PICO-8 tline() perspective demo

tline-perspective-demo.p8

pico-8 cartridge // http://www.pico-8.com
version 21
__lua__
-- basic perspective tline demo by @powersaurus

-- player rotation
a=0
-- player screen pos
px=64
py=64
mx=0
my=0
-- toggle map/map-rotated-with-tline
rotated=true

function _update()
 if btn(⬆️) then
  mx+=cos(a)/8
  my+=sin(a)/8
 end
 if btn(⬇️) then
  mx-=cos(a)/8
  my-=sin(a)/8
 
 end
 if btn(⬅️) then
  a+=3/360
 elseif btn(➡️) then
  a-=3/360
 end
 if btnp(❎) then
  rotated=not rotated
 end
 
 if(a<0)a+=1.0
 if(a>=1.0)a-=1.0
end

function _draw()
 cls(6)
 
 if rotated then
  draw_rotated()
 else
  draw_map_view()
 end
 
 print("⬅️ ➡️ rotate view",2,2,7)
 print("❎ toggle rotated view",2,10,7)
end

function draw_rotated()
 -- loop map outside of 8x8
 poke(0x5f38, 8)
	poke(0x5f39, 8)

 -- player direction
 local sty=sin(a)
 local stx=cos(a)
 
 -- camera direction
 local msy=cos(a)
 local msx=-sin(a)

 -- not bothering with
 -- 64..71 - too noisy
 for y=72,128 do  
  local dist=(128/(2*y-128+1))

  --printh(">"..msx.." "..msy)
  -- divide by smaller number to zoom in
  local dby4=dist/2
  local d16=dby4/64
  
  tline(
   0,y,127,y,
   
   mx+(-msx+stx)*dby4,
   my+(-msy+sty)*dby4,
   
   d16*msx,d16*msy
   -- after every pixel *drawn*
   -- not texel!!!!
  ) 
 end
 
	--printh("===")

 -- point in direction of players view
 --line(px,128,px,120,7)
 
end

function draw_map_view()

 map(0,0,24,24,10,10)


 draw_player()
end

function draw_player()
 local stx=-sin(a)
 local sty=cos(a)
 
 local psx=-sin(a+90/360)
 local psy=cos(a+90/360)
 
 local mmx=mx*8+24
 local mmy=my*8+24
 -- player location
 circfill(mmx,mmy,1,7)
 -- player view direction
 line(mmx,mmy,mmx+stx*8,mmy+sty*8,7)
end
__gfx__
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__map__
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