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Graphics > Putting Backdrop in front of Background?

#173216 - brave_orakio - Sat Mar 27, 2010 3:28 pm

is this possible? There is a register for BD in REG_ALPHABLEND in the A layer(top layer). So is it possible?
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#173217 - FluBBa - Sat Mar 27, 2010 3:46 pm

Or you can just disable the background? What do you want to achieve?
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#173231 - brave_orakio - Sun Mar 28, 2010 12:18 pm

I actually want to blend it with BG0 ang BG1 so I don't have to use one more BG to do it.

I noticed that the backdrop changes color depending on index 0 of BG palette. But I have found no tutorial that says I can but the backdrop in front. Just that REG_BLDALPHA has an entry for BD in layer A.
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help me

#173237 - Kyoufu Kawa - Sun Mar 28, 2010 2:22 pm

Backdrop's the backdrop. You don't put a solid chunk of color the size of the screen in front of everything else.

I think it's only there in the top blend settings to balance out against the bottoms.

#173240 - FluBBa - Sun Mar 28, 2010 7:30 pm

Yes, I see your problem...
Since the GBA can only blend 2 layers per pixel you will get problem when you have BG0 & BG1 over each other since they then will blend with each other and not the backdrop.
And there is no way to go around that.
But if you want to change all the colors on screen I guess you can write your own palette blending routine.
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#173251 - brave_orakio - Mon Mar 29, 2010 2:01 am

Ah I see. No way around it I guess. I really do need to use a 3rd BG for what I plan to do.

Thanks anyway, I just found it strange that the BD would have an entry in REG_BLDALPHA for layer A when I can think of no way to put the BD in fornt of any of the other layers.
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#173267 - FluBBa - Mon Mar 29, 2010 12:07 pm

The reason for BD to be in layer A/1st target is because it can be used for brightness increase/decrease.
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#173289 - brave_orakio - Tue Mar 30, 2010 1:59 am

Oh, I see. Using the white/black blending(fade to white/black)?
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#173294 - FluBBa - Tue Mar 30, 2010 9:35 am

yes.
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I probably suck, my not is a programmer.