{"id":3000,"date":"2020-05-26T12:00:51","date_gmt":"2020-05-26T19:00:51","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/directx\/?p=3000"},"modified":"2020-10-23T15:58:56","modified_gmt":"2020-10-23T22:58:56","slug":"gears-tactics-vrs","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/directx\/gears-tactics-vrs\/","title":{"rendered":"Iterating on Variable Rate Shading in Gears Tactics"},"content":{"rendered":"

Gears Tactics <\/em>is the very first game to ship with support for DirectX 12 Variable Rate Shading<\/a><\/u> (VRS), one of the major features in DirectX 12 Ultimate<\/a><\/u>.<\/p>\n

VRS let Gears Tactics<\/em> achieve large performance gains \u2013 up to 18.9% (!) \u2013 on a wide range of hardware with a minimal impact on visual quality. Check out this guest post where Jacob Nelson and Cam McRae share implementation details, performance data and future ways to expand VRS.<\/p>\n

Iterating on Variable Rate Shading in Gears Tactics<\/span>\n<\/strong><\/p>\n

Jacob Nelson, Programmer at Disbelief<\/em><\/p>\n

Cam McRae, Technical Director at The Coalition<\/em><\/p>\n

Gears Tactics<\/em> is a fast-paced, turn-based strategy game set in the universe of one of gaming\u2019s most-acclaimed franchises\u2013 Gears of War.<\/p>\n

<\/p>\n

One of The Coalition\u2019s primary goals on Gears Tactics<\/em> was to reach a wider audience on PC by reducing the hardware barrier to entry. This led us to look for new solutions to improve performance that didn\u2019t entirely involve sacrificing visual quality. We landed on Variable Rate Shading (VRS), which gave a generous performance boost with minimal quality loss. In this article we\u2019ll detail our process of iterating on VRS to achieve a good balance of quality vs. performance.<\/p>\n

Availability of VRS is based on hardware. To support our goal of reducing the hardware barrier to entry, we wanted to include the broadest range of hardware in our VRS implementation. For this reason, our implementation is exclusively Tier 1, which lets us set a shading rate per draw. For more background on VRS, refer to this blog post<\/a>.<\/p>\n

Because our usage of VRS did not extend past tier 1 we needed to determine which rendering passes (Gears Tactics<\/em> uses Unreal Engine 4) could support VRS, as well create new ways to determine when to reduce the shading rate. We found we could benefit from VRS throughout the renderer, including some full screen draws.<\/p>\n

Evaluating the Rendering Pipeline<\/strong><\/p>\n

In our initial investigation, the base pass and translucency stood out as large potential for gains compared to most other passes. We enabled VRS for all draw calls in the base pass and the translucency pass and immediately noticed the artifacts were too severe in the translucency pass.<\/p>\n

We determined our next step would need to be evaluating which passes had the most promise for gains from VRS and then testing multiple shading rates on those passes and excluding any that had artifacts. Passes that relied on accurate pixel information were one cause of these artifacts.<\/p>\n

To figure out which had the most promise, we enabled VRS on all passes and then narrowed down in PIX the areas that showed a benefit. These areas were:<\/p>\n