Post Processing

Blitz3D Forums/Blitz3D Programming/Post Processing

xtremegamr

(Posted 2010) [#1]

In some games (like Medal of Honor: Airborne) there are several post processing effects that add intensity (and eye candy) to the game. For example, in MOHA (and in many other games), the screen turns red as you take damage.

I've tried several different techniques to implement this effect in my games. My only problem is that all of these techniques KILL my frame rate; my FPS has never gone above 2FPS with post processing effects, even in fullscreen mode! Here's some code I cobbled together to demonstrate what I'm talking about.

Can anyone give me some pointers on how to speed this up? Or am I just going about this the wrong way?

;Post Processing
;Thrown together by xtremegamr to demonstrate post processing techinques
;Use the Arrow Keys to move around, and the SPACEBAR to toggle Post Processing effects

AppTitle "Post Processing"
Graphics 1024,768,0,2

;globals
Global FPS#
Global loopstart ;what was the MilliSecs() value when the loop started? (Used for FPS calculation)
Global looptime ;how long did the loop take (in millisecs)? (Used for FPS calculation)

;player type
Type player
	Field x,y
	Field spd
End Type

;load the player
Local p1.player=newplayer(GraphicsWidth()/2,GraphicsHeight()/2)

;post processing vars
Local postprocessing=False

;main loop
While Not KeyHit(1)
loopstart=MilliSecs()

SetBuffer BackBuffer()
ClsColor 255,255,255
Cls

;draw the player
drawplayer(p1)

;player controls
If KeyDown(200) Then p1\y=p1\y-p1\spd
If KeyDown(208) Then p1\y=p1\y+p1\spd
If KeyDown(203) Then p1\x=p1\x-p1\spd
If KeyDown(205) Then p1\x=p1\x+p1\spd
If KeyHit(57) Then postprocessing=Not postprocessing

;post processing?
If postprocessing Then pp()

;HUD
Color 0,0,0

If postprocessing Then
	Text 0,0,"Post Processing: On"
Else
	Text 0,0,"Post Processing: Off"
End If

Text 0,12,"FPS/Loop Time: " +FPS+ "/" +looptime+ "ms"

Text 0,24,"Press SPACEBAR to toggle post processing."
Text 0,46,"Use the Arrow Keys to move around."

Flip

looptime=MilliSecs()-loopstart
FPS=Float(1000)/looptime
Wend ;end of main loop
End

;draw()
;draws the player
Function drawplayer(p.player)

Color 255,0,0
Oval p\x,p\y,10,10,True

End Function

;newplayer()
;creates a new player and returns it's object handle
Function newplayer.player(x,y)

p.player=New player

p\x=x
p\y=y
p\spd=3

Return p

End Function

;pp()
;does post processing
Function pp()

;create a temporary buffer image
Local img=CreateImage(GraphicsWidth(),GraphicsHeight())

;blur screen
;     This works by running through each pixel in the buffer, and blending it with the color red.
LockBuffer ImageBuffer(img)
LockBuffer BackBuffer()
For x=1 To GraphicsWidth()
	For y=1 To GraphicsHeight()
		;get the pixel
		pix=ReadPixel(x,y,BackBuffer()) ;<-- for some reason, using ReadPixelFast here gives me a MAV. Any reason why?
		
		;blend this pixel's color with red (RGB=255,0,0)
		blendedcolor_r=(0.8*Red(pix))+(0.2*255)
		blendedcolor_g=(0.8*Green(pix))+(0.2*0)
		blendedcolor_b=(0.8*Blue(pix))+(0.2*0)
		
		;write this new blended color to the temporary buffer
		WritePixel(x,y, ARGB(blendedcolor_r,blendedcolor_g,blendedcolor_b,0), ImageBuffer(img))
	Next
Next
UnlockBuffer BackBuffer()
UnlockBuffer ImageBuffer(img)

;copy the buffer to the back buffer
CopyRect(0,0,GraphicsWidth(),GraphicsHeight(), 0,0, ImageBuffer(img), BackBuffer())

;get rid of the temp buffer
FreeImage img

End Function

;ARGB Seperator
;This isn't my code; I took it from the B3D code archives (http://www.blitzbasic.com/codearcs/codearcs.php?code=2537)
;This code seperates the RGB values from an integer
Function Alpha(ARGB)
Return (ARGB Shr 24) And 255
End Function 

Function Red(ARGB)
Return (ARGB Shr 16) And 255
End Function

Function Green(ARGB)
Return (ARGB Shr 8) And 255
End Function

Function Blue(ARGB)
Return ARGB And 255
End Function 

Function ARGB(Red,Green,Blue,Alpha)
Return ((Alpha And 255) Shl 24) Or  ((Red And 255) Shl 16) Or ((Green And 255) Shl 8) Or (Blue And 255)
End Function

puki	(Posted 2010) [#2]

Based on what you have shown, just use an alpha mesh as a filter.

Seeing as you are interested in this path:

How many games have you seen that exhibit retina retention - ie when the player looks into a bright light and gets the 'light blobs' retina retention?

I don't ever recall seeing it in any game - but it is easy to reproduce.

The concept for implementing this is tucked away in a Blitz3D demo - it's just most people probably overlooked it.

Ian Caio

(Posted 2010) [#3]

xtremegamr,

Those Post Processing effects are usually made using Pixel Shaders, and since Directx7 doesnt support shaders you cant make it exactly the same way with the same speed. But there are many ways to get cross that problem.

For example, that blood effect, you could put a sprite in front of the camera using pixel perfect math, paint it red, and maybe add a feel details with some texture, and then use entityalpha to make it fade away with the time.

If you use your imagination you can go far with this kind of effects :)

cya

xtremegamr

(Posted 2010) [#4]

Those Post Processing effects are usually made using Pixel Shaders, and since Directx7 doesnt support shaders you cant make it exactly the same way with the same speed.

I was afraid you'd say that. :)

For example, that blood effect, you could put a sprite in front of the camera using pixel perfect math, paint it red, and maybe add a feel details with some texture, and then use entityalpha to make it fade away with the time.

That sounds like a good idea. I think I'll try it.

Thanks to both of you guys, I appreciate the help.

Ross C

(Posted 2010) [#5]

or try the fast libs extention

Drak	(Posted 2010) [#6]

Using the sprite method doesn't work too bad. I have used it previously and think it looks alright. This is a link to the worklog and theres a link there to download the demo for that game if you'd like to see it.

http://www.blitzbasic.com/Community/posts.php?topic=88817

Here there's actually 3 splatters on the screen at different rates of fading:

Ross C

(Posted 2010) [#7]

Looks not bad actually :) I';lle xpand upon my comment i left last night about the fast libs. They will let you filter out everything, but red, green or blue, giving the whole screen, an only red, green or blue coloured appearance.

Matty

(Posted 2010) [#8]

Without fastlibs (which I've never used) you can also filter out all of a particular set of colours simply using a (for instance) red (255,0,0) quad / sprite multiply blended with the scene (use entity order and place it in front of the camera so that it renders last)

Ross C

(Posted 2010) [#9]

Ah, that's nice to know too :) Thanks!