yellowbaron

3d projection issue

yellowbaron

BBS

PICO-8 Workshop

:: Unfold ::

Hi,
I would like to add a basic 3d outside view to my flight sim project Tiny Sim. For this I started with the code below, which is just showing a simplified runway (essentially, a rectangle with some points). I am trying to get the projection function right and while it works for z<0 it fails miserably for z>=0: the runway is somehow mirrored in the upper half of the screen.

rwy = {{{-1,0,0}, --points
        {-1,0,30},
        {1,0,30},
        {1,0,0}},
       {{1,2}, --lines
        {2,3},
        {3,4},
        {4,1}},
         4}

cam = {0,1,-4}
mult = 64
sp = 0.01

function _update()
  if btn(0) then cam[1] -= 0.1 end
  if btn(1) then cam[1] += 0.1 end
  if btn(2) then cam[2] += 0.1 end
  if btn(3) then cam[2] -= 0.1 end
  if(cam[2]<0) cam[2]=0
  if btn(4) then cam[3] -= 0.1 end
  if btn(5) then cam[3] += 0.1 end
end

function _draw()
  cls()
  print("x="..cam[1],0,6*1)
  print("y="..cam[2],0,6*2) 
  print("z="..cam[3],0,6*3) 

  draw_shape(rwy)
  for i=1, 14 do
    draw_point({0,0,i*2},7)
  end
  draw_point({-0.5,0,2},7)
  draw_point({0.5,0,2},7)
end

function draw_shape(s,c)
  for l in all(s[2]) do
    draw_line(s[1][l[1]], s[1][l[2]], c)
  end
end

function draw_line(p1,p2,c)
  x0, y0 = project(p1)
  x1, y1 = project(p2)
  line(x0, y0, x1, y1, c or 6)
end

function draw_point(p,c)
  x, y = project(p)
  pset(x, y, c or 11)
end

function project(p)
  x = (p[1]-cam[1])*mult/(p[3]-cam[3]) + 127/2
  y = -(p[2]-cam[2])*mult/(p[3]-cam[3]) + 127/2  
  return x, y
end

--functions for roll, pitch and yaw

Runway being displayed correctly (z<0):

Runway with wrong projection (z>=0):

I split up the projection function for z<0 and z>=0 but did not find the right formula for z>=0 yet:

function project(p)
  if cam[3]<=0 then
    x = (p[1]-cam[1])*mult/(p[3]-cam[3]) + 127/2
    y = -(p[2]-cam[2])*mult/(p[3]-cam[3]) + 127/2
  else
    x = (p[1]+cam[1])*mult/(p[3]+cam[3]) + 127/2
    y = -(p[2]+cam[2])*mult/(p[3]+cam[3]) + 127/2
  end  
  return x, y
end

Any help is much appreciated!

3d flightsim

P#59388 2018-11-27 14:46

yellowbaron

:: Unfold ::

by yellowbaron

Cart #tenkizoti-4 | 2020-04-10 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA

Hi Aviator!

This is a tiny flight simulator based on a Cessna-172R with a G1000 glass cockpit. (This is the plane I fly in real life, so I thought it would be a challenge to see if it can be done with Pico-8.)

The flight model is not based on theory but on my observations as a pilot. I have to say that it's quite good ;-) Within the limits of Pico-8 it quite feels like the real thing.

Disclaimer: while I created the instruments and the flight model, the majority of the programming work was done by @freds72, including 3D outside view, code structure, eye candy, music, etc. Many thanks Fred, this would not have been possible without your ninja programming skills!!

If you want to go flying right away, the cheatsheet will get you in the air in less than 1 minute: