shangha3_v.cpp: proposed fix for shangha3 drawing phantom drop shadows for player sprites

[angelosa]

• shangha3 dislikes MAME shadow factor default of 0.6 when drawing player sprite, causing a phantom square shadow when moving player sprite, cfr. screenshot. Setting it to 1.0 prevents it to happen.

[ghost]

isn't setting it to 1.0 just disabling shadows?

maybe there's meant to be some kind of shadow that isn't rendering properly?

[angelosa]

I've already tried to check if there's an extra bit setting in blitter lists (no unknowns) & if bit 0 of paletteram is used for anything (it's not)

1.0 doesn't disable them but makes the ratio to be stronger on the shadow bank.
And from the refs I've saw there's no cursor shadow at all, cfr. MT bug ref

[angelosa]

Also note: there's an extra blink artifact that happens once the continue box appears, something that is fixed again with 1.0 as shadow factor.

[cuavas]

The shadow factor is set as a group contrast value on the underlying palette. This is a simple intensity scale factor – @davidhaywood is right, setting it to 1.0 causes it to have no effect. I don’t think this is really a “fix”.

[angelosa]

So what it could be then, because I'm decidedly lost here. If a set_shadow_factor of 1.0 shouldn't be set in any place then it should throw an exception, but the documentation clearly states that it accept a range of 0.0 - 1.0 ...

[cuavas]

Yes, it accepts a range of 0.0 (shadows are completely black) to 1.0 (shadows have no effect). I haven’t tested it, but it might even be possible to set values larger than 1.0 to cause it to “overdrive” the the shadow instead.

[angelosa]

This is the output with this patch applied. I still see shadows here (because they output thru pen 14). There's chance that the driver is overcomplicating things and this can be done in another way.

[cuavas]

Possibly – maybe it shouldn’t be trying to use the palette shadow feature at all.