Cannot Generate 3D spherical Model.

copthesaint · **Posted:** Sat Mar 24, 2012 6:18 pm

I have been spending the last week trying to figure out how to generate 3D Spheres for my remake of my asteroids game Ive been working on. However I am having trouble with the faces. What this class does is first get the amount of vertices for the sphere then it sets the values of x, y, and z for the vertices, then with that information it creates faces "triangles" for the points. The generator has to be dynamic so that when The Quality increases or decreases, then the amount of faces change for the sphere.
I've spent alot of time trying to get just one side of the sphere to appear however I have been getting poor results every way Ive been trying to do this. This is my third time remaking this class. In the .exe Ive added, Ive changed a few of the values from below. The quality is set to 8 just so more points are created so I can show more faces, and set (quality - 2) *for creating points* to 5 just so you can see how it shows the triangles further down.

I really need some help, I defiantly need another opinion.

Turing:

class AsteroidGenerator
import Model3D
export InitializeAsteroid, ExportAsteroid
var boundSet : flexible array 0 .. -1 of int
var points : flexible array 0 .. -1 of array 0 .. 2 of real
var faces : flexible array 0 .. -1 of array 0 .. 2 of int
var facesBound, pointsBound, boundSize : int := -1
var quality : int := 4

function GetPoint (i : int, j : int) : int
var tempNum : int := 0
for y : 0 .. i - 1
tempNum := tempNum + (boundSet (y))
end for
tempNum := tempNum + j
result tempNum
end GetPoint

procedure AddFace (x, y, z : int)
facesBound := facesBound + 1
if facesBound > upper (faces) then
new faces, facesBound
end if
faces (facesBound) (0) := x
faces (facesBound) (1) := y
faces (facesBound) (2) := z
end AddFace

procedure AddFaces (p : array 0 .. 4 of int)
for i : 1 .. 3
AddFace (p (0), p (i), p (i + 1))
end for
end AddFaces

procedure InitializeAsteroid (q : int, width, height, depth : real)
boundSize := (quality * 2) - 1
if boundSize > upper (boundSet) then
new boundSet, boundSize
end if
var pointsSet : int := 1
boundSet (0) := 1
for i : 1 .. quality
pointsSet := boundSet (0)
for j : 1 .. i - 1
pointsSet := pointsSet + boundSet (j)
end for

boundSet (i) := pointsSet + 2
end for

for i : 0 .. (quality - 1)
boundSet (boundSize - i) := boundSet (i)
end for

for i : 0 .. boundSize
var DepthPoints : real := cosd (180 / boundSize) * i
var AngleInc : real := (360 / boundSet (i))
put boundSet (i)
for j : 0 .. boundSet (i) - 1
pointsBound := pointsBound + 1
if pointsBound > upper (points) then
new points, pointsBound
end if
points (pointsBound) (0) := (width * DepthPoints) * cosd (AngleInc * j) * 0.01
points (pointsBound) (1) := (height * DepthPoints) * sind (AngleInc * j) * 0.01
points (pointsBound) (2) := (depth * DepthPoints) * 0.01

end for
end for

for i : 0 .. quality - 2
for j : 0 .. boundSet (i) - 1
var p : array 0 .. 4 of int
p (0) := GetPoint (i, j)
p (1) := GetPoint (i + 1, j * 2 - 1)
p (2) := GetPoint (i + 1, j * 2 + 0)
p (3) := GetPoint (i + 1, j * 2 + 1)
p (4) := GetPoint (i, j + 1)
if j = 0 then
p (1) := GetPoint (i + 1, boundSet (i + 1)) - 1
end if
if j = boundSet (i) then
p (4) := GetPoint (i, 0)
end if
AddFaces (p)
end for
end for

for i : 0 .. facesBound
put "Face #", i, " {", faces (i) (0), ",", faces (i) (1), ",", faces (i) (2), "} " ..
View.Update
%delay (500)
end for
put ""
put "NumFaces: ", facesBound, " NumPoints: ", pointsBound
View.Update
delay (1000)
end InitializeAsteroid

function ExportAsteroid : pointer to Model3D
var Asteroid3D : ^Model3D
new Model3D, Asteroid3D

Asteroid3D -> SetConstants (pointsBound + 1, facesBound + 1)
var exportPoints : array 1 .. (pointsBound + 1) of array 1 .. 3 of real
for i : 1 .. (pointsBound + 1)
for j : 1 .. 3
exportPoints (i) (j) := points (i - 1) (j - 1)
end for
end for
Asteroid3D -> AddPoints (exportPoints)
var exportFaces : array 1 .. (facesBound + 1) of array 1 .. 3 of int
for i : 1 .. (facesBound + 1)
for j : 1 .. 3
exportFaces (i) (j) := faces (i - 1) (j - 1)
end for
end for
Asteroid3D -> AddFaces (exportFaces)

result Asteroid3D
end ExportAsteroid

end AsteroidGenerator

Zren · **Posted:** Sat Mar 24, 2012 7:58 pm

The keyword you're looking for is 'mesh'.

And you can't really say "only use this many vertices". You might run into situations where there aren't enough, or too many.

The smallest 3D shape is a tetrahedron (4 sided dice). Sphere's seem to start with a 8 sided diamond made of triangles for better symmetry though. That's probably since all the starting points are on the axes.

Imagine breaking up each of it's triangles into 3 (1 new vertice in the middle) or 4 (triforce) smaller triangles. For a sphere, each point would be pushed sphereRadius away from the origin of the sphere.

http://sol.gfxile.net/sphere/index.html

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

From there, you could just randomize everything like:

* radius
* skip a triangles to break up (make sure you don't skip many at the higher depths)
* shift the angle to the point from sphere origin a bit.

copthesaint · **Posted:** Sat Mar 24, 2012 9:43 pm

Ahh, I understand Thank you zren hadnt thought of it that way. I will try thanks.

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