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Thanks for clearing that up.  I guess I had a different idea of how it work.  Logically for me the alpha would be a sliding scale with -1 being invisible through to 0 (the center) being 100% visible, and then onto 1 being double bright. 
Not sure if its a bug or my misunderstanding.  Here's my understanding of how alpha mode works in GLB

1) if the alphamode = 0 then it draws the sprite normally (no alpha blending at all and the sprite is 100% visible)
2) if the alphamode > 0 then the sprite is drawn with an additive blend i.e. it will be brighter than normal
3) if the alphamode < 0 then the sprite will be transparent i.e. -0.5 alpha mode means the sprite will be 50% transparent and -1.0 means 100% transparency (so its not visible)

Can some one confirm if this is correct?

OK, so if the above is correct then, an alpha mode of 0.5 means the sprite should be brighter.  However it is actually 50% transparent when used within a polyvector command.  Gernot is there something different we should consider when using alphamode and polyvectors? 




After a quick test the range seems to be when using polyvectors...

1 = sprite at 0% transparency (visible)

down to

0.001 = 100% transparency i.e. invisible sprite.

then back to 0% transparency when the alpha mode = 0.

This means to fade out a sprite I need to change the alphamode from 1 to 0.001 which is different from the manual says.
Yep its fixed now :)  Thanks very much for the quick update  :good:

It seems that when you use CreateScreen in landscape mode (480 x 320) the output isn't rotated.  Any chance this could be fixed?


Hi Quentin,

Nice demo, but that works fine if you only have one texture on your bitmap.  In your example you are creating a single texture 32 x 32.  Imagine your sprite had 2 images with a total size of 32 x 64... the first 32 x 32 (coord 0,0) being green grass, then second 32 x 32 (coords 64,0) being brown dirt.  Now the example you posted wouldn't work, because it would tile using both the green grass and the brown dirt.  If you supplied texture coordinates into the polyvector, it wouldn't repeat the pattern, but rather it would scale the texture to fit the mesh dimensions (which is good and we certainly like this functionality as it allows us to scale sprites easily). 

Just for some background info we are working on an iPhone framework and to keep speeds up we need to batch as much of the rendering as possible.  Therefore we use a single sprite sheet with multiple images.  Then we use polyvector to draw the images by supplying it the correct texture from the sprite sheet.  Being able to change the UV scale and UV positions using poly sprites should save some FPS, and allow us to make some pretty smart effects.

I've had a hunt around the forums and couldn't see anything related to this, but I was wondering if it was possible to be able to handle the UV parameters.  The idea being that you could make a nice single polyvectory and apply the texture multiple times to it.  Imagine I wanted to draw an area of grass, at the moment I would need to render say 30 tiles to cover the screen.  Wouldn't it be nice to render 1 polyvector and just change the UV parameter to repeat the texture 15 times on the x axis, and 15 times on the y axis.  Even better would then be the option to set the UV offsets.  This would then allow us to scroll the texture on polyvector. 

I can see a lot of practical uses for something this.


Doh!  Just worked out what I was doing wrong.  I was typing in the notes as described, but I hadn't actually saved the sourced coded before running the create help option.  ;/
Cheers Ocean thats handy to know :)  Do you have any more top tips like that?
Before you give up please can you test the file I just sent you.  Its a sprite test which I know runs on several machines.  I have sent the whole project file so that should resolve any filename issues.
Good question.  In Xcode you can compile using more than one SDK.  So I compiled the program using 2.2.1 SDK as well.  Did you check any of the suggestions I mentioned above?

AndyH just pointed out that GLB has its own help creator.  I've tried to get it working but I can't seem to get any text to flow through to the help file.  Anybody got any tips?  Also in the example shown in the help file the function has an @ sign in front of it.  What does this do?


Ok, I tested it with 3.0 and 2.2.1 and both worked fine.  The only things I can think it can be are...

1.Media isn't in the Media folder in the XCode directory
2.There is a problem with the filename... file names are case sensitive.  It will run on a PC, but when running on a mac it can fail if the filename doesnt match 100%
3 Not sure, but perhaps you are grabbing past the dimensions of the image.

Hi Mike,

I havent used that command yet.  if you have a quick demo I can compile it for you and check.


Just for info.  I ran it using OS 3.0 (as its all I have on my machine) and I only had one very minor leak of about 114 bytes.  This spike happened at the start of the process and then the remaining 7 minutes that I ran the test everything was fine.
No need to apologize, Im very happy things get fixed so quick that I can't keep up :)