Alex Vlachos

I joined Meta's AR/VR team yesterday. Can’t wait to get my hands on some new prototypes! Super excited about our product roadmap!

Valve artist @rich_lord gave a great talk at SIGGRAPH HIVE 2023 that every rendering dev should watch. Tons of inspirational moments for shader development. The fractal sequence starting 29 minutes in is impressive. youtu.be/R-S9d-qFRHM?si…

@swainrob No license. Zero patents. Originally written by Iestyn Bleasdale-Shepherd for Portal 2 with some minor tweaks for VR (original code was aimed at dithering Xbox 360). We shared it with the industry as part of our VR brain dump in 2015 at GDC. Free to use any way you want.

.@AlexVlachos what is the license of the dithering code in your 2015 GDC talk? Slide 49: media.steampowered.com/apps/valve/201…

@thatJaneNg @Invertednormals @plumplumcurse @ErikRobson The advice I always give family and friends is to start with @JLCollinsNH book, "The Simple Path to Wealth". The first step is to watch this video: youtu.be/T71ibcZAX3I

@EricWescott1 Only one frame needs to be critical to drop 2 levels. Max is used to decide to drop 2 levels when we're extrapolating frames, but we only extrapolate when a frame is above the extrapolation threshold. But you'll need someone at Valve to verify.

@AlexVlachos I saw your GDC talk on adaptive quality and why you use linear extrapolation. I wasn't sure on how exactly a parameter (0-1 real #) would be factor to that calculation. As far as critical vs max you think they ended up being having the same behavior of just -2 quality levels?

@AlexVlachos Any chance you could shed some light on what exactly these dynamic resolution parameters for HLA do outlined in this Reddit post reddit.com/r/OculusQuest/… Specifically: vr_fidelity_threshold_frame_percent_critical vr_fidelity_threshold_frame_percent_extrapolation

@EricWescott1 Not sure if that's helpful. I wrote that code over 5 years ago. Remembering the details is difficult at this point, especially because I can't just look at the code.

@EricWescott1 Extrapolation is about guessing what the cost of the next frame will be. I used linear extrapolation to guess at the next frame's cost to preemptively drop one quality level when the extrapolated estimate exceeded that limit. Again, assuming I'm remembering correctly.

This is a quarantine gift from the gods! Can’t wait to make my way through all of the developer commentary in Half-Life: Alyx! Jason hired me at ATI 22 years ago and then recruited me to Valve 8 years later. Technical writing is his superpower. This is going to be amazing.

A new software update will increase the visual fidelity on the Reverb G2 and other WMR headsets, by improving corrections made for chromatic aberration and more. uploadvr.com/reverb-g2-visu…

Here is a short write-up of some visual quality improvements I’ve been working on the last few months at Microsoft for the HP Reverb G2

My career started in 1997. I remember when we started putting heat sinks on GPUs before anyone called them GPUs. And let’s not forget about the QA guy who ran out of thermal paste and used a half-chewed Tootsie Roll instead. Spoiler alert: it didn’t work. Good times at ATI!

@mcnabbd @_AlecJacobson Yes. The Animusic demo. About 18 years ago. It was a combination of statically carved shadows and dynamic stencil shadow volumes. I described the carved shadows in this talk at around slide 22: alex.vlachos.com/graphics/Vlach…

@_AlecJacobson @AlexVlachos am I remembering correctly?

Sure you can compute shadows in screen space or using ray tracing, but why not do it the hard way? Extrude all of the silhouette and contour edges into a shadow volume triangle mesh, mesh Boolean that against the original mesh, and finally shadow triangles via winding number.

@akipman Week one of many!

welcome to the team. very excited to collaborate with you on this journey [)-)

Very excited to share that I joined Microsoft today as a Partner Architect in Mixed Reality (HoloLens, VR, etc.)! Been looking forward to this for a while! More details later.

After seeing Animusic's Pipe Dream at @siggraph 2001, they offered my team at ATI all their art assets to build a real-time demo that we shipped one year later for Radeon 9700. Now I learn this! @Intel built a fully functional robotic replica! Amazing! youtube.com/watch?v=JLdB0W…

@CMDannCA My other test scene was high res versions of left 4 dead zombies in their idle animation loops. I had about 10 characters in a circle with the player in the middle in a small room with no doors or windows. Some coworkers were not pleased.

@AlexVlachos I would have rendered a bunch of these guys. They used to scare me when I was younger haha.

Half-Life VR, fun fact. I was the first person to import and render a Half-Life 2 model in VR. It was Alyx’s giant robot dog in his idle animation. April 2014. I fell asleep that day with my HMD on. Woke up to a giant robot dog aggressively staring at me. Nearly crapped my pants!

@MattFiler @matttwood My kids were very young and still not sleeping through the night. I was sleep deprived and mildly hallucinating most of the time. Involuntary naps at my desk was the norm for a while.

@AlexVlachos @matttwood The prototype HMD looks like it weighed a ton, exactly how tired were you?!

@gabsfrmarqs @ValveNewsNetwor This was early VR development that led to Aperture Robot Repair and The Lab.

@matttwood Yes I did. And it was only a few weeks after having an HMD at my desk. VR was still a very new concept. Waking up to that was frighteningly realistic at that point in time.

@AlexVlachos You fell asleep with your hmd on.