# Thread: [RESOLVED] how can i walk throw the line?

1. ## [RESOLVED] how can i walk throw the line?

see these image:
https://2.bp.blogspot.com/-STOKeDBaa...0/distanc1.png

i know calculate the AB distance using the Pythagorean theorem.
my question is: imagine that i'm on vector A, how can i move, vector a vector, to B?
is just:
X = X + 1
Y = Y + 1
?
and, true, depends on direction.. what i don't know use it..
can anyone explain these to me?
and yes these is a 2D, i need to know, too, in 3D.  Reply With Quote

2. ## Re: how can i walk throw the line?

vector by vector AB= AO + OB :

AO |X=xb-xa + OB|X=0.........= AB |X =xb-xa
.....|Y=0.............|Y=yb-ya..........|Y =yb-ya

the coordinates of a vector are the coordinates of the last point minus the first point

Euclidian vector  Reply With Quote

3. ## Re: how can i walk throw the line?

You wouldn't add 1 to each, unless you want to move at a 45 degree angle.
You need the ratio of the change in values. Traditionally, I think, the ratio is given as dY/dX.

Depending on what is desired, I don't calculate the ratio, but just calculate the delta, and then scale each delta based on a step size, or a percentage.

In a card game I wrote, for instance, I want cards to return "home" when they are free to do so, and I want to be able to move several cards at the same time so you can have multiple cards moving across the form on a line from where they were to the home positions.

Since the cards should "stack" in the home position in order, from Ace to King, I don't want a lower card to arrive after a higher card. If I simply moved the cards at the same speed, the closer cards would arrive earlier than cards further away, regardless of what value the card was.

So, I move the cards the same number of steps to reach home. If the card is further away, its steps will be larger. So, when I start moving the cards in order, from low to high, the lower card will arrive before the higher card regardless of which card is closer to home at the start.

Using your diagram,
Code:
```dx = Xb - Xa
dy = Yb - Ya

To move from point A to point B in 50 steps.
stepX = dx / 50
stepY = dy / 50

PosX = Xa
PosY = Ya

For I = 1 to 49
PosX = PosX + stepX
PosY = PosY + stepY
draw new position indication
Next
PosX = Xb  'just to ensure we end up exactly on the point, no rounding issues
PosY = Yb
draw at final position.```
Or you could use a percentage position to place at a specific position.
'calculate a point 75% of the way from A to B
PosX = Xa + .75 * dx
PosY = Ya + .75 * dy

There are other alternatives, but the above should be fairly understandable, I hope.

For 3D, just add the same code for the Z axis values, i.e. calculate dz and scale it by the same amount as you scale x and Y to get a new 3d point along a straight line between the two points.  Reply With Quote

4. ## Re: how can i walk throw the line?

isn't 100% but works fine:
Code:
```'if the vector is the destiny position, change the parameter order for get the right result... i had tested
Private Function GetInCamVector(Origin As Position3D, Destiny As Position3D) As Position3D
Dim Steps As Double
Steps = Math.Sqr(Math.Abs(Destiny.x - Origin.x) ^ 2 + Math.Abs(Destiny.Y - Origin.Y) ^ 2 + Math.Abs(Destiny.Z - Origin.Z) ^ 2)
Steps = Ceiling(Steps)

Dim increment As Position3D
increment.x = (Destiny.x - Origin.x) / Steps
increment.Y = (Destiny.Y - Origin.Y) / Steps
increment.Z = (Destiny.Z - Origin.Z) / Steps

Dim nextpoint As Position3D
nextpoint = Origin
Dim i As Integer

Dim inter As Position3D
Dim size As Size3D
For i = 1 To Steps
nextpoint.x = nextpoint.x + increment.x
nextpoint.Y = nextpoint.Y + increment.Y
nextpoint.Z = nextpoint.Z + increment.Z
inter.x = Math.Round(nextpoint.x)
inter.Y = Math.Round(nextpoint.Y)
inter.Z = Math.Round(nextpoint.Z)
If (IsOnCamera(inter, camera1.Position, camera1.size) = True) Then
GetInCamVector = inter
Exit For 'yes i must exit the 'for' for not get unexpected results
End If
Next i
End Function```
thank you so much for all  Reply With Quote

5. ## Re: how can i walk throw the line?

i'm testing more these function, but i don't get some points and i don't know why Code:
```'if the line don't use Z, the Z value must be zero
Public Function GetLinePoints(ByRef Origin As Position3D, ByRef Destiny As Position3D) As Position3D()
Dim Steps As Double
Dim Points() As Position3D

Steps = Math.Sqr(Math.Abs(Destiny.X - Origin.X) ^ 2 + Math.Abs(Destiny.Y - Origin.Y) ^ 2 + Math.Abs(Destiny.Z - Origin.Z) ^ 2)
Steps = Ceil(Steps)

Dim increment As Position3D
If (Steps = 0) Then Steps = 1
increment.X = (Destiny.X - Origin.X) / Steps
increment.Y = (Destiny.Y - Origin.Y) / Steps
increment.Z = (Destiny.Z - Origin.Z) / Steps

Dim nextpoint As Position3D
nextpoint = Origin
Dim i As Integer

Dim inter As Position3D
Dim size As Size3D
ReDim Points(Steps)
For i = 1 To Steps
nextpoint.X = nextpoint.X + increment.X
nextpoint.Y = nextpoint.Y + increment.Y
nextpoint.Z = nextpoint.Z + increment.Z
inter.X = Math.Round(nextpoint.X)
inter.Y = Math.Round(nextpoint.Y)
inter.Z = Math.Round(nextpoint.Z)
Points(i).X = inter.X
Points(i).Y = inter.Y
Points(i).Z = inter.Z
'Debug.Print "X: " + CStr(inter.X) + vbTab + "Y: " + CStr(inter.Y) + vbTab + "Z: " + CStr(inter.Z)
Next i
GetLinePoints = Points
End Function```
heres how i use it:
Code:
```Friend Sub DrawImageRectanglePoints(DestinationHDC As Long, Points() As Position3D, WorldSize As Size3D)
'Points(0) is the Upper-Left
'Points(1) is the Upper-Right
'Points(2) is the Low-Right
'Points(3) is the Low-Left

Dim PointsUpperDownLeft() As Position3D
PointsUpperDownLeft = GetLinePoints(Points(0), Points(3))
Dim PointsUpperDownRight() As Position3D
PointsUpperDownRight = GetLinePoints(Points(1), Points(2))
Dim X As Long
Dim Y As Long
Dim R As Long
Dim G As Long
Dim B As Long

Dim DrawPixelPoints() As Position3D
For Y = UBound(PointsUpperDownLeft) To 0 Step -1
DrawPixelPoints = GetLinePoints(PointsUpperDownLeft(Y), PointsUpperDownRight(Y))
For X = 0 To UBound(DrawPixelPoints)
Dim Point As POINTAPI
Dim color As Long
Dim PosX As Long
Dim PosY As Long
PosX = X
PosY = Y
If (PosX > ImageWidth) Then
While (PosX >= ImageWidth)
PosX = PosX - ImageWidth
Wend
End If

If (PosY >= ImageHeight) Then
While (PosY > ImageHeight)
PosY = PosY - ImageHeight
Wend
End If

GdipBitmapGetPixel hBitmap, PosX, PosY, color
R = color And &HFF
G = (color And &HFF00&) \ &H100&
B = (color And &HFF0000) \ &H10000
If (color = CLR_INVALID) Then Exit For
Point = ConvertPositon3DTo2D(DrawPixelPoints(X), WorldSize)
SetPixelV DestinationHDC, Point.X, Point.Y, RGB(R, G, B)
Next X
Next Y
End Sub```
the result is:
Attachment 179362
the bottom horizontal lines, aren't painted... maybe these function don't calculate that points on vertical line.... what i'm doing wrong?  Reply With Quote

6. ## Re: how can i walk throw the line?

- for get the line points is from up to bottom
- for draw the image is bottom to up  Reply With Quote

7. ## Re: how can i walk throw the line?

i found why i get that empty pixels... have to do with camera size... thank you so much for all  Reply With Quote

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