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Main - Compatibility / Testing - Desmume comparison/image differences (Phoenix Wright: Ace Attorney) New reply


Niklink
Posted on 02-14-18 08:57 PM (rev. 2 of 02-14-18 10:39 PM) Link | #534
So I was taking screenshots of AA1 for unrelated reasons on both Desmume and melonDS when I noticed a slight difference between the image presented on each one. So I went ahead and took an identical screenshot from each to point out what I mean. It's subtle, but it's there:

[image]

In case you don't want to squint too much, there are two differences between the images. The first and most obvious is the difference in transparency. You can see the background behind the dialogue arrow box in the bottom screen more easily on Desmume. The image diff also appears to show a similar thing happening with the text box on the upper screen. Simply put, it appears that there is a difference with how transparency is handled. The second, more subtle difference is that the image in Desmume is apparently producing a slightly brigter image overall that melonDS (fun fact: the screenshot feature in Desmume turns images darker instead, which almost had me writing the opposite thing until I thought to check manually). The difference is quite small, usually somewhere between 010101 and 030303's worth of additional brightness on any given color.

So, two troubling differences given that one emulator is aiming for a higher degree of accuracy and the other has had years to ensure precision. At this point I went and grabbed my 3DS to try to get a real hardware comparison. Unfortunately I have no way of getting screenshots of DS games so I just had to make do with squinting. As far as I can tell, the transparency issue on the bottom screen looks much more like melonDS than it does Desmume, but I can't be authoritative about it. And the brightness issue, I have no way of telling given the differences between a 3DS screen and a computer monitor. In any case, given that melonDS' 2D graphics are supposed to be well underway, something to think about. Which emulator is in the wrong here? And why?

PSISP
Posted on 02-14-18 10:07 PM Link | #535
While there's no way to confirm this until it's been verified on hardware, I would guess that melonDS is correct. StapleButter has put effort into making the 2D renderer pixel-perfect and basically doing things right from the start. Compare that with DeSmuME, whose main priority, starting a decade ago, was getting games to boot without much consideration towards some of the finer details of the GPU.

StapleButter
Posted on 02-15-18 06:48 AM (rev. 2 of 02-15-18 06:48 AM) Link | #536
melonDS renders in 18-bit color, akin to the DS. (this makes 2D colors appear slightly dimmer because the hardware is sloppy about it)

DeSmuME... not too sure. The code shows it's able to render in 15-bit, 18-bit and 24-bit colors, but it seems the choice is only exposed to Mac users? Here on Windows it seems to render in 15-bit color.

Anyway, the use of 15-bit color results in slightly less good blending/fade effects.

This doesn't exclude that melonDS might be wrong somewhere tho, I never checked the blending effects against hardware.

____________________
Kuribo64


Main - Compatibility / Testing - Desmume comparison/image differences (Phoenix Wright: Ace Attorney) New reply

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