Broken alpha blending in Tomb Raider 1

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Groel
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Joined: Sun Jun 08, 2014 2:02 pm

Broken alpha blending in Tomb Raider 1

Postby Groel » Sun Jun 08, 2014 2:16 pm

Hello there.

This is my first time using nGlide and I can't seem to get alpha blending working correctly in Tomb Raider 1 (official 3dfx patch)

Unfortunately, I don't have any more games handy so I can't tell if it's a TR1-only issue.

Notice the ugly sharp edges on the sprites. This is a 100% off from what it looked like on my real Voodoo1-powered Pentium back in the the day.

You'd normally expect to see the edges of the sprites blending smoothly with the background, and that used to be the standard.

Am I missing something here?

I'm running the latest nGlide + latest DOSBox SVN Daum on Win7 64bit.

Thanks for your time and thanks for this nice piece of software.
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Zeus
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Re: Broken alpha blending in Tomb Raider 1

Postby Zeus » Sun Jun 08, 2014 3:03 pm

You need to use Rush patch if you want to use nGlide. Original patch is statically linked.

Also, make sure "glide" setting is set to true in dosbox.conf.

Groel
Posts: 2
Joined: Sun Jun 08, 2014 2:02 pm

Re: Broken alpha blending in Tomb Raider 1

Postby Groel » Sun Jun 08, 2014 5:47 pm

Alright, thank you for the hint, but I'm afraid it didn't fix it.

What I'm getting now are the very same solid, opaque, sharp edges except they're no longer outlined ("darkened" if you will). The blending between the sprite and the background is still not happening the way it should. It kind of reminds me of old time glide wrapper artifacts from the post-paletted texture era.

On a side note, the screenshot feature in DosBox does't work correctly with this patch (green screen) so I can't even show you exactly what it looks like.

Regards.

Binary Bob
Posts: 16
Joined: Tue Oct 07, 2014 8:41 am

Re: Broken alpha blending in Tomb Raider 1

Postby Binary Bob » Tue Oct 07, 2014 8:53 am

Mystery resolved. It was the PowerVR exe which actually utilized that enhanced type of alpha blending, as well as sprite filtering, which too is absent when running the 3dfx version.

Nothing wrong with nGlide whatsoever, it does indeed look as it's supposed to look.

Check out this vid and pay attention to the water reflections for the PowerVR part; there's your alpha blending.

https://www.youtube.com/watch?v=5GMesT4WKzI

Binary Bob
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Joined: Tue Oct 07, 2014 8:41 am

Re: Broken alpha blending in Tomb Raider 1

Postby Binary Bob » Wed Mar 25, 2015 10:29 am

It just hit me today how cool it would be to have an option for forcing this type of alpha blending. I'm not familiar at all with the inner works of 3dfx hardware, but since this type of alpha blending does indeed exist in standard voodoo cards and is used in early glide-powered titles such as Carmageddon, I'd presume we're talking some kind of flag that would have to be toggled somewhere?

Just a thought :)

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Zeus
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Re: Broken alpha blending in Tomb Raider 1

Postby Zeus » Wed Mar 25, 2015 10:52 pm

Don't want to sound harsh, but things like this are very time consuming and I highly doubt anybody will do this for you.



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