NES graphics – Part 1

[jonny_eh]

I love articles like this. It reminds me about a similar one about the Super Game Boy: http://loveconquersallgam.es/post/2350461718/fuck-the-super-...

[6502nerdface]

Great, approachable introduction to how NES graphics work under the hood; looking forward to Part 2.

In the meantime, interested nerds can feast on the wealth of information available at [1], which, though a bit disorganized, goes deep into the implementation of the NES's Picture Processing Unit and its programming interface.

[1] http://wiki.nesdev.com/w/index.php/PPU

[aout]

During that time, Nintendo knew how to work with game studios. The color palette is one of the most powerful examples I remember, it encompasses the technical and the artistic domains, developers and designers. With the SNES they got even further by adding composition in a way that was incredibly intuitive. Glad you produced this article. So much memories.

[chii]

> it encompasses the technical and the artistic domains

these days, the amount of knowledge required in those two domains are such that no one person can be an expert in both ( at least,for a non-genius!). Think about 3D artists, and think about people who write the pipeline and tools etc for them - one does not know anything about the other really. I wish there's a way to simplify it all so that modern games can be made just as "simple" and intuitive as the old 2D bitmapped graphics.

[coldpie]

Funny thing about the NES palette is it's actually spectacularly poorly chosen. It has no yellow and dedicates 10 entries to black.

Source: http://www.thealmightyguru.com/Games/Hacking/Wiki/index.php?...

[bluedino]

The color limitations of the NES made it look so dated so quickly. The resolution isn't much lower than the SNES but there are so few colors available compared to the 32,768 colors of the SNES.

[tbrock]

To me it seems as if the PPU is the most poorly explained (or difficult to understand) component of the NES. Most documentation heavily glosses over details and specifics or doesn't provide any reasoning as to why such a system was designed. This is a great guide.

If you have some spare time and want to tinker a bit, writing your own NES emulator is a great way to learn something new (or learn a new language if you've done it before)

[loganfsmyth]

Definitely second writing your own as a way to learn. I wrote one that could mostly play pong a while back and it was super satisfying. The PPU was definitely the toughest part.

[otabdeveloper1]

> Original NES developers probably had some sort of toolchains, but whatever they were, they have been lost to history.

"Lost to history"? Really? The developers are still alive, you could have, you know, sent them an email and asked.

[bluedino]

This webpage:

https://seanmalstrom.wordpress.com/2011/08/19/email-a-look-i...

shows Nintendo programmers plugging away at HP 64000 which was likely corporate-owned and long destroyed

http://en.wikipedia.org/wiki/HP_64000

[krivx]

Japanese developers from that era are famously secretive. I have heard that Nintendo has a reputation for being particularly shortcoming with information to journalists or historians.

[unexistance]

eeeh NDA will probably prohibits, hence lost

[rcr]

What advantage is there to storing the high and low bits of the 2 bit depth CHR separately, as mentioned in footnote 2?

[muhbitplanes]

This is the ol' chunky (all of the bits for a pixel stored adjacently in memory) vs. planar (image broken up into separate "bitplanes") graphics debate. Planar was very common for early 2D hardware, as it was the natural extension of 1-bit monochrome display hardware, which would load a byte at a time into a shift register, shifting a bit out per pixel clock. Instead of needing to redesign the hardware around a larger shift register, you could just duplicate your existing shift register, shift them out in parallel, and combine the results with some simple logic.

It had a variety of benefits for simple 2D composition. For instance, it allowed for flexible bit depths in video modes. The Amiga (IIRC) allowed you to set up video modes with anywhere from 1 to 5 bits per pixel, while the SNES allowed 2, 4, and 8 bits per pixel formats; lower depth modes would simply load the unused shift registers with 0s, and everything would work the same. With chunky pixel hardware, this would have been unfeasible at the time, as the pixel format packing would change too much between bit depths. It was a handy feature to have, so that, say, text in an RPG could be placed on a monochrome layer that would not take up as much video memory, while the rest of the game could be rendered in full color.

The NES doesn't support flexible bit depths, but a similar principle allows a simple kind of "compression" when storing compressed graphics data in ROM: for a monochrome font, you wouldn't need to store the upper bitplane, and you'd just zero it out when loading the font. For chunky hardware, this process would be a bit more involved than that (no pun intended).

Of course, once you advance beyond simple 2D composition to software rasterization, the planar format becomes a liability. Rotating and scaling a bitmap, for instance, would involve making multiple unpredictable read-modify-write memory accesses per pixel, instead of just directly overwriting a pixel at a time.

Here are some links that discuss some of the other tradeoffs of the two formats, like how you can use planar formats to implement simple alpha blending effects for shadows and the like:

http://oldwww.nvg.ntnu.no/amiga/amigafaq/AmigaFAQ_16.html

http://www.sega-16.com/forum/showthread.php?9265-For-the-Tec...

[userbinator]

One way to think of it is basically as a text mode with customisable graphics for each character. It's also possible to "race the beam" and change them between lines, giving rise to far more interesting effects.

[faragon]

Very well explained. I hope next parts will address screen scrolling, sprite animation, and "raster effects".

[unexistance]

very good read... pretty sure these knowledge have their place in our modern scenario, say like sensors?

[Zardoz84]

Interesting. Looks like that it evolved from a text only video system, but using 2 bit shade per character and selectable palette per character. Indeed, very clever.

[blt]

cool post! the development process must have felt so different then. constraints bring out creativity. today's hardware is amazing, but there's something special about knowing every corner of a system, working right on the metal. it might even be within reason to imagine building a system like this out of 74 series logic in the garage...

[distantsounds]

This is an amazing read. Thanks.

[grimmdude]

Very interesting