How I do create a function that returns two different values?

[Tamer via DotNetMonster.com]

I'm developing a graphic engine. I got all equations made, I need only to
understand how I can create a function that, once accepted three values (x;
y; z), it returns the two values (X; Y) coming from two distinct mathematical
processes. I don't want to use another global variable, I'm trying to be fast,
in order to use such a function even in this way:

Public Structure Point
x as double
y as double
z as double
End Structure

....
....

Dim PointA as Point, PointB as Point

With ...
.Line(Conv3D(PointA.x, PointA.y, PointA.z)) - (Conv3D(PointB.x,
PointB.y, PointB.z))
End With

....
....

And so on.
Thanks for reading, sorry for the gibberish English: I'm Italian.

[Ken Tucker [MVP]]

Hi,

Rod Stephens book Visual Basic Graphics Programing covers how to do
it. The book has sample apps that are written in vb6 but you can see how to
do the math.

Book
http://www.vb-helper.com/vbgp.htm

Tips on his web site about 3d graphics
http://www.vb-helper.com/index_graphics.html#3d

Ken
-----------------------
"Tamer via DotNetMonster.com" <fo***@DotNetMonster.com> wrote in message
news:53***********@DotNetMonster.com...
I'm developing a graphic engine. I got all equations made, I need only to
understand how I can create a function that, once accepted three values (x;
y; z), it returns the two values (X; Y) coming from two distinct
mathematical
processes. I don't want to use another global variable, I'm trying to be
fast,
in order to use such a function even in this way:

Public Structure Point
x as double
y as double
z as double
End Structure

....
....

Dim PointA as Point, PointB as Point

With ...
.Line(Conv3D(PointA.x, PointA.y, PointA.z)) - (Conv3D(PointB.x,
PointB.y, PointB.z))
End With

....
....

And so on.
Thanks for reading, sorry for the gibberish English: I'm Italian.

[Larry Lard]

Tamer via DotNetMonster.com wrote:

I'm developing a graphic engine. I got all equations made, I need only to
understand how I can create a function that, once accepted three values (x;
y; z), it returns the two values (X; Y) coming from two distinct mathematical
processes. I don't want to use another global variable, I'm trying to be fast,
in order to use such a function even in this way:

Public Structure Point
x as double
y as double
z as double
End Structure
The .NET Framework already includes a structure named Point (in
System.Drawing), so you should probably choose a different name for
your point structure, just to avoid any confusion. Maybe Point3D ? And
Point2D for your points on a plane? (Note that you probably shouldn't
use System.Drawing.Point for your 2D points, unless you are actually
using System.Drawing.Point itself).

Now, once you've got these two structures defined:

Public Structure Point3D
X As Double
Y As Double
Z As Double
End Structure
Public Structure Point2D
X As Double
Y As Double
End Structure

it's then just a matter of defining your conversion function such that
it accepts a Point3D and returns a Point2D. Depending on your
application, it may or may not make sense to make this conversion
function a member of Point3D. In this example I won't.

Public Function Conv3D(ByVal FromPoint As Point3D) As Point2D
Dim p As Point2D

'do the calculations
p.X = FromPoint.X
p.Y = FromPoint.Y + FromPoint.Z

Return p
End Function
Once you have done that, to do this kind of thing:

...
...

Dim PointA as Point, PointB as Point

With ...
.Line(Conv3D(PointA.x, PointA.y, PointA.z)) - (Conv3D(PointB.x,
PointB.y, PointB.z))
End With

...
...
You can say

Dim pt3A As Point3D, pt3B As Point3D

With ...
.Line(Conv3D(pt3A), Conv3D(pt3B))
End With

Where .Line is a procedure that takes two Point2D's as its arguments.

And so on.
Thanks for reading, sorry for the gibberish English: I'm Italian.

Better than my Italian :)

--
Larry Lard
Replies to group please

[Chris Dunaway]

Thanks for reading, sorry for the gibberish English: I'm Italian.

Better than my Italian :)

Better than some Americans' English!!

[Tamer via DotNetMonster.com]

Thank you very much, really! Well I come from some VB6 and QBasic programming
experience, so I completely missed the fact that I can declare a function as
a structure of my own... Thinking about it, now it makes me sense.

For the "point matter", well... I now that already exist a Point function.
I've using it for years for the conversion from 32bit colour information to
RGB (until yesterday, when I discovered GetRed, GetGreen and GetBlue function)
..
I'm actually using Point3D and Point2D structures (you're a mind-reader, uh?),
with xPt, yPt and zPt elements.

So, thanks a lot for your precious advice; as we say in Italy, I was getting
lost into a glass of water.
Tamer

Larry Lard wrote:

I'm developing a graphic engine. I got all equations made, I need only to
understand how I can create a function that, once accepted three values (x;

[quoted text clipped - 7 lines]

z as double
End Structure

The .NET Framework already includes a structure named Point (in
System.Drawing), so you should probably choose a different name for
your point structure, just to avoid any confusion. Maybe Point3D ? And
Point2D for your points on a plane? (Note that you probably shouldn't
use System.Drawing.Point for your 2D points, unless you are actually
using System.Drawing.Point itself).

Now, once you've got these two structures defined:

Public Structure Point3D
X As Double
Y As Double
Z As Double
End Structure

Public Structure Point2D
X As Double
Y As Double
End Structure

it's then just a matter of defining your conversion function such that
it accepts a Point3D and returns a Point2D. Depending on your
application, it may or may not make sense to make this conversion
function a member of Point3D. In this example I won't.

Public Function Conv3D(ByVal FromPoint As Point3D) As Point2D
Dim p As Point2D

'do the calculations
p.X = FromPoint.X
p.Y = FromPoint.Y + FromPoint.Z

Return p
End Function

Once you have done that, to do this kind of thing:

...
...

[quoted text clipped - 8 lines]

...
...

You can say

Dim pt3A As Point3D, pt3B As Point3D

With ...
.Line(Conv3D(pt3A), Conv3D(pt3B))
End With

Where .Line is a procedure that takes two Point2D's as its arguments.

And so on.
Thanks for reading, sorry for the gibberish English: I'm Italian.

Better than my Italian :)

--
Message posted via DotNetMonster.com
http://www.dotnetmonster.com/Uwe/For...b-net/200508/1