Just after some days after the relaunch of the GPUOpen program that featured new toolkits and an expanded FidelityFX suite, AMD also released the 4.0 version of Radeon Rays. \n \nThe ray intersection acceleration library – formerly known as FireRays— happens to be part of the AMD ProRender software pack. \n \nPreviously it could work on the CPU, which happened to be the limitation. With the recent RDNA2 AMD GPUs that have been confirmed to create hardware support for ray tracing, Radeon Rays 4.0 now has BVH optimization mainly for GPU access and also one of the powerful low-level APIs: Apple's Metal, Khronos’ Vulkan, and Microsoft’s DirectX 12. \n \nThere is also support for Heterogeneous-Compute Interface for Portability (HIP), which happens to be AMD's C++ parallel computing platform, similar to NVIDIA's CUDA. \n \n \n \nFeatures to look out for in Radeon Rays 4.0 \n \nCustom AABB \nThis feature’s purpose is to guide the construction of the Bounding Volume Hierarchy (BVH) by bringing a custom AABB hierarchy for your scene. \n \nGPU BVH Optimization \nThis feature optimizes the Bounding Volume Hierarchy (BVH), mainly built for efficient GPU access. \n \nNew APIs \nThis feature helps in selecting several different API endpoints to ensure Radeon Rays 4.0 integrates seamlessly with the existing application. \n \nThe recent release now drops support for Open CL, but most importantly, the Radeon Rays 4.0 release is not open-source, unlike others. \n \nAfter having received complaints from several users, AMD took necessary action in reversing their decision. As a result, Brain Savery, Product Manager for ProRender, wrote the following message on the AMD subreddit: \n \nFollowing the complaints of several users, AMD decided to reverse this decision partially. Here's what Brian Savery, Product Manager for ProRender, wrote the following message on the AMD subreddit: \n \nWe have reviewed this internally and will be making the following changes: AMD will make Radeon Rays 4.0 open source. However, specific AMD IP will be placed into libraries and have source code available for the community via SLA. \n \nAs u\/scottherkleman mentioned in the thread about the (amazing looking) Unreal 5 demo, we are committed to providing common ray tracing libraries, not locked down to a single vendor. This is the entire point of Radeon Rays, and while offering standard libraries with a permissive license is valid, based on your feedback, we can improve that offering with source code. \n \nPlease keep building awesome things with Radeon Rays, and if you are the type of developer who needs source code to edit immediately, please get in touch through the Github page or GPUOpen. Also, the source for 2.0 can be found on GPUOpen for GitHub. \n \nThis can be regarded as good news for those looking to switch to Radeon Rays, mostly when AMD ProRender is now official with a free import plugin for Unreal Engine.