Computer Science Canada

Help with 3D
Author:  Lucas [ Sun Mar 20, 2011 2:11 pm ]
Post subject:  Help with 3D
What is it you are trying to achieve?
wrote a code that lets me rotate 'LUC' on X, Y, and Z axis, but its a wire frame and i would like to able to draw the faces of the objects


What is the problem you are having?
dont know how to tell what faces of the objects i can 'see' and which ones i cant


Describe what you have tried to solve this problem
tried a couple of different techniques


Post any relevant code (You may choose to attach the file instead of posting the code if it is too long)


Turing:


setscreen ("graphics: 800; 600")
setscreen ("offscreenonly")
var points : int := 44
var ox, oy : int
var x, y, z, tx, tz, ty, xr, yr, zr : array 1 .. points of real
var dx, dy : array 1 .. points of int
var Vx : real := 0
var Vy : real := -850
var Vz : real := 0
var direction : int
var move : string (1)

procedure initialvalues
    % "L"
    x (1) := -1
    y (1) := 50
    z (1) := 200
    x (2) := -1
    y (2) := -50
    z (2) := 200
    x (3) := -100
    y (3) := -50
    z (3) := 200
    x (4) := -100
    y (4) := 50
    z (4) := 200
    x (5) := -1
    y (5) := 50
    z (5) := 1
    x (6) := -1
    y (6) := -50
    z (6) := 1
    x (7) := -100
    y (7) := -50
    z (7) := -100
    x (8) := -100
    y (8) := 50
    z (8) := -100
    x (9) := 100
    y (9) := 50
    z (9) := 1
    x (10) := 100
    y (10) := -50
    z (10) := 1
    x (11) := 100
    y (11) := -50
    z (11) := -100
    x (12) := 100
    y (12) := 50
    z (12) := -100
    % "U"
    x (13) := 300
    y (13) := 50
    z (13) := 200
    x (14) := 300
    y (14) := -50
    z (14) := 200
    x (15) := 200
    y (15) := -50
    z (15) := 200
    x (16) := 200
    y (16) := 50
    z (16) := 200
    x (17) := 300
    y (17) := 50
    z (17) := 1
    x (18) := 300
    y (18) := -50
    z (18) := 1
    x (19) := 200
    y (19) := -50
    z (19) := -100
    x (20) := 200
    y (20) := 50
    z (20) := -100
    x (21) := 500
    y (21) := 50
    z (21) := -100
    x (22) := 500
    y (22) := -50
    z (22) := -100
    x (23) := 400
    y (23) := -50
    z (23) := 1
    x (24) := 400
    y (24) := 50
    z (24) := 1
    x (25) := 500
    y (25) := 50
    z (25) := 200
    x (26) := 500
    y (26) := -50
    z (26) := 200
    x (27) := 400
    y (27) := -50
    z (27) := 200
    x (28) := 400
    y (28) := 50
    z (28) := 200
    % "C"
    x (29) := 800
    y (29) := 50
    z (29) := 200
    x (30) := 800
    y (30) := -50
    z (30) := 200
    x (31) := 800
    y (31) := -50
    z (31) := 100
    x (32) := 800
    y (32) := 50
    z (32) := 100
    x (33) := 700
    y (33) := 50
    z (33) := 100
    x (34) := 700
    y (34) := -50
    z (34) := 100
    x (35) := 600
    y (35) := -50
    z (35) := 200
    x (36) := 600
    y (36) := 50
    z (36) := 200
    x (37) := 700
    y (37) := 50
    z (37) := 1
    x (38) := 700
    y (38) := -50
    z (38) := 1
    x (39) := 600
    y (39) := -50
    z (39) := -100
    x (40) := 600
    y (40) := 50
    z (40) := -100
    x (41) := 800
    y (41) := 50
    z (41) := 1
    x (42) := 800
    y (42) := -50
    z (42) := 1
    x (43) := 800
    y (43) := -50
    z (43) := -100
    x (44) := 800
    y (44) := 50
    z (44) := -100
    ox := maxx div 2
    oy := maxy div 2
    for a : 1 .. points
        x (a) := x (a) - 350
        if x (a) > -1 and y (a) > 0 then
            tx (a) := arctand (x (a) / y (a))
        elsif x (a) > 0 and y (a) < 1 then
            tx (a) := (-90 - arctand (y (a) / x (a))) + 180
        elsif x (a) < 1 and y (a) < 0 then
            tx (a) := arctand (x (a) / y (a)) + 180
        else
            tx (a) := (-90 - arctand (y (a) / x (a))) + 360
        end if
        if x (a) > -1 and z (a) > 0 then
            ty (a) := arctand (x (a) / z (a))
        elsif x (a) > 0 and z (a) < 1 then
            ty (a) := (-90 - arctand (z (a) / x (a))) + 180
        elsif x (a) < 1 and z (a) < 0 then
            ty (a) := arctand (x (a) / z (a)) + 180
        else
            ty (a) := (-90 - arctand (z (a) / x (a))) + 360
        end if
        if y (a) > -1 and z (a) > 0 then
            tz (a) := arctand (y (a) / z (a))
        elsif y (a) > 0 and z (a) < 1 then
            tz (a) := (-90 - arctand (z (a) / y (a))) + 180
        elsif y (a) < 1 and z (a) < 0 then
            tz (a) := arctand (y (a) / z (a)) + 180
        else
            tz (a) := (-90 - arctand (z (a) / y (a))) + 360
        end if
        xr (a) := sqrt ((x (a) ** 2) + (y (a) ** 2))
        yr (a) := sqrt ((x (a) ** 2) + (z (a) ** 2))
        zr (a) := sqrt ((z (a) ** 2) + (y (a) ** 2))
        dx (a) := (((100 / (y (a) - Vy + 100)) * (x (a) - Vx)) + Vx) div 1
        dy (a) := (((100 / (y (a) - Vy + 100)) * (z (a) - Vz)) + Vz) div 1
    end for
end initialvalues

procedure draw
    for a : 1 .. points
        dx (a) := (((200 / (y (a) - Vy + 200)) * (x (a) - Vx)) + Vx) div 1
        dy (a) := (((200 / (y (a) - Vy + 200)) * (z (a) - Vz)) + Vz) div 1
        %drawfilloval (dx (a) + ox, dy (a) + oy, 1, 1, red)
    end for
    % "L"
    drawline (dx (1) + ox, dy (1) + oy, dx (2) + ox, dy (2) + oy, red)
    drawline (dx (2) + ox, dy (2) + oy, dx (3) + ox, dy (3) + oy, red)
    drawline (dx (3) + ox, dy (3) + oy, dx (4) + ox, dy (4) + oy, red)
    drawline (dx (4) + ox, dy (4) + oy, dx (1) + ox, dy (1) + oy, red)
    drawline (dx (5) + ox, dy (5) + oy, dx (6) + ox, dy (6) + oy, red)
    drawline (dx (7) + ox, dy (7) + oy, dx (8) + ox, dy (8) + oy, red)
    drawline (dx (9) + ox, dy (9) + oy, dx (10) + ox, dy (10) + oy, red)
    drawline (dx (10) + ox, dy (10) + oy, dx (11) + ox, dy (11) + oy, red)
    drawline (dx (11) + ox, dy (11) + oy, dx (12) + ox, dy (12) + oy, red)
    drawline (dx (12) + ox, dy (12) + oy, dx (9) + ox, dy (9) + oy, red)
    drawline (dx (1) + ox, dy (1) + oy, dx (5) + ox, dy (5) + oy, red)
    drawline (dx (2) + ox, dy (2) + oy, dx (6) + ox, dy (6) + oy, red)
    drawline (dx (3) + ox, dy (3) + oy, dx (7) + ox, dy (7) + oy, red)
    drawline (dx (4) + ox, dy (4) + oy, dx (8) + ox, dy (8) + oy, red)
    drawline (dx (5) + ox, dy (5) + oy, dx (9) + ox, dy (9) + oy, red)
    drawline (dx (6) + ox, dy (6) + oy, dx (10) + ox, dy (10) + oy, red)
    drawline (dx (7) + ox, dy (7) + oy, dx (11) + ox, dy (11) + oy, red)
    drawline (dx (8) + ox, dy (8) + oy, dx (12) + ox, dy (12) + oy, red)
    % "U"
    drawline (dx (13) + ox, dy (13) + oy, dx (14) + ox, dy (14) + oy, red)
    drawline (dx (14) + ox, dy (14) + oy, dx (15) + ox, dy (15) + oy, red)
    drawline (dx (15) + ox, dy (15) + oy, dx (16) + ox, dy (16) + oy, red)
    drawline (dx (16) + ox, dy (16) + oy, dx (13) + ox, dy (13) + oy, red)
    drawline (dx (17) + ox, dy (17) + oy, dx (18) + ox, dy (18) + oy, red)
    drawline (dx (19) + ox, dy (19) + oy, dx (20) + ox, dy (20) + oy, red)
    drawline (dx (21) + ox, dy (21) + oy, dx (22) + ox, dy (22) + oy, red)
    drawline (dx (23) + ox, dy (23) + oy, dx (24) + ox, dy (24) + oy, red)
    drawline (dx (25) + ox, dy (25) + oy, dx (26) + ox, dy (26) + oy, red)
    drawline (dx (26) + ox, dy (26) + oy, dx (27) + ox, dy (27) + oy, red)
    drawline (dx (27) + ox, dy (27) + oy, dx (28) + ox, dy (28) + oy, red)
    drawline (dx (28) + ox, dy (28) + oy, dx (25) + ox, dy (25) + oy, red)
    drawline (dx (13) + ox, dy (13) + oy, dx (17) + ox, dy (17) + oy, red)
    drawline (dx (14) + ox, dy (14) + oy, dx (18) + ox, dy (18) + oy, red)
    drawline (dx (15) + ox, dy (15) + oy, dx (19) + ox, dy (19) + oy, red)
    drawline (dx (16) + ox, dy (16) + oy, dx (20) + ox, dy (20) + oy, red)
    drawline (dx (17) + ox, dy (17) + oy, dx (24) + ox, dy (24) + oy, red)
    drawline (dx (18) + ox, dy (18) + oy, dx (23) + ox, dy (23) + oy, red)
    drawline (dx (19) + ox, dy (19) + oy, dx (22) + ox, dy (22) + oy, red)
    drawline (dx (20) + ox, dy (20) + oy, dx (21) + ox, dy (21) + oy, red)
    drawline (dx (21) + ox, dy (21) + oy, dx (25) + ox, dy (25) + oy, red)
    drawline (dx (22) + ox, dy (22) + oy, dx (26) + ox, dy (26) + oy, red)
    drawline (dx (23) + ox, dy (23) + oy, dx (27) + ox, dy (27) + oy, red)
    drawline (dx (24) + ox, dy (24) + oy, dx (28) + ox, dy (28) + oy, red)
    % "C"
    drawline (dx (29) + ox, dy (29) + oy, dx (30) + ox, dy (30) + oy, red)
    drawline (dx (30) + ox, dy (30) + oy, dx (31) + ox, dy (31) + oy, red)
    drawline (dx (31) + ox, dy (31) + oy, dx (32) + ox, dy (32) + oy, red)
    drawline (dx (32) + ox, dy (32) + oy, dx (29) + ox, dy (29) + oy, red)
    drawline (dx (33) + ox, dy (33) + oy, dx (34) + ox, dy (34) + oy, red)
    drawline (dx (35) + ox, dy (35) + oy, dx (36) + ox, dy (36) + oy, red)
    drawline (dx (37) + ox, dy (37) + oy, dx (38) + ox, dy (38) + oy, red)
    drawline (dx (39) + ox, dy (39) + oy, dx (40) + ox, dy (40) + oy, red)
    drawline (dx (41) + ox, dy (41) + oy, dx (42) + ox, dy (42) + oy, red)
    drawline (dx (42) + ox, dy (42) + oy, dx (43) + ox, dy (43) + oy, red)
    drawline (dx (43) + ox, dy (43) + oy, dx (44) + ox, dy (44) + oy, red)
    drawline (dx (44) + ox, dy (44) + oy, dx (41) + ox, dy (41) + oy, red)
    drawline (dx (29) + ox, dy (29) + oy, dx (36) + ox, dy (36) + oy, red)
    drawline (dx (30) + ox, dy (30) + oy, dx (35) + ox, dy (35) + oy, red)
    drawline (dx (31) + ox, dy (31) + oy, dx (34) + ox, dy (34) + oy, red)
    drawline (dx (32) + ox, dy (32) + oy, dx (33) + ox, dy (33) + oy, red)
    drawline (dx (33) + ox, dy (33) + oy, dx (37) + ox, dy (37) + oy, red)
    drawline (dx (34) + ox, dy (34) + oy, dx (38) + ox, dy (38) + oy, red)
    drawline (dx (35) + ox, dy (35) + oy, dx (39) + ox, dy (39) + oy, red)
    drawline (dx (36) + ox, dy (36) + oy, dx (40) + ox, dy (40) + oy, red)
    drawline (dx (37) + ox, dy (37) + oy, dx (41) + ox, dy (41) + oy, red)
    drawline (dx (38) + ox, dy (38) + oy, dx (42) + ox, dy (42) + oy, red)
    drawline (dx (39) + ox, dy (39) + oy, dx (43) + ox, dy (43) + oy, red)
    drawline (dx (40) + ox, dy (40) + oy, dx (44) + ox, dy (44) + oy, red)
end draw
procedure rotateX
    for a : 1 .. points
        xr (a) := sqrt ((x (a) ** 2) + (y (a) ** 2))
        if x (a) > -1 and y (a) > 0 then
            tx (a) := arctand (x (a) / y (a))
        elsif x (a) > 0 and y (a) < 1 then
            tx (a) := (-90 - arctand (y (a) / x (a))) + 180
        elsif x (a) < 1 and y (a) < 0 then
            tx (a) := arctand (x (a) / y (a)) + 180
        else
            tx (a) := (-90 - arctand (y (a) / x (a))) + 360
        end if
    end for
    for a : 1 .. 30
        for b : 1 .. points
            tx (b) := tx (b) + direction
            x (b) := sind (tx (b)) * xr (b)
            y (b) := cosd (tx (b)) * xr (b)
        end for
        draw
        View.Update
        delay (20)
        cls
    end for
end rotateX
procedure rotateY
    for a : 1 .. points
        yr (a) := sqrt ((x (a) ** 2) + (z (a) ** 2))
        if x (a) > -1 and z (a) > 0 then
            ty (a) := arctand (x (a) / z (a))
        elsif x (a) > 0 and z (a) < 1 then
            ty (a) := (-90 - arctand (z (a) / x (a))) + 180
        elsif x (a) < 1 and z (a) < 0 then
            ty (a) := arctand (x (a) / z (a)) + 180
        else
            ty (a) := (-90 - arctand (z (a) / x (a))) + 360
        end if
    end for
    for a : 1 .. 30
        for b : 1 .. points
            ty (b) := ty (b) + direction
            x (b) := sind (ty (b)) * yr (b)
            z (b) := cosd (ty (b)) * yr (b)
        end for
        draw
        View.Update
        delay (20)
        cls
    end for
end rotateY
procedure rotateZ
    for a : 1 .. points
        zr (a) := sqrt ((z (a) ** 2) + (y (a) ** 2))
        if y (a) > -1 and z (a) > 0 then
            tz (a) := arctand (y (a) / z (a))
        elsif y (a) > 0 and z (a) < 1 then
            tz (a) := (-90 - arctand (z (a) / y (a))) + 180
        elsif y (a) < 1 and z (a) < 0 then
            tz (a) := arctand (y (a) / z (a)) + 180
        else
            tz (a) := (-90 - arctand (z (a) / y (a))) + 360
        end if
    end for
    for a : 1 .. 30
        for b : 1 .. points
            tz (b) := tz (b) + direction
            y (b) := sind (tz (b)) * zr (b)
            z (b) := cosd (tz (b)) * zr (b)
        end for
        draw
        View.Update
        delay (20)
        cls
    end for
end rotateZ



initialvalues
loop
    getch (move)
    if move = "d" then
        direction := 3
        rotateX
    elsif move = "a" then
        direction := -3
        rotateX
    elsif move = "w" then
        direction := 3
        rotateZ
    elsif move = "s" then
        direction := -3
        rotateZ
    elsif move = "e" then
        direction := 3
        rotateY
    elsif move = "q" then
        direction := -3
        rotateY
    end if
end loop




Please specify what version of Turing you are using
4.1.1
Author:  Raknarg [ Mon Mar 21, 2011 9:35 am ]
Post subject:  RE:Help with 3D
I have an idea. Im not sure if it would work, but you could try.

So if you use the Draw.FillPolygon feature, you could basically set the point of all your corners and draw them that way.

So for your program you would just use a polygon for all the faces on your shape.

However theres one issue. You would need a separate array for every face. If you try to draw it with a compund array (which is way simpler) such as array 1 .. 5, 1 .. 5, its not usable for Draw.FillPolygon.

Other-wise, you could put a point for every single dot and draw faces like that.

This means it would require a rediculous amount of code (like Hunters Light Wars 1.0).
But its still possible.

Those are the only 2 ways I can think of of having a 3D picture that isn't wire-frame in turing.

I would suggest looking up that old 3D Hangman game from before though. It has o head thatb is wire-frame like yours but it also has coloured faces.
Author:  Raknarg [ Mon Mar 21, 2011 10:35 am ]
Post subject:  RE:Help with 3D
Oh, i have one other way.
In the past, I've used a bunch of lines to simulate a polygon. What you can do is for every face, you have a for loop. The line would begin at one corner and continue in a circular fashion until it fills the whole polygon.
Author:  DemonWasp [ Mon Mar 21, 2011 11:34 am ]
Post subject:  RE:Help with 3D
To actually answer the OP's question:

For each pixel, the face you can "see" at that pixel is the closest one that actually draws to that pixel.

There are a few ways to tackle the problem.

First, you could draw all the faces from back-to-front. This would require a global sort of all faces. This also faces the issue that in some cases a small polygon that should appear behind a larger polygon actually appears in front, because distances are measured from the camera to the middle of the polygon.

Second, you could draw to a buffer and keep track of the "depth", or z-value, of each pixel. This is what a graphics card does when using DirectX or OpenGL (roughly). While this does fix the problem described in the first method, it also introduces the unfortunate performance problem that you need to calculate a distance for each pixel, at each frame. This gets prohibitively slow with Turing (or any language -- generally, this is done on the graphics card, not the CPU -- but particularly Turing is bad).

Third, you could pretend to draw faces by just not drawing edges / vertices that are occluded by forward points. The easiest way to do that would be to "shoot" a ray from the camera to each vertex in an object. Calculate the intersections between that ray and your object (see: http://www.cs.princeton.edu/courses/archive/fall00/cs426/lectures/raycast/sld016.htm ). If there are any intersections which are closer to the camera than that vertex, then you should NOT draw that vertex (this is usually called "culling").

The third option should perform reasonably well, give the vague illusion of having filled volume, and won't suffer the problem in the first solution. However, it is both the least fulfilling in terms of drawing a 3D image, and possibly relatively complex.
Author:  Lucas [ Mon Mar 21, 2011 7:52 pm ]
Post subject:  RE:Help with 3D
Raknarg - that would draw every face, not the ones i can "see" Smile
DemonWasp - thx, ill try the third one, pretty sure ill understand it Smile

idea though: calculate the average depth of each face, and then draw the polygons in order of the ones furthest back first?
Author:  DemonWasp [ Mon Mar 21, 2011 8:54 pm ]
Post subject:  RE:Help with 3D
Your idea is listed as the first solution in my previous post.

However, no matter how you calculate the "average depth" of a face, there's a way for a face that SHOULD appear behind it to appear in front instead. Additionally, that method doesn't handle the case where two polygons go right through each other (though neither does my third solution).
Author:  copthesaint [ Tue Mar 22, 2011 11:17 am ]
Post subject:  Re: Help with 3D
Heres an example of a crappy buffer I made in the last 20 min, sorry for no commenting but I think this will help you.


Turing:
class buff
    export add, update, draw
    var xVal, yVal, xVal2, yVal2, dVal, clr : flexible array 0 .. -1 of int
    var xSortVal, ySortVal, xSortVal2, ySortVal2, clrSort, dSortVal : flexible array 0 .. -1 of int
    var upBound, maxBound : int := -1
    var upBoundSort, maxBoundSort : int := -1
    proc add (x : int, y : int, x2 : int, y2 : int, d : int, c : int)
        if upBound = maxBound then
            maxBound := maxBound + 1
            new xVal, maxBound
            new yVal, maxBound
            new xVal2, maxBound
            new yVal2, maxBound
            new clr, maxBound
            new dVal, maxBound
        end if
        upBound := upBound + 1
        xVal (upBound) := x
        yVal (upBound) := y
        xVal2 (upBound) := x2
        yVal2 (upBound) := y2
        clr (upBound) := c
        dVal (upBound) := d
    end add

    proc remove (i : int)
        xVal (i) := xVal (upBound)
        yVal (i) := yVal (upBound)
        xVal2 (i) := xVal2 (upBound)
        yVal2 (i) := yVal2 (upBound)
        clr (i) := clr (upBound)
        dVal (i) := dVal (upBound)
        upBound := upBound - 1;
    end remove

    proc addSort (x : int, y : int, x2 : int, y2 : int, d : int, c : int)
        if upBoundSort = maxBoundSort then
            maxBoundSort := maxBoundSort + 1
            new xSortVal, maxBoundSort
            new ySortVal, maxBoundSort
            new xSortVal2, maxBoundSort
            new ySortVal2, maxBoundSort
            new clrSort, maxBoundSort
            new dSortVal, maxBoundSort
        end if
        upBoundSort := upBoundSort + 1
        xSortVal (upBoundSort) := x
        ySortVal (upBoundSort) := y
        xSortVal2 (upBoundSort) := x2
        ySortVal2 (upBoundSort) := y2
        clrSort (upBoundSort) := c
        dSortVal (upBoundSort) := d
    end addSort

    proc update
        loop
            var iNum : int := -1
            var iNumValue : int := 0
            for i : 0 .. upBound
                if dVal (i) > iNumValue then
                    iNum := i
                    iNumValue := dVal (i)
                end if
            end for
            addSort (xVal (iNum), yVal (iNum), xVal2 (iNum), yVal2 (iNum), dVal (iNum), clr (iNum))
            remove (iNum)
            exit when upBound = -1
        end loop
    end update

    proc draw
        for i : 0 .. upBoundSort
            drawfillbox (xSortVal (i), ySortVal (i), xSortVal2 (i), ySortVal2 (i), clrSort (i))
        end for
        upBoundSort := -1
    end draw

end buff

var point1 : pointer to buff
new buff, point1
point1 -> add (50, 50, maxx - 50, maxy - 50, 10, black)
point1 -> add (100, 100, maxx - 100, maxy - 100, 3, red)
point1 -> add (75, 75, maxx - 75, maxy - 75, 5, green)
point1 -> add (175, 175, maxx - 175, maxy - 175, 1, blue)
point1 -> update
point1 -> draw
Author:  Lucas [ Tue Mar 22, 2011 7:55 pm ]
Post subject:  RE:Help with 3D
Demon wasp - lol sry, my bad :/
copthesaint - well once i read the turorial on classes and learn what buffers are, im sure itl be very useful Smile thatl maybe take a day or two
Author:  Raknarg [ Wed Mar 23, 2011 10:28 am ]
Post subject:  RE:Help with 3D
whoops, missed the question. -.-'

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