Debug screen



The debug screen is a screen that is triggered when the F3 key is pressed. It shows the chunk cache, the memory usage, map seed, various parameters, the player's map coordinates and a graph that measures the game's current frame rate. It can be very useful for telling other players your map location, checking for mobs and various other purposes. As of a recent update, the debug screen no longer shows the player where spawned, nearby mobs are located.

The world is rendered in multiple passes. The first pass draws normal, opaque blocks. The second pass draws water and ice. This makes sure water is always drawn on top of solid blocks without relying on depth sorting.

Legend:

Rendering Graph
The graph at the bottom screen displays rendering performance information. The height of each bar indicates the time taken to render each frame.

Green bars represent a frame rate higher than or equal to 60 frames per second, and red for less than 60. Once the graph has moved all the way to the right of the graph area, it will return to the left and begin to overwrite older bars.

The speed at which the graph writes new bars is dependent on the current frame rate, as one bar is written per frame.

As of 1.9pre3 there are seven pie charts in the lower right of the debug screen that display real time rendering information. The charts can be cycled using the 0 and 9 keys.

History
In Indev, Infdev, and early Alpha versions, the debug screen only had what we recognize as "the top part with all the numbers". This debug screen was not activated with F3, but as a toggle in the options. In Alpha 1.1.0, the debug screen was no longer listed as an option and required F3 to be held down to activate. In Alpha 1.2.3, the FPS graph was added.

In Beta 1.3, the debug screen, along with other F# controls, became a toggle. Also, between Beta 1.3 and Beta 1.8, when you activated the debug screen, it would show numbers above every mob; these numbers being the mob's Entity ID. These would be visible through blocks, hence making F3 a very useful mob-finder,(though, it did generate a small but noticeable amount of lag through extended use for some players) which also was considered cheating and took away from the game. Because of this, the Entity ID label was removed in Beta 1.8.

Bugs

 * If you exit to the main menu with the debug screen open, it will stay on the screen. Pressing F3 in the menu has no effect, so loading another level is required to be able to hide the debug screen.
 * Opening a chest or opening the Achievements screen with the debug screen on turns the debugging area grey. The text does not turn grey, however. This will not crash the game.
 * If you quit while it says "respawn", press f3 and then log in again, it will show you the coordinates of your death.
 * At very low frame rates the graph can rise high enough so that it will cover values like the coordinates. A mod to fix this can be found here.(The mod is a bit old, may not work with current version, 1.8.1 is current as of October 17th)