I noticed Ogre 2.1’s release announcement atracted more popularity than I expected (thank you!!!) thus I shall explain:
Ogre 2.1 has been in development for many years, approximately since 2015.
At some point it matured and we started working on the next version: Ogre 2.2
Our regular users who stick around knew 2.1 has been stable for a while now; but we just didn’t have the time or resources to make a release (packaging binaries, ensuring everything works, etc). And many fixes from 2.2 also kept getting backported.
And 2.2 had just reached maturity too.
Ogre 2.1 was a major refactor and users porting existing code from Ogre 1.x is definitely doable, but still requires a lot of effort.
Unlike 1.x -> 2.1 transition though, 2.1 -> 2.2 transition is a much smoother experience, because it mostly touches Texture manipulation code and end users rarely manipulate a lot of Textures via code directly.
The Texture code of 2.1 was entirely replaced by the new TextureGpu code; which supports background streaming and solves many RAM issues that plagued 2.2.
Wait! 2.2.1… where’s Ogre 2.2.0?
Ogre 2.2.1 and 2.2.0 are being released concurrently. This is because during development a few of our users and testers needed to distinguish between more stable features (texture streaming) from the less stable ones (Global Illumination) and we used OGRE_VERSION_PATCH for that.
However our GI code has stabilized now.
Because there is now virtually no reason to use Ogre 2.2.0 over 2.2.1; we just went ahead and make a source-code-only release of Ogre 2.2.0 for archival reasons and a source-code + SDK release of 2.2.1
Ogre 2.2.1 also contained several bug fixes which made no sense to backport to 2.2.0 as it would only increase our work.
Texture streaming! Completely refactored Texture code. It consumes a lot less RAM and supports background streaming
Voxel Cone Tracing (VCT): Semi-Realtime GI solution. Supports diffuse and specular. Can consume a lot of VRAM depending on quality. Lighting changes can be done in realtime. Changes to static objects in scene needs to rebuild voxels (not realtime)
Irradiance Field with Depth (IFD): Generic variant of DDGI using Voxels (consumes more VRAM) or Rasterization (slower to build). It supports diffuse only and is lower quality than VCT, but is much faster. And if completely static, consumes very little memory.
Per-pixel Cubemap probes
VR readiness: New sample showing how to integrate OpenVR SDK, deal with running start, performance optimizations such as Instanced Stereo, Hidden Area Mesh and Radial Density Mask
Mobile friendly: Added Load and Store actions to control how TBDR GPUs flush their caches
Stable PSSM Shadowmaps
All branches except the Vulkan one are being merged back into master. Whatever is in master will likely become Ogre 2.2.2 one day.
That doesn’t mean Vulkan will or will not make it to 2.2.2, it’s just that we want to always keep master branch with a relatively high degree of stability (i.e. rolling release model), which the Vulkan branch cannot yet provide.
Refactored Ogre 1.x to increase performance by several factors; using cache friendly techniques (Data Oriented Design), SIMD instructions, AZDO (Aproaching Zero Driver Overhead), auto instancing, and multithreading
Windows Vista/7/8/10 support, macOS via Metal and OpenGL, iOS via Metal, Linux via OpenGL
Many new features: Area lights, Parallax Corrected Cubemaps, Forward Clustered lights, HDR, Exponential Shadowmaps and more
In many of the samples this is not a problem because they perform a full stall for demo purposes, but some of the more ‘real world’ samples do not.
They also do not teach how to deal with GPU systems where the present queue and the graphics rendering queue are different (I don’t know which systems have this setup, but I suspect it has to do with Optimus laptops and similar setups where GPU doing rendering is not the one hooked to the monitor).
This bug is hard to catch because often the race condition will never happen due to the nature of double and triple buffer, and worst case scenario this could result in tearing or similar artifacts (even if vsync is enabled).
Though there’s the possibility that failing to insert this barrier can result in severe artifacts in AMD GPUs due to DCC compression on render targets being dirty while rendering to it. Godot’s renderer had encountered this problem.
Once you get into the async mindset, Vulkan makes sense.
Where to next?
There’s a lot that needs to be done: Resizing the swapchain is not yet coded, separate Graphics and Present queues is not handled, there’s zero buffer management, no textures, no shaders.
The next task I’ll be focusing on is shaders; because they are useful to show stuff on screen and see if they’re working. Even if there are no vertex buffers yet, we can use gl_VertexID tricks to render triangles on screen.
And once shaders are working, we can then test if vertex buffers work once they’re ready, and if textures work, etc.