GS/HW: Add "Merge Targets" texture-in-RT mode

[stenzek]

Description of Changes

This mode can construct a source from one or more targets currently on the GPU, taking into consideration differing page pitches.

Fixes shadows in Destroy All Humans. Can also be used for Guitar Hero, although that has a bunch of other clear/invalidation issues in play too.

Before:

After:

My rambling about DAH:

so they render the shadow map, and to deal with world-space that fall outside the range, since the PS2 has no "clamp to border colour" option, they need a black rectangle around the shadow map
most games will just draw a 1px line in such cases
but no, this bugger offsets the base pointer by -32 (effectively moving the texture towards the right, with the right most page moving down one row), then redraws it with slightly offset texture coordinates
why they couldn't just offset the coordinates instead of shifting the base pointer?
so I've come up with a convoluted "create a source from multiple targets and local memory" method, that also handles differing page pitches (which is needed for guitar hero)
if I'm going to create a whacky solution, I want it to be applicable to more than one game 😛

Rationale behind Changes

Closes #55.
Closes #785.

Suggested Testing Steps

Test DAH, I'm not sure if the second game is affected though.
Make sure nothing else is broke.
See if anything else can use this fix? (except Guitar Hero).

[seta-san]

oldest bug issue being fixed :)

[yellows111]

Hey, these shadow errors look like what's happening in Poinie's Poin with it's motion blurs with Render Textures enabled. (Was required for a fix for a regression introduced in v1.7.4111 [#8245])

Would this happen to improve that field?

[stenzek]

No, unless it was offsetting BPs backwards, or using different pitches (but that part isn't enabled yet).

[yellows111]

No, unless it was offsetting BPs backwards, or using different pitches (but that part isn't enabled yet).

Just tested this, and your assumption was correct. Still looks like it has a strange dark scanline filter with Merge Targets enabled.

Poinie's Poin_SCPS-15013_20230226152528.gs.gz (Probably won't show the issue like last time)

Regression? HW Renderer bug? I'm lost on this one: Texture corruption just after entering Nasty Sewerage

Poinie's Poin_SCPS-15013_20230226152142.gs.gz

[Dreadmoth]

Test DAH, I'm not sure if the second game is affected though.

Destroy All Humans! 2 is affected. 👍

A small issue remains - shadows in the right-most 64 pixels (native) get stretched (clamped?) to the right edge.

Before:

After:

Software:

GS dump: Destroy All Humans 2 - Make War not Love_SLES-54384_Shadows.gs.gz

[stenzek]

Yeah, I'm aware of the right-side-stretching thing, it affects DAH1 too.

[stenzek]

Right side issues should be fixed now. Also auto enabled the fix for DAH2 in the gamedb.