How To Use Filters In Dosbox

Last Updated on June 29, 2020.

The basic version of DOSBox does not contain back up for 'shaders'. Those little bits of code and configuration that can make a modern retro gaming screen look cell shaded, dotted like an sometime school CRT monitor, or even curved and blurred similar an old Television set tube. So how exercise I get shaders? We have to utilize a fork or variant of DOSBox. Let's run a comparison of these shaders in a MSDOS Retro Gaming screenshot session of DOOM.

I have plans for three dioramas. One is consummate – the C64 years. I notwithstanding accept an Atari 2600 and IBM PC diorama to practice, and the latter is a fleck more than technically challenging when it comes to actually playing the games. Not only do I take to worry most DOS games, simply Windows 3.one, Windows 95, and even some Windows 98 gaming, and attempting to make all of those games piece of work on 1 pocket-sized PC that will host the actual gameplay.

Why DosBox at all?

Between the onetime copies of games I have on CD and floppy images (I saved a lot of crap digitally if not physically), the actual CDs themselves, and sites like GOG.com, I'll be able to relive a lot of my one-time gaming days. This is, of grade, thanks in no small part to a petty programme called DOSBox.

From their site to explain it best: DOSBox is an emulator that recreates a MS-DOS compatible surroundings (complete with Sound, Input, Graphics and even basic networking). This environment is complete enough to run many classic MS-DOS games completely unmodified.

It's the de facto standard for running DOS games on modern hardware.

This article refers to functionality I utilized in a specific DOSBox variant known as DOSBox Optionals, compiled by Marty Shepard. More info on that beneath.

I am 32 flavors and so some

To that terminate, in that location's nearly always a variant of DOSBox that gains popularity for a while because DOSBox 'proper' doesn't back up every single feature a DOS gamer might desire to apply when playing a game (east.chiliad. Voodoo 3Dfx support). At that place are a decent number of variants that fall under the label of 'SVN Builds', you tin check em all out here: https://www.dosbox.com/wiki/SVN_Builds.

Ane of the nigh pop variants today is called DOSBox ECE, standing for Enhanced Customs Edition. It emulates 3Dfx hardware and supports upward to 384 MB of ram, two things that the standard DOSBox build doesn't cover.

Remember that you don't accept to utilise ane version of DOSBox for every single game yous play, although if you could, that would be ideal from a configuration management standpoint, as each variant may have different config file options available.

Now we have variants like DOSBox X, SVN Daum, ECE, and fifty-fifty CRT, which commencement caught my eye because, while I don't always play with shaders (I dislike them on VICE), I wanted to see what the DOSBox earth had to offer me. All the same, I wanted a relatively recent version of DOSBox with shaders. The hunt begins.

DOSBox CRT is shut only no cigar

DOSBox CRT fit the bill at first – it'southward substantially DOSBox 0.74 with a custom shader to give that existent CRT expect and feel. Every bit much as I liked the inner screen rendering of it, this version essentially paints a CRT border around the screen that becomes part of your DOSBox window… I did not find this palatable:

Go away monitor border… I didn't ask for you.

Skilful job and a nod to Mattias Gustavsson for compiling his custom shader piece of work into DOSBox. Information technology just wasn't for me. So our hunt continues. I didn't want to use Retroarch for this, and I wanted something a petty more recently maintained…

An Optionals requirement is institute

I stumbled across another DOSBox variant called DOSBox Optionals, created by Marty Shepard with about latest enhancements of DOSBox ECE, standard DOSBox, and other patches people take released that aren't incorporated into the 'standard DOSBox' build. Marty has done a fantastic chore of grouping all of these enhancements into a unmarried DOSBox build that besides supported the shader patch by duganchen. VOGONS thread almost that back up here.

I downloaded and extracted DOSBox Optionals and opened up the dosbox.conf. Yikes! The sheer number of options and documentation to each option compared to the normal DOSBox install was amazing. I recommend trying it out – I've tried a handful of titles with information technology thus far and they've worked, though I did notice a speech pitch issue. I'll encompass that afterward in this postal service.

Throwing Shade…rs.

And so without any 'shaders'… What does DOSBox Optionals look like? Let's compare shader to not shader. Given that I'm scaling my screen upwards, my no-shader view will accept a slight blurring to information technology – but that'south not the shader.

Using DOSBox Optionals I took a 'before and later on' screen shot of 'no shader' and the 'crt-lottes_mod' shader. You can drag the vertical slider below with your mouse and immediately see a difference.

Delight note that the new defaults (scaler=none, attribute=on) are needed for the shaders to work as designed.

The results? Immediate shift to a more than 'dot-based' look, a little darker and very much closer to a curved CRT. Compare yourself – the left side is without any shader and the right side is with 'crt-lottes_mod' selected. Drag the line to motion your comparison from left to right.

Let's zoom in and see what information technology looks like:

I'thousand impressed. Y'all really get a sense of the dots and CRT nature of the view, and the phrase 'dot pitch', which I haven't thought about in probably a decade, comes right back like it was yesterday. This isn't just whatever simple browse-line filter.

Quick rundown of 13 shaders in DOSBox and DOOM

What about some of the other shaders? Permit'south take a await – you tin use the compare slider to wait at the same screen shot of DOS and the same screen shot expanse of DOOM and compare shaders. I imagine one shader might exist good for ane game and one for another – or if you're playing CGA, EGA, VGA, or ANSI text games, you lot very well might want a specific kind of shader for those resolutions and colors.

For me, I've actually got my eye on crt-lottes_mod and crt-easymode. GTU looks similar a contender equally well. Some of these other shaders are just nuts – FixingPixelArt gives i hell of a mistiness for example, and the xbr (#four,#v) shaders requite it a 'behind stained-glass' feel to me.

Modifying shaders for testing

As much as I like crt-lottes_mod, I have some tweaks I'd like to make:

I don't like curvature shaders. I know information technology's trying to be more realistic, it'due south just and then damn off-putting to me, I'd like to disable it.
It'due south a little too dark – I'd similar to increase the brightness a picayune bit.

I started to wonder – if I do this, does it finish upwards looking like crt-easymode? Let's tweak information technology a flake and find out.

I'one thousand going to caput over to the SHADERS/crt-lottes_mod.frag file and tweak a few values:

#define warpX 0.000 //0.021, 0.007 #define warpY 0.000 //0.045, 0.021  #ascertain brightboost 1.0

Let'south compare crt-easymode to my custom-mod-v1:

Granted, you lot could spend all solar day playing effectually with parameters, and while I feel the lottes_mod definitely has a lot more in the mode of customization options, I'm leaning towards crt-easymode fifty-fifty with the modifications I made to flatten lottes and brighten the screen. This is just to get something going to see if I similar it enough. It's also a footling lighter on the GPU than lottes will be from what I gather, which is good since I won't be playing my DOSBox titles on a super high end modern machine.

DOSBox Optionals comes with gratuitous Chipmunks

Once I found a shader setting I wanted to try out for a fleck, I needed to exam a few titles on DOSBox Optionals to make sure it worked for my gaming tastes. Optionals comes packaged with a demo for DUNE2, ane of the first Real Time Strategy games, and a Westwood classic.

I fired up the demo and as shortly equally the voice synthesis came on, I could tell something was only a scrap… chipmunky. This was with default settings that come with the DOSBox Optionals install. Listen to this:

This did *not* happen running the same DUNE ii demo on regular DOSBox, then I knew it was something specific to Optionals. But what? What patch is inserting Alvin into my games? I found this VOGONS thread referencing elevated pitch in DOSBox, calling out this code in particular:

I found a reference to Goldplay while searching the DOSBox Optionals repository:

Snippet pulled from https://github.com/MartyShepard/DOSBox-Optionals/hulk/master/dosbox/tOptionals/src/hardware/sblaster.cpp at the time of this writing.

So, Goldplay. We're now just a fleck above my pay grade – it's DMA transfers, sample rates, and IRQ programming. Even so, I ready goldplay = true in the dosbox.conf and voila:

Proficient bye, Alvin. The sands of Arrakis take finally rid us of your presence.

I'll have to keep that configuration option in heed in the future if something seems off in Speech communication. But between DUNE2, the demo and the game, forth with Ultima Underworld, I needed to have this setting set to true for speech to audio proper.

Conclusion

Got some shader settings you like? I'd love to know if there'south a favorite preset or game/app you use a detail shader for. I'll probably stick with crt-easymode for at present, though I might await at the shader configuration and tweak a few things and see what happens. That's what shader configs are all well-nigh – experimentation – considering if a shader just isn't doing anything for y'all, and it'south not reminding you of the monitor model you played that game on – tweak information technology!

References

https://github.com/MartyShepard/DOSBox-Optionals – DOSBox Optionals Repo
https://github.com/duganchen/dosbox_shaders – Duganchen's shaders included in DOSBox Optionals
https://mattiasgustavsson.itch.io/dosbox-crt – DOSBox CRT Build
https://world wide web.vogons.org/viewtopic.php?t=33896 – VOGONs thread regarding sample rate and DMA for SoundBlaster devices
http://filthypants.blogspot.com/2015/04/more than-crt-shaders.html – A good article referencing example shots of these shaders utlized in other emulators like RetroArch.
https://emulation.gametechwiki.com/index.php/CRT_Shaders – General Shaders article – references a lot of shaders converted over to DOSBox (Duganchen'south build) and included in DOSBox Optionals.
https://scalibq.wordpress.com/2017/03/12/dma-activation/ lots of technical information but references SoundBlaster GoldPlay

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