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updated "Assembling a chunk" section for anvil format

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Andrew Brown
2012-02-19 21:55:47 -05:00
parent 1d2f908cb6
commit dc50f6a044
1 changed files with 12 additions and 27 deletions
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docs/design/designdoc.rst
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@@ -344,39 +344,24 @@ So the total size of a chunk section in pixels is 384 wide by 384 tall.
Assembling a Chunk
------------------
Now that we know how to place blocks, assembling the chunk is a relatively
simple process. Frist, create an image 384 by 1728 pixels. Then, paste the
blocks in order from back to front, bottom to top. This ensures that block
visually closer to the viewer are drawn on top, while blocks that should be
obstructed are drawn first and get hidden.
From the data file on disk, block information in a chunk is a three-dimensional
array of bytes, each representing a `block id
<http://www.minecraftwiki.net/wiki/Data_values#Block_IDs_.28Minecraft_Beta.29>`_.
The process of assembling a chunk is essentially reading these values, looking
up the appropriate pre-rendered image representing that block type, and pasting
it on the chunk image at the appropriate location.
First, a bit about how blocks are addressed in a chunk. Consider this diagram of
the *bottom* layer of a chunk: Y=0.
Now that we know how to place blocks, here's how they are arranged to form an
entire chunk section. The coordinate system is arranged as shown, with the
origin being at the left corner.
.. image:: cubepositionimgs/chunk_coords.png
:alt: Illustrating how cubes are addressed in a chunk
The 16x128x16 array of block is iterated over. The inner loop iterates over the
Y axis from bottom to top, the middle loop iterates over the Z axis from 0 to
15, and the outer loop iterates over the X axis from 15 down to 0.
To ensure that block closer to the viewer are drawn on top while blocks that
should be obstructed are drawn are hidden, the blocks are drawn one layer at a
time from bottom to top (Y=0 to Y=15) and from back to front.
.. note::
The iteration happens in ``iterate.c`` in the :c:func:`chunk_render`
function. In the code, the Y and Z axes are switched in name only. (oops)
In other words, the column of blocks at X=15, Z=0 is drawn from bottom to top.
Then the next column over on the Z axis (X=15, Z=1) is drawn, and so fourth
until the entire plane of cubes at X=15 is drawn (the upper-right face). Then it
starts with the next plane at X=14, and so fourth until the entire chunk is
drawn.
From the data file on disk, block information in a chunk is a three-dimensional
array of bytes, each representing a `block id
<http://www.minecraftwiki.net/wiki/Data_values#Block_IDs_.28Minecraft_Beta.29>`_.
The process of assembling a chunk is simply a matter of iterating over this
array, reading the blockid values, looking up the appropriate sprite, and
pasting it on the chunk image at the appropriate location.
Tile Rendering
==============