mirror of
https://github.com/DrBeef/Raze.git
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113 lines
2.3 KiB
Lua
113 lines
2.3 KiB
Lua
-- "Extended" math module for Lunatic.
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local ffi = require("ffi")
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local bit = require("bit")
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local math = require("math")
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local geom = require("geom")
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local assert = assert
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module(...)
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local BANG2RAD = math.pi/1024
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local isintab = ffi.new("int16_t [?]", 2048)
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local dsintab = ffi.new("double [?]", 2048)
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for a=0,511 do
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local s = math.sin(a*BANG2RAD)
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isintab[a] = 16384*s
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dsintab[a] = s
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end
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isintab[512] = 16384
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dsintab[512] = 1
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for i=513,1023 do
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isintab[i] = isintab[1024-i];
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dsintab[i] = dsintab[1024-i];
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end
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for i=1024,2047 do
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isintab[i] = -isintab[i-1024];
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dsintab[i] = -dsintab[i-1024];
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end
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local band = bit.band
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local function ksc_common(ang)
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ang = band(ang, 2047)
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assert(ang < 2048+0ULL) -- might have been passed NaN
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return ang
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end
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-- k{sin,cos}: 16384-scaled output, 2048-based angle input
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function ksin(ang)
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return isintab[ksc_common(ang)]
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end
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function kcos(ang)
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return isintab[ksc_common(ang+512)]
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end
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local sin, cos = math.sin, math.cos
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-- {sin,cos}b: [-1..1] output, 2048-based angle input
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function sinb(ang)
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return dsintab[ksc_common(ang)]
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end
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function cosb(ang)
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return dsintab[ksc_common(ang+512)]
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end
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-- Approximations to 2D and 3D Euclidean distances (also see common.c)
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local abs = math.abs
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local arshift = bit.arshift
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local function dist_common(pos1, pos2)
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local x = abs(pos1.x - pos2.x)
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local y = abs(pos1.y - pos2.y)
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if (x < y) then
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x, y = y, x
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end
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return x, y
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end
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function ldist(pos1, pos2)
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local x, y = dist_common(pos1, pos2)
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local t = y + arshift(y,1)
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return x - arshift(x,5) - arshift(x,7) + arshift(t,2) + arshift(t,6)
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end
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function dist(pos1, pos2)
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local x, y = dist_common(pos1, pos2)
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local z = abs(arshift(pos1.z - pos2.z, 4))
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if (x < z) then
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x, z = z, x
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end
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local t = y + z
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return x - arshift(x,4) + arshift(t,2) + arshift(t,3)
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end
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-- Point rotation. Note the different order of arguments from engine function.
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-- XXX: passing mixed vec2/vec3 is problematic. Get rid of geom.vec2?
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-- <ang>: BUILD angle (0-2047 based)
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function rotate(pos, pivot, ang)
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local p = geom.tovec3(pos)-pivot
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local c, s = cosb(ang), sinb(ang)
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local x, y = p.x, p.y
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p.x = pivot.x + (c*x - s*y)
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p.y = pivot.y + (c*y + s*x)
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return p
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end
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