This is brilliant! Why didn't I think of this?
I don't think the effect is obvious so I changed the presentation:
(You will need Silverman's included image to run this code)
set display mode 800,600,32
sync on
sync rate 60
rem DBC v120
rem alpha blending example
`make random alpha texture, and create memblock(alpha)
alpha=2
for x=0 to 294 step 30
for y=0 to 240 step 30
color=rnd(255)
ink rgb(color,color,color),0
x1=x
y1=y
x2=294-x
y2=240-y
box x1,y1,x2,y2
next y
next x
get image alpha,0,0,294,240
sync
make memblock from image alpha,alpha
`load texture, and create memblock(texture)
texture=1
load image "294px-Morrice-La_veille_maison_Holton_a_Montreal.jpg",texture
make memblock from image texture,texture
backdrop on
texture backdrop texture
`if size memblock texture are different, then stop
size=get memblock size(texture)
if get memblock size(alpha)<>size then end
`mix 'alpha' and 'texture' ; copy result in memblock 'texture'
for pos=12 to size-1
valu=((memblock byte(texture,pos)+1)*(255-memblock byte(alpha,pos)))/255.0
write memblock byte texture,pos,valu
next pos
`make mixed texture
delete image texture
make image from memblock texture,texture
`free memory
delete memblock texture
delete memblock alpha
`make object for mixed texture
make object plain texture,294,240
texture object texture,texture
level=128
set object ambient texture,rgb(level,level,level)
set object diffuse texture,rgb(level,level,level)
position object texture,0,60,0
ghost object on texture
`make object for alpha texture
make object plain alpha,294,240
texture object alpha,alpha
set object ambient alpha,rgb(255,255,255)
set object diffuse alpha,rgb(255,255,255)
position object alpha,0,60,0
ghost object on alpha,1
`green object
`make object box 5,1024,128,8
`color object 5,rgb(0,128,0)
`position object 5,0,0,300
`position camera
autocam off
position camera 0,120,-300
`main
repeat
xrotate object texture,wrapvalue(object angle x(texture)+0.5)
xrotate object alpha,wrapvalue(object angle x(alpha)+0.5)
` xrotate object 5,wrapvalue(object angle x(5)+1.0)
sync
until scancode()
delete image texture
delete image alpha
sync
end
Edit:
I changed the images for the blending example to show what it could be used for. Attached -->
WARNING: The above comment may contain sarcasm.
