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Skirmisher (Sentry Gun)

This is the SFM version for the Skirmisher (Sentry Gun).


It's a long-range sentry gun that fires high velocity explosive rounds.


This item was originally planned back in 2015, but I shelved it because I did not feel confident in the design(and my skills). I decided to revisit it and finish it off now.

The Skirmisher was designed around the weaknesses of the Stock Sentry Gun. Instead of snappy targeting and high sustained damage, the Skirmisher was intended to be slower, higher burst damage, and longer range.


Skip to the Notes section if you don't want to read the background behind this item.


This was, perhaps, the most ambitious item I've ever created for TF2. I knew I would be biting off a lot when I began work on it, I just didn't know exactly how complicated the Sentry Gun was.

The original design was to make some kind of cannon, but at the outset I was unsure exactly how it was going to look. I chewed through many designs trying to find something that meshed well when paired against the Stock level 1. Eventually, I realized that the Sentry Gun is really its own class, and therefore decided to draw inspiration more from the developer commentaries and insights when considering the design.

What often gets lost in translation when making TF2 items is the attention to palette and silhouette. The weapon in question needs to match a certain profile to be distinguishable on the battlefield. It needs to conform to the muscle memory built up by players from over a decade of play. You can't just go crazy here.

When designing the Skirmisher, I wanted something that evoked the feeling of a Sentry Gun while also being wholly unique in its own right. It needed to match the shape of the Sentry Gun at each stage, but also stand out and be identifiable in the heat of battle.

After I made these considerations, and started infusing the Stock Sentry Gun into the design, the work on the gun became much easier. Where it was once confusing and difficult, it became almost effortless. Everything just started fitting together. I was not designing the Skirmisher, it was telling me how it was supposed to be designed. It wanted me to finish it.


Another interesting road bump was the texture work. It's not enough to have a good texture, you actually need three textures that fit together seamlessly. This is primarily due to the fact the sentry needs to transform between stages. Once the level 1 texture was done, I had to painstakingly carry that texture over to the level 2, and then texture the level 2 so that it lined up with the seams on the level 1. The same thing happened for level 3, only now it had to be in line with both level 1 and 2. Again, a bit headache inducing the manage, but ultimately it came together quite nicely.


For animations, I had to make several passes to find the right technique. The main issue was getting the legs to stay firmly planted on the ground during the build and upgrade animations. I ended up building a rig solely made up of IK targets and constraints, and letting Blender do most of the heavy lifting in terms of animating all the complicated motions. Once I had the rig situated, the rest of the animation work became fairly straightforward.

Animations had to be baked from the IK rig onto the heavy rig, and then rebaked again onto the gameplay rig. It's tedious to do, but the effect is very striking. The animations look nice, are smooth, and feel professional. I find myself pulling them up from time to time just to watch the transformations again.


The blueprint was an interesting challenge, as there was a lot going on between the blueprint paper and the line model. I had to load up the level 1 sentry, and then trace it with geometry to get the basic frame of the line model. Then I had to create a texture map and then remap the line model as a texture mesh, placing circles and shapes over the original geometry.

The blueprint paper itself had to be made from scratch, and is actually a composite of several textures and even meshes all being pressed into the paper. I had to use things like Blender's FreeStyle system and various fonts to emulate the similar industrial quality of the original Sentry Gun's blueprint. I ended up looking a lot of reference material for insights in to how blueprints in the real world are normally formatted. The paper contains a few little easter eggs, though I don't know if they are legible at this texture quality.


Finally, the toolbox was something left over from when the Skirmisher was part of a set. Originally I had planned to make a set of buildings, all sharing the same toolbox. The original toolbox design was something of a large plastic design with several locking mechanisms. I deemed this too modern, and ended up using old school toolboxes from the 1940-50s for inspiration. The cantilever design seemed interesting and simple, so ultimately it was the style that stuck.


Why the wall of text? Partly because it was a fascinating journey for me, and also that others who decide to embark on the sentry gun journey might glean some useful tips from my experience.

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-The rig is entirely custom, meaning it won't snap neatly to the Stock Sentry Gun.

-At each stage of the upgrade process, the sentry gun is supposed to gain longer range. This is reflected by the change in the laser point between the stages. At level 3, the laser sight and camera become a full radar dish, which extends from the top of the sentry. It is modeled after the wrangler's similar radar dish design, primarily to imply that this extension is not a weapon.

-In TF2, the sentry gun is swapped to a "_heavy" model when performing the initial build and upgrade animations. This is mainly to allow for a complicated build animation. This gets swapped to a much more stream-lined base model with significantly less bones for gameplay purposes. As such, the sentry gun contains 6 different models, for each stage of the upgrade process. The order is as follows:

lvl1_heavy(build) -> lvl1 -> lvl2_heavy(upgrade) -> lvl2 -> lvl3_heavy(upgrade) -> lvl3.

-Due to the way the level 1 was rigged to accommodate the build animation, the support arm underneath is not linked up with the swivel bone that rotates the main platform. If you decide to rotate the sentry gun using the "swivel" bone, remember to also rotate the "support_base" bone to correct the arm. You can also use the "layer yaw" sequence to rotate the sentry gun.

-For pitching the sentry gun up and down, use the "layer pitch" sequence.

-Level 2 and 3 contain firing animations that cycle the shells in the back to simulate a reload. These do not sync at the end of the animation in SFM for some reason, causing a notable jutter on the last frame. I do not have a solution to this. It appears to be a side effect of porting from TF2 to SFM.


Includes:
weapons\c_models\c_cant_toolbox\c_cant_toolbox.mdl
weapons\c_models\c_cant_toolbox\prp_cant_toolbox.mdl
buildables\bui_cannon_turret_lvl1\bui_cannon_turret_blueprint.mdl
buildables\bui_cannon_turret_lvl1\bui_cannon_turret_lvl1.mdl
buildables\bui_cannon_turret_lvl1\bui_cannon_turret_lvl1_heavy.mdl
buildables\bui_cannon_turret_lvl2\bui_cannon_turret_lvl2.mdl
buildables\bui_cannon_turret_lvl2\bui_cannon_turret_lvl2_heavy.mdl
buildables\bui_cannon_turret_lvl2\prp_cannon_turret_ammo_belt.mdl
buildables\bui_cannon_turret_lvl2\prp_cannon_turret_shell.mdl
buildables\bui_cannon_turret_lvl3\bui_cannon_turret_lvl3.mdl
buildables\bui_cannon_turret_lvl3\bui_cannon_turret_lvl3_heavy.mdl

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