[docs] initial user handbook draft

Signed-off-by: lizzie <lizzie@eden-emu.dev>

docs/README.md

@@ -7,4 +7,4 @@ This contains documentation created by developers. This contains build instructi
 - **[Dependencies](Deps.md)**
 - **[CPM - CMake Package Manager](CPMUtil.md)**
 - **[Platform-Specific Caveats](Caveats.md)**
-- **[User Directory Handling](User.md)**
+- **[User Handbook](User.md)**

docs/User.md

@@ -1,11 +1,6 @@
-# User configuration
+# User handbook
 
-## Configuration directories
+This handbook is primarily aimed at the end-user - baking useful knowledge for enhancing their emulation experience.
 
-Eden will store configuration in the following directories:
-
-- **Windows**: `%AppData%\Roaming`.
-- **Android**: Data is stored internally.
-- **Linux, macOS, FreeBSD, Solaris, OpenBSD**: `$XDG_DATA_HOME`, `$XDG_CACHE_HOME`, `$XDG_CONFIG_HOME`.
-
-If a `user` directory is present in the current working directory, that will override all global configuration directories and the emulator will use that instead.
+- **[The Basics](docs/Basics.md)**
+- **[Graphics](user/Graphics.md)**

docs/user/Basics.md

@@ -0,0 +1,47 @@
+# User Handbook - The Basics
+
+## Introduction
+
+Eden is a very complicated piece of software, and as such there are many knobs and toggles that can be configured. Most of these are invisible to normal users, however power users may be able to leverage them to their advantage.
+
+This handbook primarily describes such knobs and toggles. Normal configuration options are described within the emulator itself and will not be covered in detail.
+
+## User configuration
+
+### Configuration directories
+
+Eden will store configuration files in the following directories:
+
+- **Windows**: `%AppData%\Roaming`.
+- **Android**: Data is stored internally.
+- **Linux, macOS, FreeBSD, Solaris, OpenBSD**: `$XDG_DATA_HOME`, `$XDG_CACHE_HOME`, `$XDG_CONFIG_HOME`.
+
+If a `user` directory is present in the current working directory, that will override all global configuration directories and the emulator will use that instead.
+
+### Environment variables
+
+Throughout the handbook, environment variables are mentioned. These are often either global (system wide) or local (set in a script, bound only to the current session). It's heavily recommended to use them in a local context only, as this allows to rollback changes easily (if for example, there are regressions setting them).
+
+The recommended way is to create a `.bat` file alongside the emulator `.exe`; contents of which could resemble something like:
+
+```bat
+set "__GL_THREADED_OPTIMIZATIONS=1"
+set "SOME_OTHER_VAR=1"
+eden.exe
+```
+
+Android doesn't have a convenient way to set environment variables.
+
+For other platforms, the recommended method is using a bash script:
+
+```sh
+export __GL_THREADED_OPTIMIZATIONS=1
+export SOME_OTHER_VAR=1
+./eden
+```
+
+Then just running `chmod +x script.sh && source script.sh`.
+
+## Compatibility list
+
+Eden doesn't mantain a compatibility list. However, [EmuReady](https://www.emuready.com/) has a more fine-grained compatibility information for multiple emulators/forks as well.

docs/user/Graphics.md

@@ -0,0 +1,45 @@
+# User Handbook - Graphics
+
+## Visual Enhancements
+
+### Anti-aliasing
+
+Enhancements aimed at removing jagged lines/sharp edges and/or masking artifacts.
+
+- **No AA**: Default, provides no anti-aliasing.
+- **FXAA**: Fast Anti-Aliasing, an implementation as described on [this blog post](https://web.archive.org/web/20110831051323/http://timothylottes.blogspot.com/2011/03/nvidia-fxaa.html). Generally fast but with some innocuos artifacts.
+- **SMAA**: Subpixel Morphological Anti-Aliasing, an implementation as described on [this article](https://web.archive.org/web/20250000000000*/https://www.iryoku.com/smaa/).
+
+### Filters
+
+Various graphical filters exist - each of them aimed at a specific target/image quality preset.
+
+- **Nearest**: Provides no filtering - useful for debugging.
+- **Bilinear**: Provides the hardware default filtering of the Tegra X1.
+- **Bicubic**: Provides a bicubic interpolation using a Catmull-Rom (or hardware-accelerated) implementation.
+- **Zero-Tangent, B-Spline, Mitchell**: Provides bicubic interpolation using the respective matrix weights. They're normally not hardware accelerated unless the device supports the `VK_QCOM_filter_cubic_weights` extension. The matrix weights are those matching [the specification itself](https://registry.khronos.org/vulkan/specs/latest/html/vkspec.html#VkSamplerCubicWeightsCreateInfoQCOM).
+- **Spline-1**: Bicubic interpolation (similar to Mitchell) but with a faster texel fetch method. Generally less blurry than bicubic.
+- **Gaussian**: Whole-area blur, an applied gaussian blur is done to the entire frame.
+- **Lanczos**: An implementation using `a = 3` (49 texel fetches). Provides sharper edges but blurrier artifacts.
+- **ScaleForce**: Experimental texture upscale method, see [ScaleFish](https://github.com/BreadFish64/ScaleFish).
+- **FSR**: Uses AMD FidelityFX Super Resolution to enhance image quality.
+- **Area**: Area interpolation (high kernel count).
+- **MMPX**: Nearest-neighbour filter aimed at providing higher pixel-art quality.
+
+### External
+
+While stock shaders offer a basic subset of options for most users, programs such as [ReShade](https://github.com/crosire/reshade) offer a more flexible experience.
+
+## Driver specifics
+
+### Mesa environment variable hacks
+
+The software requires a certain version of Vulkan and a certain version of OpenGL to work - otherwise it will refuse to load, this can be easily bypassed by setting an environment variable: `MESA_GL_VERSION_OVERRIDE=4.6 MESA_GLSL_VERSION_OVERRIDE=460` (OpenGL) and `MESA_VK_VERSION_OVERRIDE=1.3` (Vulkan), for more information see [Environment variables for Mesa](https://web.archive.org/web/20250000000000*/https://docs.mesa3d.org/envvars.html).
+
+### NVIDIA OpenGL environment variables
+
+Unstable multithreaded optimisations are offered by the stock proprietary NVIDIA driver on X11 platforms. Setting `__GL_THREADED_OPTIMIZATIONS` to `1` would enable such optimisations. This mainly benefits the OpenGL backend. For more information see [Environment Variables for X11 NVIDIA](https://web.archive.org/web/20250115162518/https://download.nvidia.com/XFree86/Linux-x86_64/435.17/README/openglenvvariables.html).
+
+### swrast/LLVMpipe crashes under high load
+
+The OpenGL backend would invoke behaviour that would result in swarst/LLVMpipe writing an invalid SSA IR (on old versions of Mesa), and then proceeding to crash. The solution is using a script found in [tools/llvmpipe-run.sh](../../tools/llvmpipe-run.sh).