Portal: Prelude RTX: Nvidia’s Impressive Showcase of RTX Remix Technology and RTX IO
Portal: Prelude RTX is a remarkable demonstration of Nvidia’s RTX Remix technology, which elevates the once Source mod for Portal with stunning visual features and technology comparable to high-end AAA releases. It is truly a spectacular experience, and we can hope to see more path-traced remasters in the future as the RTX Remix modding tools near release.
What sets Prelude apart, however, is its support for RTX IO, an GPU-accelerated decompression scheme running on Vulkan. RTX IO, similar to Direct Storage 1.2 in Ratchet and Clank: Rift Apart, aims to improve game loading and asset streaming on the PC platform. This provides an excellent opportunity to explore the capabilities of this technology.
Improving Game Loading and Asset Streaming
Traditionally, game loading involved transferring data from a hard drive to system memory and then to the GPU under the control of the CPU. However, this method was latency-heavy and sequential, requiring the disk to spin up, locate the data, and load it block by block while minimizing seeking.
With games becoming larger, often hundreds of gigabytes in size, and featuring highly detailed assets, data compression has become essential to utilize storage space and bandwidth effectively. However, decompressing data on the CPU adds extra time and burden.
Luckily, the introduction of rapid, low-latency flash storage in SSDs brings new possibilities. The aim is to access data in parallel, reducing load times compared to traditional methods, and move the data from storage to the GPU for decompression, which GPUs handle better than CPUs. This streamlined approach, implemented in RTX IO and Direct Storage 1.2, leads to faster loading times and potential performance improvements by reducing the CPU load.
In the case of RTX IO, data on disk is compressed using the GDeflate format, temporarily moved to system memory, and then to VRAM for decompression by the GPU. This compression format, an open standard from Nvidia, is expected to be used in Direct Storage 1.2 games on PC with support from Nvidia, AMD, and Intel GPUs.
RTX IO in Portal Prelude RTX
Portal Prelude RTX utilizes the Vulkan graphics API, which currently lacks vendor-agnostic standard calls for GPU decompression. Only Nvidia’s proposed extensions currently support GPU decompression. These extensions may potentially be adopted by the Kronos group for Vulkan’s Direct Storage Equivalent.
Although Portal Prelude RTX operates on a traditional loading paradigm, RTX IO still offers benefits in terms of dedicated load times and visible texture load times. It doesn’t significantly impact frame rates or replace the game engine but enhances rendering and asset loading methods.
To gauge the effect of RTX IO in Portal Prelude RTX, tests were conducted in different configurations. Results revealed that a 500MB/s SATA drive with RTX IO enabled outperformed a 3.5GB/s NVMe drive without RTX IO. Moreover, hardware variations in CPU and GPU did not significantly impact loading times, indicating that this technology is not highly dependent on specific hardware configurations.
While Portal Prelude RTX demonstrates the promising potential of this technology on PC, its impact will be more pronounced in games with active streaming and no loading screens, such as Ratchet and Clank: Rift Apart. We look forward to covering the upcoming release of Ratchet and Clank: Rift Apart on PC on July 26th to see this technology in action. Stay tuned!