Libretro A crossplatform application API, powering the crossplatform gaming platform Retro. Arch. I needed a break from para. LLEl RDP, and I wanted to give PSX a shot to have an excuse to write a higher level Vulkan renderer backend. The renderer backends in Beetle PSX are quite well abstracted away, so plugging in my own renderer was a trivial task. The original Play. Station is certainly a massively simpler architecture than N6. After one evening of studying the Rustation renderer by simias and PSX GPU docs, I had a decent idea of how it worked. Wii U Overscan Patch' title='Wii U Overscan Patch' />Many hardware features of the N6. Perspective correctness no W from GTETexture filtering. Sub pixel precision on vertices wobbly polygons, weeMipmapping. No programmable texture cache. Depth buffering. Complex combiners. My goal was to create a very accurate HW renderer which supports internal upscaling. Making anything at native res for PSX is a waste of time as software renderers are basically perfected at this point in Mednafen and more than fast enough due to the simplicity. Another goal was to improve my experience with 2. D heavy games like the Square RPGs which heavily mix 2. D elements with 3. D. I always had issues with upscaling plugins back in the day as I always had to accept blocky and ugly 2. D in order to get crisp 3. D. Simply sampling all textures with bilinear is one approach, but it falls completely flat on PSX. Content was not designed with this in mind at all, and youll quickly find that tons of artifacts are created when the bilinear filtering tries to filter outside its designated blocks in VRAM. The final goal is to do all of this without ugly hacks, game specific workarounds or otherwise shitty code. It was excusable in a time where graphics APIs could not cleanly express what emulation authors wanted to express, but now we can. Development of this renderer was a fairly smooth ride, mostly done in spare time over 2 months. Credits. This renderer would not exist without the excellent Mednafen emulator and Rustation GL renderer. Tested hardwaredriversn. Vidia LinuxWindows 3. AMDGPU PRO 1. 6. Linux works fullyMesa Intel Ivy Bridge half way working, Broadwell, fully working, youll want to build from Git to get some important bug fixes which were uncovered by this renderer DMesa Radeon RADV fully working, youll want to build from Git to get support for input attachments But, but, I dont have a Vulkan capable GPUWell, read on anyways, some of this work will benefit the GL renderer as well. But, but, youre stupid, you should do this in GL 1. No Fine, but clearly this is just for shits and giggles. Doing it for the lulz is always a valid reason. Source. The source will be merged upstream to Github immediately. PSX GPU overview. The PSX GPU is a very simple and dumb triangle rasterizer with some tricks. VRAMThe PSX has a 1. Wii U Overscan Patch' title='Wii U Overscan Patch' />VRAM at 1. MB of VRAM to work with. Interestingly enough, this VRAM is actually organized as a 2. D grid, and not a flat array with widthheightstride. This certainly simplifies things a lot as we can now represent the VRAM as a texture instead of shuffling data in and out of SSBOs. Unlike N6. 4, the CPU doesnt have direct access to this VRAM phew, so access is mediated by various commands. Wii U Overscan Patch' title='Wii U Overscan Patch' />Terremoto. Terremoto scossa magnitudo 4 vicino Amatrice, epicentro a 3 kmTerremoto oggi Lazio 4 dicembre 2017, scossa M 4. Amatrice. The libretro API has been enhanced by David Walters in the following ways Button input was previously alldigital, now button input can be analog as well. Textures. The PSX can sample textures at 4 bit palettes, 8 bit palettes or straight ABGR1. Texture coordinates are confined to a texture window, which is basically an elaborate way to implement texture repeats. Textures are sampled directly from VRAM, but there is a small texture cache. For purposes of emulation, this cache is ignored except for one particular case which well get to. An annoying feature is that the color 0x. PSX is always transparent, so all fragment shaders which sample textures might have to discard, another reason to be careful with bilinear. Shading options. PSX just has 3 shading options, which makes our life very simple Interpolate color from vertices. Wii U Overscan Patch' title='Wii U Overscan Patch' />Information on running Star Wars Episode I Racer on modern PCs. The Samsung JU7100 is a great 4k LED TV. With the exception of the discoloration it gets when viewed at an angle, it has impressive picture quality. It is also a. Interpolate UV and sample nearest neighbor. Sample texture multiplied by interpolated color gouraud shadingIt is practical to not use uber shading approaches here. Freedom Scientific Magic 11 Crack here. Semi transparency. PSX has a weird way of dealing with transparency. There is no real alpha channel to speak of, we only have one bit, so what PSX does is set a constant transparency formula, A B, 0. A 0. 5. B, B A, or 0. A B. If the high bit of a texture color is set, transparency is enabled, if not, the fragment is considered opaque. Semi transparent color only primitives are simply always transparent. Mask bit. Possibly the most difficult feature of the PSX GPU is the mask bit. The alpha bit in VRAM is considered a read only bit if mask bit testing is enabled and the read only bit is set. This affects rendering primitives as well as copies from CPU and VRAM to VRAM blits. Especially mask bit emulation semi transparency creates a really difficult blending scenario which I havent found a way to do correctly with fixed function but that wont stop us in Vulkan. Correctly emulating mask bit lets us render Silent Hill correctly. The trees have transparent quads around them without it. Intersecting VRAM blits. It is possible, and apparently, well defined on PSX to blit from one part of VRAM to another part where the rects intersect. Reading the MednafenBeetle software implementation, we need to kind of emulate the texture cache. Fortunately, this was very doable with compute shaders, although not very efficient. Implementation details. Feature Adaptive smoothing. As mentioned, I prefer smooth 2. D with crisp looking 3. D. I devised a scheme to do this in post. The basic idea is to look at our 4x or 8x scaled image, we then mip map that down to 1x with a box filter. While mip mapping, we analyze the variance within the 44 or 88 block and stick that in alpha. The assumption here is that if we have nearest neighbor scaled 2. D elements, they typically have a 1 1 pixel correspondency in native resolution, and hence, the variance within the block will be 0. With 3. D elements, there will be some kind of variance, either by values which were shaded slightly differently, or more dramatically, a geometry edge. We now compute an R8UNORM bias mask texture at 1x scale, which is 0. D elements, and 1. D. To avoid sharp transitions in LOD, the bias mask is then blurred slightly with a 33 gaussian kernel might be a better non linear filter here for all I know. On final scanout we simply sample the bias mask, multiply that by log. Lod with trilinear sampling, and magically 2. D elements look smooth without compromising the 3. D sharpness. Sure, its not perfect, but Im quite happy with the result. Consider this scene from FF IX. While some will prefer this look its toggleable, Im not a big fan of blocky nearest neighbor backgrounds together with high res models. With adaptive smoothing, we can smooth out the background and speech bubble back to native resolution where they belong. You may notice that the shadow under Vivi is sharp, because the shadow which modulates the background is not 1 1. This is the downside of doing it in post certainly, but its hard to notice unless youre really looking. The bias mask texture looks like this after the blur Potential further ideas here would be to use the bias mask as a lerp between x. BR style upscalers if we wanted to actually make the GPU not fall asleep. There is nothing inherently Vulkan specific about this method, so it will possibly arrive in the GL backend at some point as well.