[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

1. ;--------------------------------------------------------------------------------
2. ;A couple of functions to display 3d sprites using 2d coordinates!!
3. ;By dan@d-grafix  
4. ;--------------------------------------------------------------------------------
5. ;firstly ive kept it as simple as possible.
6. ;im not going in to the calculations involved to work out the cam dist and scale factors, but this is a
7. ;simple utility to convert 2d coords back in to a virtual 2d screen for using sprites or other flat entities.
8.  
9. ;Positionsprite() - a simple Virtual 2d screen of 640x480 coordinate system for sprites. (works in any screen mode with these numbers)
10. ;useprojectedx/y#() - a routne to convert position returned from projectedx/y() for higher screen resolutions
11.  
12. ;use:
13. ;       positionsprite (entity, x(as 2d), y(as 2d), scale(1 keeps original size (256x256) for actual screen coords))
14. ;       useprojectedx/y# (coords# (coordinate for conversion))
15.  
16. ;possible uses:
17. ;       HUD
18. ;       lens flares
19. ;       displaying 'lives' etc
20.  
21. ;rules:
22. ;       sprites must be parented to the primary camera (with normal zoom?(not tested for this))
23. ;       screen modes must be equally proporsonate to 640x480... ie 320x240 1024x768 etc otherwise the you may loose some Y!
24. ;       its not 100% accurate and (may) produce funny results when tiled sprite are used although this may be fixable with some fiddling
25. ;       the scale factor of 1.0   is calculated from sprites loaded at 256x256. for smaller ones adjust it as appropriate
26.  
27.  
28.  
29.  
30.  
31.  
32.  
33. ;--------------------------------------------------------------------------------
34. ;gfx setup
35. ;--------------------------------------------------------------------------------
36. ;try it with various screen modes
37. Graphics3D 1024,768,16,1
38.  
39. Global gwidth                   :gwidth  =GraphicsWidth()
40. Global gheight                  :gheight =GraphicsHeight()
41.  
42.  
43. cam=CreateCamera()
44. sprite1=LoadSprite("    your sprite.png      ",1,cam)
45. sprite2=CopyEntity(sprite1,cam)
46. sprite3=CopyEntity(sprite1,cam)
47.  
48.  
49.  
50. ;--------------------------------------------------------------------------------
51. ;demo code
52. ;--------------------------------------------------------------------------------
53.         scale#=1
54.        
55.         ;position some sprites using virtual 640x480 coords (works in all relative screen modes)
56.         positionsprite (sprite1,0,0,scale)              ;prints in top corner
57.         positionsprite (sprite2,639,479,scale)  ; prints in bottom corner (-1 to show gren cross)
58.        
59.         ;position sprite using true screen coords (useful for use with projectedx/y() in different res modes ie. for lens flares)
60.         px#=useprojectedx#(512)
61.         py#=useprojectedy#(384)
62.         positionsprite (sprite3,px#,py#,scale) ; prints at actual screen coords for grafx mode!
63.  
64.         RenderWorld()
65.  
66.         ;draw some 2d text guides to see whats happening
67.         Text 50,10,"Virtual coord = 0,0"
68.         Text gwidth-200,gheight-20,"Virtual coord = 640,480"
69.         Text 512,384,"real screen coord = 512,384";
70.        
71.         Flip
72.  
73.         waitkey()
74.  
75.  
76. ;--------------------------------------------------------------------------------
77. ;projection coord converters
78. ;--------------------------------------------------------------------------------
79. Function useprojectedx#(coord#)
80.         div#=640/Float(gwidth)
81.         Return coord*div
82. End Function
83.  
84. Function useprojectedy#(coord#)
85.         div#=480/Float(gheight)
86.         Return coord*div
87. End Function
88.  
89. ;--------------------------------------------------------------------------------
90. ;Position sprite on ' virtual 2d '  3d screen
91. ;--------------------------------------------------------------------------------
92. 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)
93.         sps = sps*1.28  ; 1.29 is precalculated too (best leave)
94.         cx#=(x-(640*.5))*.01
95.         cy#=(y-(480*.5))*.01
96.         ScaleSprite sprite,sps,sps
97.         PositionEntity sprite,cx,-cy,zdi
98. End Function

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