The Convergent Billboard

The Convergent Billboard is now live on the mainnet.

What it is

The Convergent Billboard is a bonding curve linked to an advertisement.

A bonding curve allows the user to buy and sell the Convergent Billboard Token (CBT) from the smart contract directly with continuous liquidity. Buys cause new tokens to be minted and added to the total supply which increases the price for later tokens. Sells cause the sold tokens to be burned from the total supply and decrease the price. These minting and burning operations follow a determined price path. In the front-end you can see a stark blue line that travels from the origin (0,0) of the chart to the top right corner (1000, 1): this is the price path for the CBT.

An advertisement is a poster or banner that is meant to attract public attention. Under the price path — let’s call it the “curve” from now on — an image will be rendered. The rendering surface for the image is the area under the curve for the amount of tokens which have been minted into the total supply. So as people buy and sell tokens from the curve — what we call the speculation market — the display surface of the billboard advertisement will grow and shrink.

The cost of changing the advertisement image is 1 CBT. There is no set time duration that your uploaded image will remain on the billboard. At any moment you or someone else can pay 1 CBT and change what is displayed.

There is a maximum supply of 1,000 CBT. When this limit is reached, the curve will not allow any more buy operations. However, it will still allow sells. CBTs which have not been used to change the billboard can be sold back to the curve and users can purchase CBTs again up to the limit. When the thousandth CBT is used to change the billboard, that image will be final and no one else will be able to change the billboard again.

Whenever 1 CBT is used to change the image rendered on the billboard, the value for that token is taken from the left hand side of the curve — let’s call this the cliff. See the diagram below for a visual explanation.

In this chart you can see the area A marked in red which represents the amount of ether that is sent to us when someone uses 1 CBT to purchase an advertisement. The left side where the red area touches the black area is the “old cliff” and the right side where it touches the blue area is the “new cliff.” In this example, the blue area would represent the amount of ether held in reserve by the contract for the speculation market.

How to use it

Convergent Billboard Tutorial

FAQs

How does the chart know what the latest image is? Where does the image get uploaded to?

The image is uploaded to the Interplanetary Filesystem (IPFS), a decentralized and content-addressed file storage solution. After the image is uploaded to IPFS the DApp will submit the hash (what’s known as the content address) to the Ethereum blockchain. The hash will get emitted as an event log and the DApp knows which event to watch for the latest location of the image to be displayed. Everything is built on the decentralized tech stack of Ethereum and IPFS. The only thing that is on our server is the hosted front-end, but even that can be ran locally by pulling the source from our GitHub!

My buy transaction was reverted! What happened?

Check Etherscan to see if there were any other buy transactions within a few blocks — it’s possible someone else was buying CBT at the same time. If this is the case what likely happened was that in between the time it took for you to make your transaction and for it to get mined, the other transaction went through and drove the price for the token higher. So your transaction was out of date and didn’t send enough value to cost the new price of the CBTs! We are researching ways to do partial buys or “limit orders” to mitigate this situation.

Why we built it

At Convergent we are building a personal economy platform, a bonding curves smart contract framework and generally experiment with the subset of cryptoeconomics known as curation markets.

Billboard is meant as many things at once — it is a live proof of concept demo of a bonding curve, an experiment in a novel way to sell digital advertisement and perhaps most important: a way to fund our team.

If we are right that this is an exciting and novel tool we are building — we hope that the billboard will be able to sustain our initial development. We build all of our software and tooling open source under the AGPL-3.0 license. Yes — this goes even for The Convergent Billboard itself. If people think what we’re doing is cool we hope they will purchase advertisement. We believe in the power of the crowd.

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