Tuesday, November 29, 2011

Why we should stop saying "vertical slices"

The other day I came across the this blog post by Ron Gilbert called The Vertical Slice in which he rails  against the creation of vertical slices.  The following quote struck me:

"Vertical slices might work in a medium where you start at the beginning and grind though in a fairly linear fashion and what comes out is 90% complete.  Maybe writing a novel works this way, but making movies and games do not.  They are an iterative processes.  You build foundations and the build up from there."

I love his image of the Mona Lisa's vertical slice.   But Ron is using a different definition of vertical slice than I've always used.  To me a vertical slice means is that we develop a feature to the point of knowing its value and use that knowledge to adjust the plan.  The point being that the plan won't tell you how fun something is: the game will.

Ron's definition is that vertical slices emerge from a plan that defines all the slices up front.  This might be a better approach from an engineering point of view over waterfall (fixing bugs along the way, etc), but  it abandons the benefit of iterating on a plan with a working game.  It doesn't surprise me that he's against that.

So maybe we should stop using this confusing phrase.  Maybe we should call it a "game increment", or something.  I'm open to suggestions.

By-the-way, here is how portraits were iterated on:

Do a Google image search on "unfinished portraits" and you'll see a lot of these, all with the heads nearly completed and little else in the portrait done.  Can you guess why?   It has something to do with prioritizing risk, and stakeholder value....things often spoken about in agile circles centuries after this was painted.

Also, da Vinci iterated on the Mona Lisa as well.


Anonymous said...

Its just a far to literal interpretation of what a vertical slice is.
It's an analogy to help with understanding, but it has limitations, just like all analogies.

Clinton Keith said...

His or mine?

Agreed that analogies have limitations, but it doesn't seem to "help with understanding" in this case.

Joseph Humfrey said...

Yeah, we need to stop using the term "vertical slice" because it's misleading. But I completely agree, the idea is perfectly sound.

One of the problems is that different games have different requirements in a vertical slice. So, to prove the concept of a racing game, the limited set of elements you need to make a demo is completely different than that of a point-n-click adventure.

Also, in my experience, different team leads with different backgrounds can underestimate the work that isn't their original discipline. For example, a lead with an art background might work to design a vertical slice which minimises the amount of art assets required, without realising that the design requires all the code features of the final game!

Essentially, I think "vertical slice" is misleading because people think they understand what it should mean simply because they can visualise the metaphor!

Clinton Keith said...


Excellent points. Typically agile teams will use product backlog items with a "definition of done" that is established by the product owner. That way a multi-iteration feature can be developed in the appropriate way.


David Barnes said...

I love your point about portraits. That's brilliant.

Can't comment on the game dev stuff.

Clinton Keith said...

Tobias Meyer introduced the portraits to me. It does make a point!

Web Design Los Angeles said...

I am learning about them here...good food for thought.There are a lot of techniques being used to design effectively.Intelligent graphics I must say.

Mobile Game Developer said...

I agree with David Barnes.

Anonymous said...

I also think you are taking a simple metaphor to literally. To me, the unfinished portrait represents vertical slices. In portraits the most critical element is the face. So that’s what they did first. In addition, at this point they have options. They can stop now, cut out the face and sell that. With a little bit of work they can have a bust, or with even more work they can finish the painting. That’s what the vertical slice metaphor enabled. In contrast, a horizontal slice could be to paint all the blue sections, and then paint all the red sections, and then paint all the yellow sections, and so on. And after painting the red, blue and yellow sections I still may have nothing of value to the customer.
In the end, you have to figure out what is the vertical slice that reduce risks and deliver value incrementally is for your project.

Clinton Keith said...

What metaphor is that? I objected to the definition that:

"Vertical slices might work in a medium where you start at the beginning and grind though in a fairly linear fashion and what comes out is 90% complete".

The Mona Lisa metaphor was not mine.

What I've always accepted as a vertical slice IS encompassed by the unfinished portrait EXAMPLE (not a metaphor, since it is literal). We actually agree on that.

What was actually said in the article about why we might want to stop using the phrase "vertical slices" is that there is a lack of agreement on it. A phrase like "product increment", for example, is more generally accepted and agreed upon.