lerp testing

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Nov 3rd, 2021

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local function intY(a,b,y)
return a.x + ((y - a.y) * (b.x - a.x)) / (b.y - a.y)
end
--get the t value for a point (p) somewhere between the line formed from two give points (a,b)
local function getT(a,b,p)
local v1 = vector.new( a.x-b.x, a.y-b.y )
local v2 = vector.new( a.x-p.x, a.y-p.y )
return (v1:dot(v2)) / (v1:dot(v1))
end
--use the t value of a point to interpolate between two given values (v1,v2)
--for interpolating between z's, v1 = starting z value, v2 = ending z value
local function lerp(v1,v2,t)
return (1 - t) * v1 + t * v2
end
local function pPix(x,y,c)
term.setCursorPos(x,y)
term.setBackgroundColor(colors.white)
term.setTextColor(colors.black)
term.write(c)
term.setBackgroundColor(colors.black)
term.setTextColor(colors.white)
end
local function fill(a,b,c)
if a.y < b.y then a,b = b,a end
if a.y < c.y then a,c = c,a end
if b.x > c.x then b,c = c,b end
for y = b.y, a.y-1 do
local xStart = intY(a,b,y)
local xEnd = intY(a,c,y)
local p1 = vector.new(xStart,y)
local p2 = vector.new(xEnd,y)
local t1 = getT(a,b,p1)
local t2 = getT(a,c,p2)
local z1 = lerp(a.z,b.z,t1)
local z2 = lerp(a.z,c.z,t2)
for x = xStart, xEnd do
local t3 = (x - xStart) / (xEnd - xStart)
local z = math.floor(lerp(z1,z2,t3))
pPix(x,y,z)
end
end
end
local a = vector.new(20,20,9)
local b = vector.new(2,2,1)
local c = vector.new(30,2,4)
term.clear()
fill(a,b,c)

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