing the low-polygon versions of the models, against their high-detail equivalents, along with their unwraps.
The optimisation was straightforward. With a good amount of the detail being spread over a relatively large flat space, a great deal could be baked down.
Both unwraps are arranged to have no overlay, instead of imitating some form of symmetry in their arrangement. For example, the two sides of the sword mirror each other, as do their neighbouring pieces. The islands are arranged and packed as intuitively as possible on the sword. Meanwhile, on the G-Buster, the two main planes of the sword are peeled to shape, arranged vertically and aligned with each other horizontally, and fit as big as possible. The slightly inefficient placement of the side faces is done with purpose too, they correspond vertically to their counterpart edges on the buster. All of this is to make it possible for a panner node to be set up in Unreal engine to cause the emissive light to travel down the face of the weapon.
Normal, Height and Ambient Occlusion test bakes for the Sword and G-Buster, produced in XNormal.
Lastly, before moving the models over to Substance Painter, these maps were baked out in XNormal to check everything was in order for both of them, and the overwhelming majority of the normal data appears to be translated properly. These won't be used for later stages, apart from the G-Buster normal map to create a mask for its Emissive texture.