So I made PixelTool to help out!
What is PixelTool?
PixelTool is an online voxel-based tool for drawing isometric pixel art graphics. To use it you modify a 3D volume of voxels; picking 8-bit colours for each of the voxels and leaving the background as the 'magic blue' which is transparent.
It takes the voxel data and does a pixel-perfect rendering of it into 3D and adding lighting and shadowing, but still sticking to the starting 8-bit colour palette.
Slices through the voxel data of a piece of heavy hauling equipment for OpenTTD
The corresponding rendered image of the voxel block.
Blowing up the voxels in the rendered image by 4 times lets you see what is going on in a bit more detail:
PixelTool isn't just a cheap imitation of 3D rendering software, it is a dedicated tool streamlined to making isometric sprites for classic 8-bit games.
Want to play some more?
Test PixelTool out online here: http://www.richardwheeler.net/interactive/pixeltool.html
Download this example of voxel data here: www.richardwheeler.net/hosting/voxeldata.txt
Join the discussion here: http://www.tt-forums.net/viewtopic.php?f=26&t=69974&start=60