Conversion Intro was the last map in Portal 2 to take 10 portals or more to complete. Now, every map in both single-player and cooperative campaigns has a least portals record that can be represented in one digit.

This route is a result of a seamshot research leaded by me and mlugg for the past week. We've discovered how they work and what's required for them to exist, which improved the methodology of looking for them, which ultimately allowed us to find a seamshot in Conversion Intro that makes this route possible.

In short, non-axis-aligned brushes (level geometry) have a faulty ray collision detection. It uses a small distance (0.03125 units to be exact) to virtually shift every plane of the brush away from it, creating an illusion of it being slightly larger. However, because of the incorrect math in the collision code, planes facing the same way to the ray are shifted into the brush instead of away from it. This means that if you shoot very closely to the edge/wall of the non-axis-aligned brush, a virtual "opening" is created as long as you're not facing the wall which creates this opening. This allows us to literally shoot through corners and walls if conditions are right.
There are some technical difficulties to it, which I don't want to explain here. If you want to learn more about seamshots, read this article: [ Ссылка ] (WIP)

With advanced knowledge of seamshots, I was able to locate a shootable seam between a wall and a frame of the elevator shaft window that leads to the portalable wall on the other side. After that, it didn't take long to find a route that would save some portals.

I started the same way as in the old route: navigate through beginning, get to the office area, ride the elevator to the conversion gel test. Now, I need to get outside of the middle area, because you cannot shoot the portalable surface through the seamshot neither from there or from catwalks. I used two portals for this, placing one in a way that would allow me to perform gel stucklaunch, but more on that later.

Next, I aligned myself for the seamshot. Here are some tips for it in case someone wants to attempt this:
- Your Y position should be in a range between -191.96975 and -192.0, preferably as close to the first value as possible. X position isn't as precise, just stand in the spot I do in a video and you should be fine.
- Your pitch angle (first value in cl_showpos/sar_hud_angles) should be close to -50. Not very precise, but try to not deviate more than half of degree.
- Your yaw angle (second value in cl_showpos/sar_hud_angles) should be VERY close to 0, and has to be negative. The precision required for this value goes as high as 5 decimal places.

Once I hit the seamshot (the giant metal sphere is not solid btw, the only solid thing I'm shooting through is just the seamshot spot on a window frame), I go back to the floor portal, pass through it to get into the shaft, and prepare the floor portal in it for gel stucklaunch.
This is a funny glitch that had no application in a single-player campaign until now. Basically, if you stand on a floor portal, gel particles going into it can occasionally get stuck on you. This, for whatever reason, allows them to gain vertical speed, which then you can release by walking or jumping away from the particle. Thanks to it, we can launch conversion gel particles close to the exit and place our last portal over there to finish the level.

I'm very happy that our seamshot research paid off and brought not only a 2 portals save, bringing total number of portals needed for Inbounds NoSLA run down to 71 (for Inbounds SLA that would be 64), but also a very nice TAS route, which brought Conversion Intro TAS time below the 30 seconds barrier (!). Honestly, this map has been ruined in quite positive way!

Now that we know precisely how seamshots work, more wild routes involving shooting through walls and corners have a chance to appear in the future, so stay tuned.

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