body.lua

body.lua

-- title:  ModelRenderer
-- author: FlamingPandas
-- desc:   Shows 3D models
-- script: lua


point={x=0,y=0,z=300}


fov=100  --  Field of View
rspeed=.1  --  Rotation speed, you can change it 
tspeed=10  --  Translation speed, you can change it

mesh={}  --  Table that contains all the 3D points
polygon={}  -- Table that contains all conections of 3D points to create triangle polygons, with their texture specified too
zorder={}  --  Tabe used to know the rendering order of the triangles


function addMesh(mx,my,mz)
    local m={x=mx,y=my,z=mz,u=0,v=0}
    table.insert(mesh,m)
end


function addPolygon( pp1,pp2,pp3,
                     pu1,pv1,pu2,
                     pv2,pu3,pv3  )

    local p={  p1=pp1,p2=pp2,p3=pp3,
               u1=pu1,v1=pv1,u2=pu2,
               v2=pv2,u3=pu3,v3=pv3, zOrd=0  }
    table.insert(polygon,p)
end


function addZOrder(polygon,zor)
    local z={poly=polygon,zo=zor}
    table.insert(zorder,z)
end


function init()
    --  "Loading" points and polygon data
    local m=addMesh

    m(5,20,5)  -- 1
    m(-5,20,5)  -- 2
    m(-5,20,-5)  -- 3
    m(5,20,-5)  -- 4

    m(5,0,5)  -- 5
    m(-5,0,5)  -- 6
    m(-5,0,-5)  --7
    m(5,0,-5)  -- 8


    local p=addPolygon
    p(1,2,3, 48,8,64,8,64,14)
    p(1,3,4, 48,8,64,8,64,14)

    p(1,5,2, 0,7,16,7,16,16)
    p(5,6,2, 0,7,16,7,16,16)

    p(6,7,2, 0,7,16,7,16,16)
    p(2,7,3, 0,7,16,7,16,16)


    p(4,3,7, 48,8,64,8,64,14)
    p(4,7,8, 48,8,64,8,64,14)

    p(1,4,5, 0,7,16,7,16,16)
    p(5,4,8, 0,7,16,7,16,16)


    p(5,7,6, 0,7,16,7,16,16)
    p(5,8,7, 0,7,16,7,16,16)

    for i,p in pairs(polygon) do
     addZOrder(i,0)
    end
end

init()
mode=1


function TIC()
    if btn(6) then
        if btn(0) then translate(0,-tspeed,0) end
        if btn(1) then translate(0,tspeed,0) end
        if btn(2) then translate(-tspeed,0,0) end
        if btn(3) then translate(tspeed,0,0) end
    else
        if btn(0) then rotatateX(-rspeed) end
        if btn(1) then rotatateX(rspeed) end
        if btn(2) then rotatateY(-rspeed) end
        if btn(3) then rotatateY(rspeed) end
    end
        if btn(4) then if fov<800 then fov=fov+10 end end
        if btn(5) then if fov>10 then fov=fov-10 end end
        if btnp(7) then if mode<3 then mode=mode+1 else mode=1 end end
    cls(13)

    -- Shows info from the zorder table
    -- for i,z in pairs(zorder) do
    --   print(z.poly.." - "..z.zo,10,10*i)
    -- end
    calculateMeshUV()
    calculateZOrder()
    table.sort(zorder,function(a,b) return a.zo > b.zo end)

    if mode==1 then showMesh() end
    if mode==2 then    showWireFrame() end
    if mode==3 then showMesh() showWireFrame() end
end


--Given this 3D points calculate how they would look in a 2D screen
function calculateMeshUV()
    for i,m in pairs(mesh) do
        m.u=((m.x+point.x)*(fov/(m.z+point.z)))+120
        m.v=((m.y+point.y)*(fov/(m.z+point.z)))+70
    end
end


-- I made this up but ot works... it gives the avarage of the depth of the three points of each triangle, it works good enough to know witch triangles to draw first (the further ones)
function calculateZOrder()
    m=mesh
    for i,p in pairs(polygon) do
        p.zord=(m[p.p1].z+m[p.p2].z+m[p.p3].z)/3
        updateZOrder(i,p.zord)
    end
end


-- Once calcuated the zorder you need to update the zorder table with those values
-- Why do we need this values in another table? well... lua can sort this table and now we have the order in witch to draw the triangles
function updateZOrder(polygon,zor)
    for i,z in pairs(zorder) do
        if z.poly==polygon then
            z.zo=zor
        end
    end
end


-- Using the textri function you can show triangles with textures
-- This function draws all triangles that are facimg the camera with the textures defined on the init function
-- The function draws them in the zorder from further to closest so when a triangle is closer it shows "Above" othee triangles
function showMesh()
    m=mesh
    for i,z in pairs(zorder) do
        p=polygon[z.poly]
        -- If the triangle points are clockwise they are facing the camera
        if isClockWise(p) then
            --Draw the textured triangle    textri()
            tri( m[p.p1].u  ,m[p.p1].v,
            m[p.p2].u,  m[p.p2].v,
            m[p.p3].u,  m[p.p3].v,  0 )
            -- p.u1,p.v1,p.u2,p.v2,p.u3,p.v3)
        end
    end
end


-- Given a triangle return true if it's points are clockwise false if they aren't
function isClockWise(poly)
    p=poly
    m=mesh
    return (m[p.p2].v-m[p.p1].v)*
           (m[p.p3].u-m[p.p2].u)-
           (m[p.p3].v-m[p.p2].v)*
           (m[p.p2].u-m[p.p1].u) > 0
end


--Function that draws all lines in the three points of a triangle (it just shpws the WireFrame and also the individual points)
function showWireFrame()
    m=mesh
    for i,p in pairs(polygon) do
        line(m[p.p1].u,m[p.p1].v,m[p.p2].u,m[p.p2].v,15)
        line(m[p.p2].u,m[p.p2].v,m[p.p3].u,m[p.p3].v,15)
        line(m[p.p3].u,m[p.p3].v,m[p.p1].u,m[p.p1].v,15)
    end

    for i,m in pairs(mesh) do
     circ(m.u,m.v,1,0)
     print(i,m.u,m.v+5,3)
    end
end


-- Rotates all pf the points in the mesh by an angle in the x axes
function rotatateX(angle)
    cos=math.cos(angle)
    sin=math.sin(angle)
    for i,p in pairs(mesh) do
        y=p.y*cos-p.z*sin
        z=p.z*cos+p.y*sin
        p.y=y
        p.z=z
    end
end


function rotatateY(angle)
    cos=math.cos(angle)
    sin=math.sin(angle)
    for i,p in pairs(mesh) do
        x=p.x*cos-p.z*sin
        z=p.z*cos+p.x*sin
        p.x=x
        p.z=z
    end
end


function rotatateZ(angle)
    cos=math.cos(angle)
    sin=math.sin(angle)
    for i,p in pairs(mesh) do
        x=p.x*cos-p.y*sin
        y=p.y*cos+p.x*sin
        p.x=x
        p.y=y
    end
end


-- Translate all of the points an x,y and z distance
function translate(dx,dy,dz)
    point.x=point.x+dx
    point.y=point.y+dy
    point.z=point.z+dz
end