3d projection issue

Tue, 27 Nov 2018 14:46:09 UTC

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!

Tiny Sim

Thu, 19 May 2016 08:30:44 UTC

Tiny Sim 1.3

by yellowbaron

[Click to Play]

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:

If you are more the serious type, there is a 34-page flight manual, which explains everything in detail and features 20+ flight lessons.

We also created an entire area you can fly in (with a mountain, an island, ships and much more):

Just as a sneak preview, here are some of the things you can do:

Smooth landings

High speed buzzing

Illegal low-level flying at night

Instrument flying in the clouds

Here is the real cockpit on a flight in the Swiss alps to compare:

Update 1.1

fixed polygon gaps
added collision detection for wind turbines

Update 1.2

sub-pixel polygon rasterization
faster textured clouds
fixed ugly crash

Update 1.3