The Ocean Hunter Transparency issue

[the_maq]

Any luck with the transparency effects on the stingray and the umi bozo boss or whatever u call it?

[Ian]

No it's currently unemulated.
In fact I think it's the only thing that isn't emulated.
I know roughly how to make it work. But there in lies the problem, I don't know the exact formula they used to calculate model transparency. And that's pretty hard to work out by guess work.

[Bart]

No it's currently unemulated.
In fact I think it's the only thing that isn't emulated.
I know roughly how to make it work. But there in lies the problem, I don't know the exact formula they used to calculate model transparency. And that's pretty hard to work out by guess work.

What is the effect?

[Ian]

Basically they are abusing the LOD tables to do per model transparency. I think it was basically a hack to add transparency dynamically to ROM models. Emergency call ambulance does this too.
Each viewport has an LOD table of like blend in / blend out values. Then the culling nodes have each have an index into this table.
The problem is I can't really make the numbers work. I know the transparency is effected by the viewport angle. Maybe the relationship is 1/angle or something. I'm not sure, I could never make it work.

The model3 isn't the only thing to do transparency like this. Many games blend out models when they reach a certain distance.

[Bart]

Ah, the LOD blending. Now this is probably something we could test once I can transfer code directly from my PC rather than burning EPROMs each time.

So are they blending with an empty model to create a translucency effect?

[Ian]

If we could test on hardware I might be able to figure it out
I have a rough idea how it works.