Programming Pseudo 3D Planes aka MODE7 (C++) 

Hey thanks Leo. I must apologise, I thought you'd stopped posting videos as I wasn't getting any notifications, and somehow the bell had been switched off - I'm catching up now and will likely steal some of your ideas :D.

ow i would be honored, but my stuff are already things that i get from someone else, so no problem xD ...

Javid don't you know, Stealing is just a programmers form of collaboration!

@@javidx9 Me too creating a Video Game with Mode7 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9YDV2DEM3gc.html

Thanks Xavery :D

Hi Kartik, thanks, no problem!

Thats really nice of you to say AcceleratingUniverse, I appreciate it a lot, thanks!

That horizontal black bar in the center should only appear when you have an odd number of pixels for the screen height, right? Because if the height is even, then that infinity value falls right between the two pixels in the center.

Hi FuzzyCat, yup, spot on. Not many monitors with odd rows of pixels though :D This is often a problem with computer graphics, as things tend to favour powers of two, but there is no accessible middle pixel in those circumstances.

Thanks Jelle!

Thanks Sage, another GBA candidate? :D

haha yes i was thinking about it! :) Maybe adding this to the raycaster. Or make a gba racing game would be fun. I wonder how hard it would be to remove floats and division.

Thanks Darko!

Thanks dasten, no problem!

Hi Matt, that'll be the subtle mind control working via the last few videos...

All good ideas, though the console is limiting when it comes to scaling and colour resolution, but if you are not in the console, good stuff!

I didnt know darbs had started running F-Zero now, hmmm, I'll check it out, but I didn't thing there was much room for strats in that game - obviously I'm wrong if darbian is doing it lol

Well, F-Zero is a hard game. You don't need glitches to make it interesting for a speed-runner. Darbian was doing F-Zero in a 12 hour challange which was just speed running a new game 12 hours one weekend. greetings

Thanks TIG!

Psychic Coding :-S

No problem buddy. This technique would be more complicated to do on a game boy so thats quite impressive.

Cheers Mark.

Kind of, its all an optical illusion really. If you add more scenery like trees for example, you can make the illusion even more compelling.

Cheers Neil, yeah I think theres lots of potential. I've just been fiddling about trying to add height to it too. I reckon there're some interesting videos to be made with this. I have some plans for a racing game too.

Btw series is both singular and plural, so it's 1 series, 2 series, 3 series, etc.

There's always that one guy that doesnt like retro pseudo 3d graphics emulated in a windows command prompt...

Always one 🙄

It happens Jim, it happens, I've a folder full of "work in progress"

Yeah, I dont like how the sky moves up and down either, I think for a flight sim you would need different sample coordinates for the sky and ground

I guess that it would look nicer to just have the sky as a simple background that simply pans around matching the rotation of the camera so it looks like unfinite distance. Maybe have a cloud layer or two as separate mode 7 textures though to keep things more interesting. But have them fade out towards the horizon to make it nicer.

Sky should be considered very far away and thus it can be rendered completely stationary, you just rotate it with the player but dont move it.

Yes I think we will, its a great starting point for racing games, flight sims, shooting games...

Thanks! The Pixelgameengine uses a single opengl1.1 call to display the screen buffer on the screen.

Just an idea but i haven't seen a good tutorial on this before and i look a lot.

Hi Brek! I think you could easily replicate the projection with a projection matrix and draw things into your scene. In fact use the matrix to also create the sampling points for the FOB quad.

Hey Mac, Happy new year to you too! Yes I do everything using the CPU. Introducing the GPU would make some of the videos quite boring given all the setup code required.

@@javidx9 Says the 1 year younger Javid. Now you have decals in the PGE 2.0 :)

Yes, all the code I present on the channel is a solo project (unless I explicitly state otherwise). The trick is to just keep things as a hobby, if it stops being fun then dont carry on with it.

Hi and thanks Aikou! I have a couple of videos about programming in general for beginners, but ultimately no, I dont have any aimed towards complete beginners. I try to make videos which dont even rely on you using C++, even though I do, the concepts are easily portable to other languages.

@@javidx9 Oh that's fine, I'm acquainted with some basic concepts of both Java and C++ but I asked the complete beginner part because that's pretty much how I see myself when I watch some of your content lol (yes, the 3D engine videos blew my mind). I'm teaching myself how to code so I don't really know much other than the two languages I mentioned but I'll try to pay more attention to your "code-it-yourself" series. Thank you so much for replying to my comment.

Thanks Goupil! The Snes had hardware specifically capable of performing an Affine Transform, which is the effect emulated in this video. To be fair, I too could have implemented an affine transform directly but kept it simple with linear(ish) interpolations. On our modern hardware at these resolutions its no big deal, but back in the 90s, doing a per pixel affine transform would have been quite a challenge without dedicated processing units. The megadrive lacked such additional hardware, but had its own features that could produce effects the snes couldnt.

Wow that was quick, thank you. I've been thinking for a while about 3d prototypes with Mode7 rendering on Unity, for nostalgic esthetic purpose. Since there is no such concept as canvas on Unity but only textured quads, so far the only solution I could consider would be to add a purely graphic "pixel-perfect layer" above the regular 3d display, which would be seen through a camera with no perspective. In this extra layer, some 2d looking-squads would be displaced "pixel by pixel" (an arbitrary unit) following the edges of the models in the back-layer (sorry it's a bit hard to explain for a non-native english speaker). I didn't find much work on this subject, so if some other persons had been working on it, I'd be very interested to hear some alternative solutions. Keep up the good work!

it is possible on Mega Drive through pure code :) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-X975THoQ6DE.html

kappa

Hi roberto, in principle you are correct, perspective is not linear. When my calculations were linear, they generated curved looking projections. Dividing by fSampleDepth straightens it out because I need a 1/Z somewhere in the transformation.

@@javidx9 OK I see. Cause actually you can find the same equation when doing ray casting on a plane. If you got a vector v= (x, y, z) and a plane which equation is z=-1 assuming that the player is a point p=(xp, yp, 0) the intersection with the ray casted from the player will be finded by resolving the system of p+v*k and z=-1. So by resolving pz+vz*k=-1 which gives k=-1/vz - pz which gives k=-1/vz cause pz=0. So p+v*(1/vz) gives the intersection point. So we can get x and y coordinate from the plane with it. And it is exactly the formula you used. But actually mine is multiplied by - 1. It should invert x and y. Do your rotation is inverted? By the way the formula I gave you is based on raycasting. A way to produce a kind of perspective vision based on optics geometry and physics. And it seems to work.

Hi Pablo, you can render a sprite the same way I have done in many videos, making it rotate is tough. If looking top down, you can use a rotational transformation matrix to rotate the sprite, looking from behind as would be the case here, you would just need several sprites.

It "should" compile with 2010, however a lot of my more recent videos will probably not. The tetris code i present here is simple enough that any unsupported features could be worked around quite simply.

thanks, one question though the capture listing is it serving as lambda am still learning that syntax and how it works, i hear it works only on 2011 and upward releases

i share your persona, am really a lone wolf and i don't do too well in groups ,i read alot and am way too selective.

Yes, lambda functions need a recent version of C++, you can just replace them with a regular function though, it may just need a few more arguments.

I dont think the pixel scaling would be the culprit, could be the organisation of the textures is different? dunno...

Hi Ian, yes there is. If you angle the camera downwards, you are reducing the near and far plane distances, so that's easy enough. The problem is this wont look right because we expect the horizon to raise as we look down, so you will need to do this also. In this video I split the ground/sky 50/50, you may need to try other ratios until it feels correct.

@@javidx9 That worked great thanks!

For a better formula see my blog at: tegtips.blogspot.com/2019/04/correcting-pseudo-3d-planes-aka-mode7.html

Hi Kavukamari, sometimes, you just need a little hack! Chances are you're right, you are getting some overflow/underflow mess for that particular row. Without knowing your precise implementation I can only speculate, but if a hack works, then go for it!

Sprite files store ASCII characters that make up the "pixels" used in the console game engine, dont forget that ultimately this is still just a windows command prompt, so the concept of "pixel" does not really apply. A PNG file is a traditional format image file which stores pixels in RGB format (with some compression). My Code-It-Yourself Frogger video introduced sprites and how they work.

Thanks so much for the explanation! I'll check out that video

Yup, I could get at least 25 videos out of this! Space shooter, underwater shooter, WW2 simulator...

javidx9 Programming gives us almost unlimited possibilities, and that’s what I love about it - there’s virtually unlimited things people can do with code :) I view programming as a sort of art form in that regard 😛

Stop talking

It could certainly be used for planes in a ray caster yes!

The "effect" of mode 7 is achieved purely as a transform distorting a 2D image. Arguably, 3D doesn't actually exist since it must be in 2D form to display on a screen, but that's a whole other video. The background can be whatever you want it to be, 8 see no reason for restrictions, and rotation is often more complex than just scrolling horizontally.

@@javidx9 so theres even no 3D space at all??? And how about the backgrounds, for what i do know is that the snes cannot do 4 backgrounds and mode 7 atonce no, so how were those multi scrolling backgrounds done in street racer and mario kart???

start the loop with y = 1

Hi SM, I don't know Python very well so I can't help you, sorry about that

The math is exactly the same, what you'd do is either modify texture and then render it using pygame or instead use shaders to sample textures on a quad that would take up entire screen (since this problem is actually horribly parallel).

I'm workin' on it! I'm workin' on it! :D

Its fake mode7

Hi Draconita, this is a single file custom game engine which I use for all my videos called olcConsoleGameEngine. Its simple to use and has the odd characteristic that everything you see is rendered inside a windows command prompt. The source is all available in the description. Ive recently released a newer version which is more conventional in terms of graphical style but retains the simplicity, thats called olcPixelGameEngine, and I have a video exclusively about this too.

Hi GoldenGuy, ill be following this video up with something similar to what you're asking in due course, calculating the position is no different from translating a pixel in the map into screen space, as the map pixels are in world space too. The tricky part is scaling the sprite in accordance with the perspective. This can be derived from the scaling mechanism in use too, but may need some experimentation.

@@javidx9 Mr Javidx I am also struggling to calculate the screen position, could you please give a couple pointers? I understand the frustum corners but am unable to place the object on the screen correctly.

Thanks! lol, how do I say Mario Kart? :D

M-aaa-rio kart... idk it might be just how different people pronounce it, but it seems that in America everyone says it differently

Just curious, how do they say it in America?

Mar as in mars the planet e-o so mar-e-o

That looks like multiply.

Yes you can! Theres a port for pixel game engine available in the contributers folder on the repo. I try to make my videos platform/language agnostic so the algorithms are still going to work.

Now that's a heavy question and no matter what answer I give, it will be wrong :D My experience in IDEs, there is sadly little that is comparable to Visual Studio in terms of its integrated debugging facilities. There are many code editors (I believe VS Code is very popular) but few that really permit debugging as fluidly as Visual studio. However, as I'm not a frequent linux user, I could be very wrong in this regard.

you can do it the hard way with any text editor of your choice and a terminal, plenty of programmers do this. i personally recommend Visual Studio Code, it Open Source. and provides the best of IDE like features, while being very customize able. a RU-vid Search for VS Code C++ should give you all kinds of information tip and tricks for getting started. it does require some setup, but that is because it can be tailored to YOUR workflow and how you like to do things. codeblocks is another very popular IDE, Along with QT Creator. most of these can usually be obtained from your Linux distro's Package Manager. sorry if im late and non of this information is needed. Good luck in your Linux Programing Journey :D.

Yeah thats a great idea Ola!

You could be right, this was in debug mode so its actually about 120fps. However its the variation of the maps that causes the performance drop. The algorithm is a fixed level of complexity so the performance is not related to the properties of the frustum, instead as the pixels become more distinct in appearance the windows algorithm that renders the characters takes a nose dive.

> instead as the pixels become more distinct in appearance the windows algorithm that renders the characters takes a nose dive. Those are probably cache misses; if you don't hit the same pixel twice, each pixel has to be loaded from RAM. (Since today's RAM is usually cached in small blocks, about 32 bytes IIRC, that doesn't hit hard unless the pixels are REALLY far apart or from different rows of the texture.) If you profile the program and see a drop in your subroutine rather the API call, that's what causes the drop, even though the number of operations per frame doesn't change. I found another performance issue: Instead of computing fStartX + (fEndX-fStartX)*fSampleWidth, you should consider precomputing fStepX = (fEndX-fStartX)/fScreenWidth and then use a for(x) loop that only adds: fTempX = fStartX; // ditto for fTempY for (x blahblahblah) { fTempX += fStepX; // ditto for fTempY short col = sprGround->SampleColour(fTempX, fTempY); // ditto for sym Draw(blahblahblah); } That won't alleviate the caching issues, but mipmaps will ;) Oh yeah, they look better, too.

Hi Artemis, I did a little bit of NES programming once. The problem with console programming (lol as in gaming console) is the code you write is highly specific for that platform, so you need to invest a lot of time learning how the platform works. There are a few game boy programmers on my discord server, they've managed to find C++ dev kits for the platform too.