How to find the isometric tile under the mouse?

BlitzMax Forums/BlitzMax Beginners Area/How to find the isometric tile under the mouse?

Bremer

(Posted 2010) [#1]

If you look at this picture:

In this example it is a 5x5 grid stored in an array.

How would you find out which tile that the user is clicking on?

Difference

(Posted 2010) [#2]

First thing that springs to my mind is:

Make two axis vectors with origin in the middle lowest corner.
Find the points (pointA , pointB) closest to mousexy on both vectors.
Get the distance between the origin and pointA and quantize it to get tilex.
Get the distance between the origin and pointB and quantize it to get tiley.

xlsior

(Posted 2010) [#3]

nice picture by the way -- are those graphics from the project you're actually working on?

Czar Flavius

(Posted 2010) [#4]

Oh God this brings back terrible, terrible nightmares.

Bremer

(Posted 2010) [#5]

are those graphics from the project you're actually working on?

No it was just something random I found using google.

Oh God this brings back terrible, terrible nightmares.

Why, is it overly complex?

Czar Flavius

(Posted 2010) [#6]

Let's say each tile is 64x32. Create a 64x32 sprite which is just a blank, flat square ie no depth or height to the tile. The rest is transparent colour. Now have a 1x1 pixel image. Do a collision check between the 1x1 image on your mouse pointer and each tile's position using the flat (invisible) testing sprite.

Bremer

(Posted 2010) [#7]

I have been spending some time looking around on the web again today, and I came across this article, which I am not sure why, I did not find yesterday:

http://www.gamedev.net/reference/articles/article747.asp

Using these tiles and a color map tile I managed to come up with something that looks to be working.

SuperStrict

Graphics 1024,768

SeedRnd(MilliSecs())

Global tile1:TImage = LoadImage("tile_grass.png",0)
Global tile2:TImage = LoadImage("tile_water.png",0)
Global tile3:TImage = LoadImage("tile_dirt.png",0)

Global mousemapiso:TImage = LoadImage("MouseMapIso.png",0)

Global map:Int[12,45]
For Local y:Int = 0 To 44
For Local x:Int = 0 To 11
	map[x,y] = Rnd(3)
Next
Next

Global tileselectx:Int = 0
Global tileselecty:Int = 0

While Not KeyHit(KEY_ESCAPE)
	Cls
	drawmap()
	Flip

	If MouseHit(1) Then
		Local regionX:Int = (MouseX() / 64)
		Local regionY:Int = (MouseY() / 32) * 2
		Local mapX:Int = MouseX() Mod 64
		Local mapY:Int = MouseY() Mod 32
		Local rgb:Int = ReadPixel(LockImage(mousemapiso),mapX,mapY)
		Select rgb
			Case -65536
				tileselectx = regionX - 1
				tileselecty = regionY - 1
			Case -256
				tileselectx = regionX
				tileselecty = regionY - 1
			Case -1
				tileselectx = regionX
				tileselecty = regionY
			Case -16711936
				tileselectx = regionX - 1
				tileselecty = regionY + 1
			Case -16776961
				tileselectx = regionX
				tileselecty = regionY + 1
		End Select
	End If
Wend
End

Function drawmap()
	Local i:Int = 0
	For Local y:Int = 0 To 44
	For Local x:Int = 0 To 11
		If tileselectx = x And tileselecty = y Then
			SetColor 255,255,255
			Else
			SetColor 128,128,128
		End If
		Local tx:Int = x*64
		Local ty:Int = y*16
		If i = 1 Then tx :+ 32
		Select map[x,y]
			Case 0
				DrawImage(tile1,tx,ty)
			Case 1
				DrawImage(tile2,tx,ty)
			Case 2
				DrawImage(tile3,tx,ty)
		End Select
	Next
	i = 1-i
	Next
End Function

This is not code from the game, just something I quickly made to test out the suggestion from that article.

I hope someone else find it useful as well.

Enyaw

(Posted 2010) [#8]

I wrote a bit of code that works out the mouse position on a isometric grid - http://www.blitzbasic.com/codearcs/codearcs.php?code=2608 that you might find usefull and easy to work out how it works.

Raph	(Posted 2010) [#9]

I do what Czar Flavius said. More, if you do it when you go to draw, you can also do things like highlight the hovered tile, etc.