Emulator

I have limited graphics knowledge, but this is maybe related/duplicate of #9474 ?

I believe that the issue in 9474 is per pixel, but this issue is per-vertex (for reference, this issue still occurs in the software renderer, but 9474 doesn't.) A very similar fix for vertex normals, binormials, and tangents is already in Dolphin, but not for vertex colors.

I assume this is #8059 / #13184, which is currently worked around with a per-game color fallback in this case instead of trying to preserve the last value.

I thought I tried using a single lingering value and it didn't work for the debug cubes. That was a long time ago though, so maybe I did something wrong.

A dedicated test application would be appreciated.

I remember trying to write one a while back but I just confused myself when trying to determine if it immediately affected other vertices or there was a delay, and which vertex was used. I remember it seeming like there were multiple colors that could be buffered and it would use them in sequence, and I also ended up getting a point to end up showing as two separately colored triangles. It also seemed to vary based on how much data was associated with each vertex (if there were more texture coordinates, it would affect other vertices sooner). I probably still have this test somewhere, but I don't remember exactly where, and I was also messing around with other things (in particular I think I had mismatched color counts between XFMEM_VTXSPECS (0x1008), XFMEM_SETNUMCHAN (0x1009), and BPMEM_GENMODE (0x00)) which may have been more complicated and less useful.

The main quirks that would matter for implementation are if it uses the color from the last drawn vertex, and if that color is immediately used or if it waits a few vertices. (For LIT my somewhat lazy experimentation indicated that it used the last drawn vertex's normal immediately).

I did a quick test with the software renderer:

diff --git a/Source/Core/VideoBackends/Software/SWVertexLoader.cpp b/Source/Core/VideoBackends/Software/SWVertexLoader.cpp
index b655a3143b..f3859c728f 100644
--- a/Source/Core/VideoBackends/Software/SWVertexLoader.cpp
+++ b/Source/Core/VideoBackends/Software/SWVertexLoader.cpp
@@ -167,13 +167,7 @@ static void ReadVertexAttribute(T* dst, DataReader src, const AttributeFormat& f
 static void ParseColorAttributes(InputVertexData* dst, DataReader& src,
                                  const PortableVertexDeclaration& vdec)
 {
-  const auto set_default_color = [](std::array<u8, 4>& color) {
-    color[Tev::ALP_C] = g_ActiveConfig.iMissingColorValue & 0xFF;
-    color[Tev::BLU_C] = (g_ActiveConfig.iMissingColorValue >> 8) & 0xFF;
-    color[Tev::GRN_C] = (g_ActiveConfig.iMissingColorValue >> 16) & 0xFF;
-    color[Tev::RED_C] = (g_ActiveConfig.iMissingColorValue >> 24) & 0xFF;
-  };
-
+  static std::array<std::array<u8, 4>, 2> colors;
   if (vdec.colors[0].enable)
   {
     // Use color0 for channel 0, and color1 for channel 1 if both colors 0 and 1 are present.
@@ -181,7 +175,7 @@ static void ParseColorAttributes(InputVertexData* dst, DataReader& src,
     if (vdec.colors[1].enable)
       ReadVertexAttribute<u8>(dst->color[1].data(), src, vdec.colors[1], 0, 4, true);
     else
-      set_default_color(dst->color[1]);
+      dst->color[1] = colors[1];
   }
   else
   {
@@ -189,9 +183,11 @@ static void ParseColorAttributes(InputVertexData* dst, DataReader& src,
     if (vdec.colors[1].enable)
       ReadVertexAttribute<u8>(dst->color[0].data(), src, vdec.colors[1], 0, 4, true);
     else
-      set_default_color(dst->color[0]);
-    set_default_color(dst->color[1]);
+      dst->color[0] = colors[0];
+    dst->color[1] = colors[1];
   }
+
+  colors = dst->color;
 }
 
 void SWVertexLoader::ParseVertex(const PortableVertexDeclaration& vdec, int index)

The debug cubes in Mario Sunshine were still present, but it did restore the coconut drinks. It also produced accurate results for Lego Indiana Jones (see #12987) and Lloyd from modded brawl (#9268). I can make the same change for the hardware renderers, but doing this will conflict with the current debug cube workaround.

Im also not entirely sure what triggers the lingering either. In my application, if I drew 5 triangles of the eyebrow object (the last object with vertex colors drawn before the textured objcets), then the vertex colors would reset to white on hardware, but if I drew 6, 7, or all 8, then the colors would linger. Perhaps something is overflowing and automatically flushing? Im making stuff up, I have no idea how the FIFO works.

thus my lack of real ability to make a reliable test application. I don't know what triggers the quirk!