MSAA is a optimiztion to execute the fragment shader just once per pixel instead per sample.
It sounds great, but has a big issue: At edges where the center isn't in the polygon, the
fragment would still be executed, but still with the center of the pixel as position.
So if some calculations aren't allowed outside the polygon, the result would be invalid.
But the nice one: we can give a hint to each input to be choosen from a valid pixel,
so now every pixel will be calculated with valid source.
At the end of July 2011, LM published a free DSP ROM that works with games
using the Zelda UCode. His ROM only has the code to handle UCode loading and a
few utility functions, the rest is missing. This includes the four large sound
mixing functions used by the AX UCode and the DROM containing coefficients used
for polyphase resampling in AX.
This is an improved, updated version of this ROM, which changes the following:
- We now have a free DROM that works for polyphase resampling by "emulating"
linear interpolation. The coefficients contained in the DROM are normally a
list of { c1, c2, c3, c4 } which are used to interpolate a sample value from
four previous samples:
out_sample = prev1 * c1 + prev2 * c2 + prev3 * c3 + prev4 * c4
The coefficients are chosen depending on the fractional part of the current
position (basically, our position between the previous and the next sample).
We can use this fact to generate (c1, c2, c3, c4) for each possible
fractional part so that:
out_sample = prev3 * curr_pos + prev4 * (1 - curr_pos)
Which is the formula for linear interpolation between prev3 and prev4. Linear
interpolation is not as good as polyphase resampling but it still works very
well and I couldn't really hear any difference between the two. If someone
wants to generate real polyphase filter coefficients, they are welcome to
submit a patch.
- The IROM now contains the 4 mixing functions used by the AX UCode: mix_add,
mix_add_two, mix_add_ramp, mix_add_ramp_two. They are large, inlined
functions (probably for performance reasons) in the official DSP IROM, our
version prefers to use a loop. This *should* be more performant with our DSP
JIT implementation, but I did not benchmark that.
Because the new DSP ROM is working just as well as the official ROM in 95% of
cases, it is now shipped by default with Dolphin and will be used with DSPLLE
if you don't have an official DSP ROM in User/GC. It will still display a panic
alert at every boot to notice you that you are using a non official DSP ROM
made by us, which is not perfect.
Games using the CARD, IPL or GBA UCodes are still broken. I don't know what
games this actually impacts, but this is a very small proportion compared to
what works.
Merge an endless story. The branch name is a lie, it was started as glsl, but now it is a complete reworked opengl3 backend.
It just began with simple changes which aren't supported on osx.
They either support ogl2 OR ogl3 core, but mixing isn't allowed.
As the branch name says, the vicious circle starts with GLSL, but just implementing one wasn't possible either:
- OSX supports only GLSL100 which doesn't support our shaders.
- Vertex Array Objects are needed for ogl3, but not supported on ogl2
- immediate mode isn't supported any more, so we must implement vertex buffers
- uniform buffers are recommended as else we would need tons glUniform
- postprocessing shaders have to be converted to glsl
- lots of smaller outdated issues and bug fixes :-)
Thanks at all for testing and at Sonic for converting all of our shaders to glsl130
And sorry for all upcoming bugs...
Ryan Houdek