Interview With the Engineering Team

September 7th, 2023

Ever wonder what goes into the creation of a project like the Build Calculator? We sat down with Sam Cohn, one of the founding Engineers, and asked him a few questions regarding just that. Let’s take a look at what goes into the making of this amazing tool.

What brought you and your brother to this project?

Being close friends with another member of the Diablo Builds team who saw an opportunity. Sam and his brother Josh would often play Path of Exile with him. After finding Path of Building, he realized that he wouldn’t be able to play the way he wanted to without this tool. So he pitched the idea to Josh and Sam to create a similar tool for Diablo 4 sometime in February 2023.

How long have you guys been working on the calculator? Has it become kind of a passion project for you and your brother and anyone else involved?

After a couple months of planning, the project started in April the same year. It quickly became a passion project for the three of them while they started laying the groundwork. Significant amounts of time were put into making a useful tool that fits their vision. Even without being able to play the game as much as they would like they have still dove deep into it to provide as much accuracy as they can.

What made you decide to do this project for D4 specifically versus other ARPGs?

With an extensive background playing Blizzard games and the intersection of the ARPG genre from their time playing Path of Exile and using the Path of Builds tool, it all made sense. Along with the guaranteed content that Blizzard would put out for potentially years to come, the timing couldn’t be better.

What kind of gaming experience have you had in the past and has it changed since you’ve been on this project?

Sam was heavily into World of Warcraft and Josh was more interested in ARPGs like Path of Exile. However, given that they have full time jobs as well as putting significant amounts of effort creating the Diablo Builds Calculator, they haven’t had much time to game since everything got started.

What was the learning curve like for creating the calculations for a game you have never played yet? Was the general ARPG knowledge you already had integral for this process?

Having a formula or understanding them is invaluable to it but is just a starting point. That is a small portion but still important. Modifiers were a different story. Coming up with a model for that was much more difficult. It took a long time to figure out. They had to go through multiple iterations until they had a system they were happy with.

How many people are on the Engineering team and how much time do you generally put into making and updating the calculator each week?

There have been a few different people that have worked on the UI side of things with varying time spent working on the project. Sam and Josh have been the two working on the math of the calculator both of which put about 30 to 40 hours a week into this project while also working a full time job.

Do you have different groups of people taking care of individual sections of the calculator or does everyone just work on everything at the same time? ie. Character tab, Paragon, Skills etc.

The Engineering team is divided up with Josh and Sam handling the background math while the others work on some of the more specific things like the paragon board, which has turned into its own type of monster. Josh focuses more on the data and Sam is more design oriented with the calculator. Though they have some parts delegated, they also have people to help where they are needed.

What does not having access to the API do in terms of how you are able to update with new items released? (Unique items, new aspects, seasonal changes)

With no access to the Application Programming Interface (API) of the game, they are forced to work manually when compiling some of the data needed. Most of the new content will be teased allowing you to see what items and new changes will be coming, allowing them to build a basic “scaffolding” for the calculator to work with. Ideally they have basic information on how it works and how it is expected to behave then once the season starts, they go in to test the interactions the new content has with various things. Finding the uptime on buffs and abilities is important in this step.

Could you share some details with us about the experimental tests used to make the calculator more accurate? ie. Armor.

There are two ways of getting data from the game. 1.) Changing things up and seeing how tooltips change. 2.) Changing things up and seeing how much damage you actually deal or damage dealt to you depending on what you are testing. A lot of data comes from the community and has been very helpful, however, it has to be confirmed beforehand to make sure no confusion that may have happened in the community makes its way into the calculations. They also had an interesting time finding that abilities have a tenth of a second frame speed. This was important with some of the damage calculations. They did this by taking video capture of gameplay and looking at the frame data from there.

How frequently do you guys push updates out for the calendar?

Currently there are constant updates as it’s still technically under development. Once the Build Calculator is fully developed the team will be aligning their updates with Blizzard’s updates. Patches from Blizzard will mean information changes to items or game mechanics and that will have to be adjusted in the Build Calculator.

These were a few questions we thought might be interesting to hear about from one of the devs. Thanks to Sam for taking the time to answer these questions for us we now have a bit more understanding of what goes into making the Build Calculator as well as how this project came into being.