Visibility for Hexes
Author
I'm having trouble digging up resources for determining which hexes touch/intersect the line between the center of two other given hexes. Been trying the problem by myself for most of the summer, and not a single stroke of genius has struck.
So, here I am to wave the lightning rod around. Any ideas? Links?
i am certain there are better ways, but i once did it like this:
treat your hex grid as if it were an image (likely just as they are on the screen)
create a vector pointing from the starting hex to the end hex.
check the angle of that vector and go to the next hex (if its between -30° and +30° go up, 30°-90° up/right etc)
start again from the new hex until you reach your destination
(don't have any code anymore, hope i got it right)
treat your hex grid as if it were an image (likely just as they are on the screen)
create a vector pointing from the starting hex to the end hex.
check the angle of that vector and go to the next hex (if its between -30° and +30° go up, 30°-90° up/right etc)
start again from the new hex until you reach your destination
(don't have any code anymore, hope i got it right)
Author
Hmm... that might actually work well enough. I'll give it a shot.
If anyone has any other ideas, please do post. A very searchable forum is a good forum.
If anyone has any other ideas, please do post. A very searchable forum is a good forum.
Author
Well, I've got a quick test working, hashed up in Visual Basic... but I've hit an odd problem. Very odd. It won't 'scan' sideways. I'm using flat-top hexes. When the line between two hexes is between up-right and down-right, or between up-left and down-left, the scanner just won't move in that direction. I'd post a screenshot if I had a server to put it on.
Here's my code so far...
The if blocks based on (aX mod 2) is for accounting for the staggered columns (odd columns are shifted down by a halfhex).
Did I do something fundamentally wrong?
Here's my code so far...
Public Sub visCast(sX As Integer, sY As Integer, eX As Integer, eY As Integer) Dim rtX As Double, rtY As Double, reX As Double, reY As Double Dim dX As Double, dY As Double, dL As Double Dim aX As Integer, aY As Integer Dim aTrace As Boolean ' Visibility Flag aTrace = True ' Location Tracker aX = sX aY = sY ' Destination hex true center reX = (eX * 1#) reY = (eY * 1#) + (0.5 * (eY Mod 2)) Do While aX <> eX And aY <> eY And ptInMap(aX, aY) ' Set visibility If MapData(aX, aY) Then Exit Sub ' aTrace = False VisData(aX, aY) = aTrace ' Current eval. hex true center rtX = (aX * 1#) rtY = (aY * 1#) + (0.5 * (aY Mod 2)) ' Get delta to next hex dX = reX - rtX dY = reY - rtY dL = 1 / Sqr(dX * dX + dY * dY) dX = dX * dL dY = dY * dL ' 0.86602540378444 = sin(PI/3) If dY <= -0.86602540378444 Then ' Straight Up aY = aY - 1 ElseIf dY >= 0.86602540378444 Then ' Straight Down aY = aY + 1 ElseIf dY <= 0 Then ' Upward If dX >= 0 Then ' Up-Right If (aX Mod 2) Then aX = aX + 1 Else aX = aX + 1 aY = aY - 1 End If Else ' Up-Left If (aX Mod 2) Then aX = aX - 1 Else aX = aX - 1 aY = aY - 1 End If End If ElseIf dY > 0 Then ' Downward If dX >= 0 Then ' Down-Right If (aX Mod 2) Then aX = aX + 1 aY = aY + 1 Else aX = aX + 1 End If Else ' Down-Left If (aX Mod 2) Then aX = aX - 1 aY = aY + 1 Else aX = aX - 1 End If End If End If Loop If MapData(aX, aY) Then Exit Sub ' aTrace = False VisData(aX, aY) = aTrace End SubThe if blocks based on (aX mod 2) is for accounting for the staggered columns (odd columns are shifted down by a halfhex).
Did I do something fundamentally wrong?
Author
Answer; yup. Cor, am I an idiot...
This line here was my problem.
When we have aY == eY, then we have (False And True And True), and we quit.
So. Got a decent algorithm here, although it's still subject to some odd spots that should be visible, and some odd spots that shouldn't (mostly involving the fact I always blindly step to the 'middle' of hexes; I could add some fudging to get cleaner results).
Thanks for the help!
This line here was my problem.
' The old nonfunctional: Do While aX <> eX And aY <> eY And ptInMap(aX, aY)' What it should've been: Do While (aX <> eX Or aY <> eY) And ptInMap(aX, aY)When we have aY == eY, then we have (False And True And True), and we quit.
So. Got a decent algorithm here, although it's still subject to some odd spots that should be visible, and some odd spots that shouldn't (mostly involving the fact I always blindly step to the 'middle' of hexes; I could add some fudging to get cleaner results).
Thanks for the help!
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