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-- Color palette. | |
pal({131,3,139,11,138},1) | |
-- Set dither pattern. | |
-- `▒` is a global variable inserted by PICO-8 that has the value 23130.5. | |
-- The value corresponds to a fillp pattern that looks like the glyph itself. | |
-- We need to floor ▒ to remove the .5, which signifies the pattern should be transparent. | |
-- (`\` is PICO-8's integer divison operator. So `x\1` floors the left operand.) | |
fillp(▒\1) | |
-- Get a random number. Passing -1 will generate nearly any PICO-8 number. | |
r=rnd(-1) | |
-- Make short alias for sin. | |
f=sin | |
-- Render 151 frames. | |
-- Once this loop ends, we call `run()` to restart the application, which will | |
-- generate a new point of view thanks the previous `rnd` call. | |
for i=0,150 do | |
-- Camera rotation. Use random initial offset and increase over time. | |
-- ▤ is a PICO-8 global with the value 3855.5. | |
a=r+i/▤ | |
-- To maximise performance need to use local variables rather than globals. | |
-- (Globals use a table lookup.) | |
-- `c` and `s` save the `cos(a)` and `sin(a)` values. | |
-- `u` and `v` will be used for world space coordinates. | |
-- `h` will be used for terrain height. | |
local c,s,u,v,h = cos(a),f(a) | |
-- Iterate pixels on the screen. | |
-- Each pixel will be transformed into world space, and we'll draw each point | |
-- as a section of terrain. | |
-- | |
-- Note we extend past the bottom of the screen to ensure we render terrain | |
-- that originates from below the screen and is still visible. | |
for y=4,156 do | |
-- It's not possible to render 152*127 points in one frame, so we split them | |
-- over 6 frames. We render every 6th column, and change the offset by 1 | |
-- every frame. | |
-- This causes some ghosting, but a slow camera hides most of it. | |
-- (This also causes the nice Windows Movie Maker transition between runs!) | |
for x=i%6,127,6 do | |
-- Convert screen space to world space (orthographic). | |
-- Note: x/5-13 ≈≈ (x-64)/5 (tilts the camera up) | |
u=x/5-13 | |
v=y-90 | |
u,v = (c*u - s*v+r)/5,(s*u + c*v)/5 -- Rotate and scale! | |
-- Get terrain height from world (u, v). | |
-- I found that frequency-modulation (using sin inside of sin) was a nice | |
-- simple way to get varied terrain. | |
-- The `3.2` was chosen so that `h` can be used directly as a color value. | |
h=3.2 | |
+f(u/8 + f(u/9 - v/7)/3) | |
+f(u/8 - v/9 + f(v/7)/3) | |
-- Draw terrain point as vertical line. | |
-- `h + .5` is the first dithered color value (offset by half). | |
-- `h\1*16` is the second ditherd color value (shift right by 2 and no offset). | |
-- Note: h\1*16 == (h\1)*16 == flr(h)*16 | |
line( | |
x, y, | |
x, y - h*7, | |
h + .5 + h\1*16 | |
) | |
end | |
end | |
flip() | |
end | |
run() |
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