Using the Projection Matrix to zoom in on a screen

Hmmm...A quick hack (didn't bother sorting out the origin) and it appears to be working alright here...

Strict

Type TVirtualGraphics
	Global virtualWidth, virtualHeight
	Global xRatio!, yRatio!
	
	Function Set(width=640, height=480, scale#=1)
		TVirtualGraphics.virtualWidth = width
		TVirtualGraphics.virtualHeight = height
		TVirtualGraphics.xRatio! = width / Double(GraphicsWidth())
		TVirtualGraphics.yRatio! = height / Double(GraphicsHeight())
		
	?Win32
		Local D3D7Driver:TD3D7Max2DDriver = TD3D7Max2DDriver(_max2dDriver)
			
		If D3D7Driver
			Local matrix#[] = [2.0 / (width / scale#), 0.0, 0.0, 0.0,..
			 										0.0, -2.0 / (height / scale#), 0.0, 0.0,..
			 										0.0, 0.0, 1.0, 0.0,..
		 											-1 - (1.0 / width), 1 + (1.0 / height), 1.0, 1.0] ',scale#]
			
			D3D7Driver.device.SetTransform(D3DTS_PROJECTION, matrix)
		Else
	? 
		glMatrixMode(GL_PROJECTION)
		glLoadIdentity()
		glortho(0, width / scale#, height / scale#, 0, -1, 1)
		glMatrixMode(GL_MODELVIEW)
		glLoadIdentity()
	?Win32
		EndIf
	?
	End Function
	
	Function MouseX()
		Return (BRL.PolledInput.MouseX() * TVirtualGraphics.xRatio!)
	End Function
	
	Function MouseY()
		Return (BRL.PolledInput.MouseY() * TVirtualGraphics.yRatio!)
	End Function
End Type

'----------------------------------------------- TEST -----------------------------------------------

'SetGraphicsDriver GLMax2DDriver()
SeedRnd MilliSecs()

Local index = Rand(0, CountGraphicsModes() - 1)
Local screenW, screenH, screenD, screenR

GetGraphicsMode(index, screenW, screenH, screenD, screenR) 

Graphics screenW, screenH, screenD
TVirtualGraphics.Set(1024, 768, 0.5)

HideMouse
AutoMidHandle True

Local image:TImage = LoadImage(getenv_("BMXPATH") + "/docs/src/bmax120.png")
Assert image Else "Oi...What's happend to yer docs?"

Local x = Rand(0, TVirtualGraphics.virtualWidth - 1)
Local y = Rand(0, TVirtualGraphics.virtualheight - 1) 
Local xInc = Rand(1, 4)
Local yInc = Rand(1, 4)
Local scale#

SetClsColor 0, 0, 100

Repeat
	x :+ xInc
	If x >= TVirtualGraphics.virtualWidth
		x = TVirtualGraphics.virtualWidth - 1
		xInc = -xInc 
	ElseIf x < 0
		x = 0
		xInc = -xInc
	EndIf
	
	y :+ yInc
	If y >= TVirtualGraphics.virtualHeight
		y = TVirtualGraphics.virtualHeight - 1
		yInc = -yInc 
	ElseIf y < 0
		y = 0
		yInc = -yInc
	EndIf
	
	scale# = 1 + (Cos(MilliSecs() / 10.0) * 0.5)
	
	Cls
	SetTransform(Sin(MilliSecs() / 40.0) * 180.0, scale#, scale#)
	DrawImage image, x, y
	
	SetTransform(0, TVirtualGraphics.xRatio!, TVirtualGraphics.xRatio!) 
	DrawText screenW + " x " + screenH + " x " + screenD, 12, 12
	
	Plot TVirtualGraphics.MouseX(), TVirtualGraphics.MouseY()

	Flip
Until KeyHit(KEY_ESCAPE)

End

...as expected, it seems to work fine with the extra LoadIdentity() too?

??

[edit]
Aha...The GL section of code I've previously posted differs from the code I have here (0 rather than -1 for nearVal), not sure how that happened but fixed wherever I found it. :o/

I'll stop talking to myself now. ;o)
[edit]