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Thoughts on Direct3D Vs. Overlay (and other output options)

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First post, by lukeman3000

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Let me preface this by saying I know virtually nothing about the technical aspects behind these different output options; I'm only interested it from a standpoint of "what looks better" and what's more "true" to the original game.

So, I've been using overlay with the normal3x scaler for all of my DOSBox games such as Space Quest, King's Quest, etc. It has been my impression that overlay used with a normal2x or normal3x scaler presents the most "accurate" (nice and blocky) representation of the game.

However, recently I have discovered the awesomeness of SVN builds, and I have started using Taewoong's DOSBox DAUM SVN build. I love it mainly because of save states (I don't have time to set down and play through the entirety of Prince of Persia 2), but I have also found that it offers a couple of new output options, such as Direct3D.

I took some screenshots of Direct3D and overlay (with normal3x) to compare and contrast. In general, Direct3D seems to actually be a little sharper and clearer in some instances (certain areas of the screen looked like they got a little less blurry with Direct3D), but the color palette seems to be slightly different, as well. Another thing I noticed is that when using Direct3D, it kind of looks like something happens down the middle of the screen, but it's hard to tell what. It doesn't look bad, necessarily, just different.

What I'm wondering is, what are the pros and cons to using Direct3D Vs. Overlay? If I had to pick one based on the sharpness of the image, I would have to go with Direct3D. It seems to look pretty nice to me. But I'm also slightly concerned about the altered color palette and perhaps other graphical artifacts that seem to be present (the line down the middle of the screen thing). For your comparison, I have taken a couple screenshots from SQ3. I'd recommend setting it up so that you can quickly switch back and forth between the two to see the differences:

Overlay with Normal3x scaler

Direct3D

Reply 1 of 3, by VileR

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The way output methods work depend on your OS, hardware, and drivers, so it's not always easy to tell which one would be optimal. In this case the palette in the direct3d screenshot looks to be correct... the overlay one is slightly off, but due to the jpeg artifacts it's not really clear just how.
Both shots have the characteristic uneven pixel dimensions that come with sharp non-integer scaling, though the overlay one adds some odd slight blur on top of that for whatever reason. I'm almost positive that both of these effects in overlay mode are due to some setting in your gpu's control panel.

Anyway, if you're already trying out direct3d, check out the pixelshaders - that's what it's for. ;)

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Reply 2 of 3, by gulikoza

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Overlay will always have slightly different colors because of RGB->YUV conversion.
What line down the middle of the screen?

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Reply 3 of 3, by lukeman3000

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VileRancour wrote:

The way output methods work depend on your OS, hardware, and drivers, so it's not always easy to tell which one would be optimal. In this case the palette in the direct3d screenshot looks to be correct... the overlay one is slightly off, but due to the jpeg artifacts it's not really clear just how.
Both shots have the characteristic uneven pixel dimensions that come with sharp non-integer scaling, though the overlay one adds some odd slight blur on top of that for whatever reason. I'm almost positive that both of these effects in overlay mode are due to some setting in your gpu's control panel.

Anyway, if you're already trying out direct3d, check out the pixelshaders - that's what it's for. 😉

You think that blur is being caused by a setting in my GPU control panel? I'm running this on a Samsung laptop with integrated HD 4000 graphics.. I wonder what setting would possibly be doing that? And what you're saying is that overlay with normal3x should look just as clear and sharp as direct3d?

Also, as far as the "line down the middle of the screen" thing, it's not actually a visible "line" -- it's just a straight path down the middle of the screen where it looks like the pixels rearrange a little bit. Hard to explain, but you can clearly see it if you look at the "n" in "sounds", the first "p" in "imperceptible", the "t" in "taxed", and the "a" in "and" (right below "taxed). Once you find the "line", you can look up and down at different textures and see the change I'm talking about if you're switching between the two images.

Edit: I did some experimenting with my HD 4000 graphics options and turned off everything that looks like it might have any effect whatsoever like that. Most everything was already set to "application settings", though, so there wasn't really much to play with. But, after turning off or changing anything that I could, there was no difference. I took new sets of screenshots and the blurriness with overlay persists.

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