2D Alpha with 3D Functions

Hello,

I have a Fullscreen 1024x768 Background and want to let some 2D Clouds fly over with Alpha-Blending.

Because of the big images (The Clouds-Image is fullscreen, too) the ReadPixelFast and WritePixelFast are too slow for Real-Time.

To get to the point: Someone mentioned in another thread, that it would be possible to make 2D-Alpha-Blending with Blitz3Ds Alpha Functions. But how??

I tried but my 2D graphics does not change when i use Blitz3Ds functions to change light or make alpha blending.

Do I have to use DrawSprite instead of DrawImage? Wouldn't it be slower with that? Or do I have to create a plane and put my 2D graphics as Texture on it?

Plz Help!


Greetings
GrrBrr

Look for Syntax's "Sprite Control" its on BlitzCoder showcase someplace.

ok, i'll take a look, thanks

Hey, thanks coffee. Did that MaskImage3D function help?

GrBrr,
If you want to try out SpriteControl for your alpha'd clouds do something like this:

; the include file
Include "Sprite Control.bb"

Const sw=640,sh=480 ; display dimensions

; set up the 3d display
Graphics3D sw,sh
SetBuffer BackBuffer()

; create a main camera
cam=CreateCamera()
CameraClsMode cam,False,True ; < do not clear color buffer

; create a sprite pivot and attach to camera
spritecam=CreateSpritePivot(cam)

; load images/sprites
bkg=LoadImage("background.jpg")
cloud=LoadImage3D("cloud.jpg")
EntityAlpha cloud,0.3 ; fade out the cloud

x#=sw*0.9 : y=sh*0.5

Repeat
	x=x-0.7
	TileBlock bkg
	DrawImage3D cloud,x,y
	RenderWorld
	Flip
Until KeyHit(1)
End

If you are using a full-screen sized image for the clouds (i.e 1024x1024) and experience slowdown (due to fillrate problems) you have a few options:

* Change the size of your clouds image to say, 512x512 and use

cloud=LoadImage3D("cloud.jpg")
ResizeImage3D cloud,1024,1024

* Cut your image up and create individual clouds. Then ..

Dim cloud(10)
For c=1 to 10
cloud(c)=LoadImage3D("cloud"+Str$(c)+".jpg")
Next

This second method at least allows you to move your clouds at different speeds.

Oh, and if you want nice and sharp clouds use ClearTextureFilters before loading the sprites.

thanks for the help
it works now :))))