168 lines
12 KiB
Markdown
168 lines
12 KiB
Markdown
+++
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date = "2016-04-19T12:12:00-05:00"
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title = "Citra Progress Report - 2016 P1"
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tags = [ "progress-report" ]
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author = "jmc47"
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forum = 37
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+++
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Welcome to the first Citra Progress Report of 2016! While 2015 will be considered the year that Citra first played
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games, 2016 is quickly shaping up as a year filled with higher compatibility, greater stability and much more as Citra
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matures. The avalanche of new features from tons of contributors has made it hard to keep up with everything even for
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developers!
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Because there have been so many changes and there are so many different games, it can be very hard to keep up with what
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is working and what is not. To try and make things a little easier, we've compiled some of the biggest changes of the
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new year together to show you just how far Citra has come already!
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## [Immediate Mode Vertex Submission Part 1](https://github.com/citra-emu/citra/pull/1394) and [Part 2](https://github.com/citra-emu/citra/pull/1461) by [ds84182](https://github.com/ds84182) & [yuriks](https://github.com/yuriks)
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Immediate Mode Vertex Submission is a second way for the PICA200 (aka the 3DS GPU) to draw vertices. Unlike the normal
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method, Immediate Mode trades off some efficiency when drawing complex models for less overhead on each object. This
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makes it a suitable option for things such as UI elements. Despite all of that, it's capable of being used for just
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about anything, and some games use it for drawing all of their graphics.
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[ds84182](https://github.com/ds84182) first implemented the feature and showed just how many games it could fix. After
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it was merged, some issues were found and [yuriks](https://github.com/yuriks) fixed some edge cases and added support
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for *vertex restart*. Vertex Restart is a feature necessary when drawing using triangle strips, in order to break apart
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consecutive strips.
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{{< figure src="/images/entry/citra-progress-report-2016-p1/etrianodysseytop.png"
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alt="Etrian Odyssey IV"
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title="Etrian Odyssey IV running in Citra with Immediate Mode Vertex Submission" >}}
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With this, along with previous fixes of [#1462](https://github.com/citra-emu/citra/pull/1462) and
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[#1624](https://github.com/citra-emu/citra/pull/1624) for correct depth writing behaviors, Etrian Odyssey IV and other
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games appear to be playable in Citra.
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## [Unicode Support on Windows](https://github.com/citra-emu/citra/pull/1541) by [LFsWang](https://github.com/LFsWang)
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Due to the different way Windows reports filenames to programs compared to Linux or OS X, Citra was previously unable
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to load any files with a path containing non-English characters. That is, if your file was named using accented
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letters, Chinese, Japanese characters, emoji, or in general any characters not present in the
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[ASCII](https://en.wikipedia.org/wiki/ASCII) character set, Citra would be unable to find the file! Considering Citra
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is developed and used by people around the world, this was a very important issue. We did not want people to need to
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rename files or directories to be able to open them with Citra.
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[LFsWang](https://github.com/LFsWang) took the time to fix the frontend code so that Citra was able to correctly load
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these files. [More recently](https://github.com/citra-emu/citra/pull/1620) further improvements were made so that this
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works correctly even if you're loading files with characters from a language different than the one running on your
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operating system.
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## [Fix MAD/MADI Shader Instruction Encoding](https://github.com/citra-emu/citra/pull/1479) by [JayFoxRox](https://github.com/JayFoxRox)
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MAD and MADI (Multiply-Add and Multiply-Add Inverted, respectively.) are shader instructions in the PICA200 GPU, handled
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by Citra's shader JIT and interpreter. These instructions execute a multiplication followed by an addition
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(*d* = *a* × *b* + *c*) in the same instruction. They're unique in that they're the only instructions that works with
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3 source operands, and thus have a special way of being encoded into the program. Citra interpreted this format
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incorrectly, causing it to sometimes operate on the wrong values!
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Handling these instructions correctly, much like a CPU emulator, is paramount for accurate emulation. In this case, it
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happened that these instructions were commonly used in font rendering shaders, and this bug often manifested as
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gibberish textures and incorrect positioning, as can be seen in this The Legend of Zelda: A Link Between Worlds
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screenshot:
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{{< figure src="/images/entry/citra-progress-report-2016-p1/albwbefore.png" >}}
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{{< figure src="/images/entry/citra-progress-report-2016-p1/albwafter.jpg"
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title="The Hylian language just seems to get harder and harder to read every game! Oh... wait." >}}
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Considering that emulators over a decade older than Citra are still finding problems with how CPU instructions are
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handled, it's no surprise that our shaders aren't bullet-proof yet either. There should be many, many games affected
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by the encoding fixes, so if you've been seeing gibberish text or other problems, there's a fair chance that this
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change could have fixed the bug.
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## [Align Attribute Components](https://github.com/citra-emu/citra/pull/1496) by [JayFoxRox](https://github.com/JayFoxRox)
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Vertex Attributes are an integral step in rendering. They can tell the GPU the bone weight, color, position, etc. So
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when [JayFoxRox](http://github.com/JayFoxRox) discovered that the Vertex Attributes were misaligned and pulling the
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incorrect values, he knew he stumbled upon a major problem. One game in particular affected by this was Super Smash
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Bros. 4, which since the MAD/MADI fixes had been displaying some graphics, although things looked pretty messed up.
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{{< figure src="/images/entry/citra-progress-report-2016-p1/smashbrosbefore.jpg"
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title="Pikachu has seen better days." >}}
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{{< figure src="/images/entry/citra-progress-report-2016-p1/smashbrosafter.png"
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title="While lighting is a bit off, the game looks fairly playable!" >}}
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With this fix, the Super Smash Bros. 4 actually looks fairly playable! The align attributes fixes should also fix other
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games where the graphics tend to explode like Super Smash Bros. 4.
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## [Save Fixes](https://github.com/citra-emu/citra/pull/1302) by [Subv](https://github.com/Subv)
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One of the more notable problems that Citra has currently is that many games require a savefile extracted from the 3DS
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in order to get in game. This is due to many reasons, including partial or incorrect file system and OS emulation.
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Because getting saves from newer games can be problematic due to encryption (and it's generally a pain anyway), getting
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Citra to create and load savegames properly is a very important task that will continue to be a priority for the
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forseeable future.
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The save fixes recently merged mostly have to do with formatting the cartridge saves correctly. 3DS titles are very
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picky about how their saves are formatted and will often fail if all of the files aren't handled *exactly* like they
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want. This was the reason why Mario Kart 7 would hang in Citra! And once you're in game, it is quite the visual treat
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for a 3DS title!
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{{< figure src="/images/entry/citra-progress-report-2016-p1/mk7.jpg"
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title="Mario Kart 7 is now fully playable in Citra and looking better than ever!" >}}
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The above change fixes Mario Kart 7, Final Fantasy Explorers, Lego Batman 3: Beyond Gotham, The Amazing Spiderman, and
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likely many others games that previously hung while creating or deleting savefiles.
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## [Clear Shader JIT Cache](https://github.com/citra-emu/citra/pull/1503) by [bunnei](https://github.com/bunnei)
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Citra's GPU shader JIT had a bit of a flaw: It would keep previously compiled shaders in memory forever. Furthermore,
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it only allocated a fixed amount of space for all compiled shader code. When testing the early games that booted on
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Citra, none of this seemed to matter and things continued fine. But, as Citra has been running more complex games and
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was being used by more users for longer periods of time, it became apparent that this simply wasn't good enough. Games
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were managing to fill up the fixed amount of space that Citra had allocated for the Shader JIT Cache and crashing the
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emulator!
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[bunnei](https://github.com/bunnei) added a simple fix to the memory management which allows Citra to drop old, unused
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shaders in order to free up space for new ones being requested by the game, fixing these crashes and allowing for
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longer game sessions. For example, Kirby: Triple Deluxe is now stable in Citra, even when using the Shader JIT:
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{{< figure src="/images/entry/citra-progress-report-2016-p1/b.png" >}}
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{{< figure src="/images/entry/citra-progress-report-2016-p1/c.png"
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title="Kirby: Triple Deluxe used to crash almost immediately while in game" >}}
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## [Shader JIT Refactor](https://github.com/citra-emu/citra/pull/1546) by [bunnei](https://github.com/bunnei)
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While most of the issues with the shader JIT were fixed with the aforemoentioned changes, there remained a fundamental
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flaw with how flow control was handled. Previously, the shader JIT inlined CALL and JMP instructions. This had several
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issues: 1) Inlining all subroutines resulted in bloated shaders being generated, and 2) jumping to arbitrary addresses
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(and nested jumps) couldn't be supported. This is because when inlining code, the same source shader code might be
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recompiled multiple times. To support arbitrary jumps, there needed to be a one-to-one mapping of source code to
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compiled code.
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To fix this, [bunnei](https://github.com/bunnei) refactored the shader JIT to do a multiple step compile: First,
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analyze the shader and identify subroutines, jumps, and return locations. Next, compile the code (just once), and
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insert additional code to handle the returns and jumps. In addition to enabling arbitrary CALL/JMP instructions, this
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results in pretty constant compiled shader sizes of around 40kb, which significantly reduced the memory footprint of
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the shader JIT.
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This change fixes IronFall: Invasion, Pokemon: Rumble Blast, and several other games:
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{{< figure src="/images/entry/citra-progress-report-2016-p1/1.png" >}}
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{{< figure src="/images/entry/citra-progress-report-2016-p1/2.png"
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title="With these changes, all known graphical glitches with IronFall: Invasion are fixed in Citra" >}}
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## [Audio Framework](https://github.com/citra-emu/citra/pull/1386) by [MerryMage](https://github.com/merrymage)
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We'd like to mention the amazing work done by [MerryMage](https://github.com/merrymage) to bring proper DSP HLE and
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audio support to Citra. Over the past few months, she has been carefully chipping away at figuring out how audio 3DS
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works, removing several hacks in Citra along the way. While many of her efforts have been transparent to users up
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until this point, they have laid the groundwork for soon-to-come audio support. With changes
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[#1386](https://github.com/citra-emu/citra/pull/1386), [#1403](https://github.com/citra-emu/citra/pull/1403),
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[#1441](https://github.com/citra-emu/citra/pull/1441), [#1566](https://github.com/citra-emu/citra/pull/1566), and
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[#1572](https://github.com/citra-emu/citra/pull/1572), we're now closer than ever to hearing games for the first time
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in Citra! While [MerryMage](http://github.com/merrymage) has audio nearly complete in unofficial branches, there are
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still a few remaining issues before it gets merged.
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## Contributors of 2016
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We've got a fortunate problem to have: It's often too difficult to mention every contribution made to Citra when
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writing progress reports! We'd like to extend a special thanks
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[to all that helped advance Citra further](https://github.com/citra-emu/citra/graphs/contributors?from=2016-01-01&to=2016-04-19&type=c)
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since our last progress report, you guys rock!
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