[bb] positionsprite() by D4NM4N [ 1+ years ago ]

[BlitzBot]

Title : positionsprite()
Author : D4NM4N
Posted : 1+ years ago

Description : This may be of use to someone,

its a simple utility to convert 2d coords back in to a virtual 2d screen for using sprites or other flat entities.
to test it, use a sprite with a cross in the center to see exactly where plotted.

I have seen several other ways of doing this, and although brilliant, are hard to trace through, so ive done this to keep uneccasary maths to a minimum and make it easy to follow.

the sprites are approx 3bu in front of the camera, so people who use insanely small scales may want to set entityorder to -1 for the sprites.

;possible uses:
;    HUD
;   lens flares
;   displaying 'lives' etc

Code :

Code (blitzbasic) Select Expand

;--------------------------------------------------------------------------------
;A couple of functions to display 3d sprites using 2d coordinates!!
;By dan@d-grafix  
;--------------------------------------------------------------------------------
;firstly ive kept it as simple as possible.
;im not going in to the calculations involved to work out the cam dist and scale factors, but this is a
;simple utility to convert 2d coords back in to a virtual 2d screen for using sprites or other flat entities.

;Positionsprite() - a simple Virtual 2d screen of 640x480 coordinate system for sprites. (works in any screen mode with these numbers)
;useprojectedx/y#() - a routne to convert position returned from projectedx/y() for higher screen resolutions

;use:
; positionsprite (entity, x(as 2d), y(as 2d), scale(1 keeps original size (256x256) for actual screen coords))
; useprojectedx/y# (coords# (coordinate for conversion))

;possible uses:
; HUD
; lens flares
; displaying 'lives' etc

;rules:
; sprites must be parented to the primary camera (with normal zoom?(not tested for this))
; screen modes must be equally proporsonate to 640x480... ie 320x240 1024x768 etc otherwise the you may loose some Y!
; its not 100% accurate and (may) produce funny results when tiled sprite are used although this may be fixable with some fiddling
; the scale factor of 1.0   is calculated from sprites loaded at 256x256. for smaller ones adjust it as appropriate







;--------------------------------------------------------------------------------
;gfx setup
;--------------------------------------------------------------------------------
;try it with various screen modes
Graphics3D 1024,768,16,1

Global gwidth :gwidth  =GraphicsWidth()
Global gheight :gheight =GraphicsHeight()


cam=CreateCamera()
sprite1=LoadSprite("    your sprite.png      ",1,cam)
sprite2=CopyEntity(sprite1,cam)
sprite3=CopyEntity(sprite1,cam)



;--------------------------------------------------------------------------------
;demo code
;--------------------------------------------------------------------------------
scale#=1

;position some sprites using virtual 640x480 coords (works in all relative screen modes)
positionsprite (sprite1,0,0,scale) ;prints in top corner
positionsprite (sprite2,639,479,scale) ; prints in bottom corner (-1 to show gren cross)

;position sprite using true screen coords (useful for use with projectedx/y() in different res modes ie. for lens flares)
px#=useprojectedx#(512)
py#=useprojectedy#(384)
positionsprite (sprite3,px#,py#,scale) ; prints at actual screen coords for grafx mode!

RenderWorld()

;draw some 2d text guides to see whats happening
Text 50,10,"Virtual coord = 0,0"
Text gwidth-200,gheight-20,"Virtual coord = 640,480"
Text 512,384,"real screen coord = 512,384";

Flip

        waitkey()


;--------------------------------------------------------------------------------
;projection coord converters
;--------------------------------------------------------------------------------
Function useprojectedx#(coord#)
div#=640/Float(gwidth)
Return coord*div
End Function

Function useprojectedy#(coord#)
div#=480/Float(gheight)
Return coord*div
End Function

;--------------------------------------------------------------------------------
;Position sprite on ' virtual 2d '  3d screen
;--------------------------------------------------------------------------------
Function positionsprite(sprite,x#,y#,sps#=1.0,zdi#=3.2);zdi is precalculated and should not be changed (5.1 for upgrade to 1024)
sps = sps*1.28 ; 1.29 is precalculated too (best leave)
cx#=(x-(640*.5))*.01
cy#=(y-(480*.5))*.01
ScaleSprite sprite,sps,sps
PositionEntity sprite,cx,-cy,zdi
End Function

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