86 lines
3.4 KiB
Markdown
86 lines
3.4 KiB
Markdown
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# FAQ
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### How to run it?
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There's no GUI. Find a directory with Minecraft Anvil files (.mca).
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Copy a Minecraft "terrain.png" into that directory (do a google
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image search). Run from that directory.
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### How accurate is this as a Minecraft viewer?
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Not very. Many Minecraft blocks are not handled correctly:
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* No redstone, rails, or other "flat" blocks
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* No signs, doors, fences, carpets, or other complicated geometry
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* Stairs are turned into ramps
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* Upper slabs turn into lower slabs
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* Wood types only for blocks, not stairs, slabs, etc
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* Colored glass becomes regular glass
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* Glass panes become glass blocks
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* Water is opaque
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* Water level is incorrect
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* No biome coloration
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* Cactus is not shrunk, shows holes
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* Chests are not shrunk
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* Double-chests draw as two chests
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* Pumpkins etc. are not rotated properly
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* Torches are drawn hackily, do not attach to walls
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* Incorrect textures for blocks that postdate terrain.png
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* Transparent textures have black fringes due to non-premultiplied-alpha
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* Skylight and block light are combined in a single value
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* Only blocks at y=1..255 are shown (not y=0)
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* If a 32x32x256 "quad-chunk" needs more than 800K quads, isn't handled (very unlikely)
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Some of these are due to engine limitations, and some of
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these are because I didn't make the effort since my
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goal was to make a demo for stb_voxel_render.h, not
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to make a proper Minecraft viewer.
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### Could this be turned into a proper Minecraft viewer?
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Yes and no. Yes, you could do it, but no, it wouldn't
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really resemble this code that much anymore.
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You could certainly use this engine to
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render the parts of Minecraft it works for, but many
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of the things it doesn't handle it can't handle at all
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(stairs, water, fences, carpets, etc) because it uses
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low-precision coordinates to store voxel data.
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You would have to render all of the stuff it doesn't
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handle through another rendering path. In a game (not
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a viewer) you would need such a path for movable entities
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like doors and carts anyway, so possibly handling other
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things that way wouldn't be so bad.
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Rails, ladders, and redstone lines could be implemented by
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using tex2 to overlay those effects, but you can't rotate
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tex1 and tex2 independently, so there may be cases where
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the underlying texture needs a different rotation from the
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overlaid texture, which would require separate rendering.
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Handling redstone's brightness being different from underlying
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block's brightness would require separate rendering.
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You can use the face-color effect to do biome coloration,
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but the change won't be smooth the way it is in Minecraft.
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### Why isn't building the mesh data faster?
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Partly because converting from minecraft data is expensive.
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Here is the approximate breakdown of an older version
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of this executable and lib that did the building single-threaded.
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* 25% loading & parsing minecraft files (4/5ths of this is my crappy zlib)
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* 18% converting from minecraft blockids & lighting to stb blockids & lighting
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* 10% reordering from data[z][y]\[x] (minecraft-style) to data[y][x]\[z] (stb-style)
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* 40% building mesh data
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* 7% uploading mesh data to OpenGL
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I did do significant optimizations after the above, so the
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final breakdown is different, but it should give you some
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sense of the costs.
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