PixelShaderGen: Pass in LOD bias through PSBlock and use in texture()…

… on some APIs

Source/Core/VideoCommon/ConstantManager.h

@@ -23,6 +23,7 @@ struct PixelShaderConstants
   std::array<int4, 4> kcolors;
   int4 alpha;
   std::array<float4, 8> texdims;
+  std::array<float, 8> lodbias;
   std::array<int4, 2> zbias;
   std::array<int4, 2> indtexscale;
   std::array<int4, 6> indtexmtx;

Source/Core/VideoCommon/PixelShaderGen.cpp

@@ -29,14 +29,15 @@ enum : u32
   C_KCOLORS = C_COLORS + 4,         //  4
   C_ALPHA = C_KCOLORS + 4,          //  8
   C_TEXDIMS = C_ALPHA + 1,          //  9
-  C_ZBIAS = C_TEXDIMS + 8,          // 17
-  C_INDTEXSCALE = C_ZBIAS + 2,      // 19
-  C_INDTEXMTX = C_INDTEXSCALE + 2,  // 21
-  C_FOGCOLOR = C_INDTEXMTX + 6,     // 27
-  C_FOGI = C_FOGCOLOR + 1,          // 28
-  C_FOGF = C_FOGI + 1,              // 29
-  C_ZSLOPE = C_FOGF + 2,            // 31
-  C_EFBSCALE = C_ZSLOPE + 1,        // 32
+  C_LODBIAS = C_TEXDIMS + 8,        // 17
+  C_ZBIAS = C_TEXDIMS + 8,          // 25
+  C_INDTEXSCALE = C_ZBIAS + 2,      // 27
+  C_INDTEXMTX = C_INDTEXSCALE + 2,  // 29
+  C_FOGCOLOR = C_INDTEXMTX + 6,     // 35
+  C_FOGI = C_FOGCOLOR + 1,          // 36
+  C_FOGF = C_FOGI + 1,              // 37
+  C_ZSLOPE = C_FOGF + 2,            // 39
+  C_EFBSCALE = C_ZSLOPE + 1,        // 40
   C_PENVCONST_END = C_EFBSCALE + 1
 };
 
@@ -403,6 +404,7 @@ void WritePixelShaderCommonHeader(ShaderCode& out, APIType api_type,
             "\tint4 " I_KCOLORS "[4];\n"
             "\tint4 " I_ALPHA ";\n"
             "\tfloat4 " I_TEXDIMS "[8];\n"
+            "\tfloat4 " I_LODBIAS "[2];\n"
             "\tint4 " I_ZBIAS "[2];\n"
             "\tint4 " I_INDTEXSCALE "[2];\n"
             "\tint4 " I_INDTEXMTX "[6];\n"
@@ -454,6 +456,33 @@ void WritePixelShaderCommonHeader(ShaderCode& out, APIType api_type,
     out.Write("}};\n");
   }
 
+#ifdef __APPLE__
+  if (api_type == APIType::Vulkan)  // Metal with MoltenVK
+#else
+  if (api_type == APIType::OpenGL && !host_config.backend_sampler_lod_bias)
+#endif
+  {
+    // Metal and OpenGL ES do not support setting the LOD bias value in the sampler, so we pass
+    // it to the fragment shader through the PSBlock and use it as the bias value in the call to
+    // texture().
+    //
+    // I_LODBIAS is defined as a two-element float4 array because SPIRV-Cross will transform an
+    // eight-element float array into an eight-element float4 array due to packing rules.
+    // See: https://github.com/KhronosGroup/SPIRV-Cross/issues/1313
+    //
+    // This helper function calculates the correct array and component indices and returns the
+    // correct lodbias value.
+    out.Write("float lodbias(uint i) {{\n"
+              "\treturn i < 4 ? " I_LODBIAS "[0][i] : " I_LODBIAS "[1][4 - i];\n"
+              "}}\n");
+  }
+  else
+  {
+    // Other APIs can pass in the LOD bias value directly to the sampler, so always return zero.
+    // This should be equivalent to not passing in the LOD bias value at all.
+    out.Write("#define lodbias(i) 0.0\n");
+  }
+
   if (bounding_box)
   {
     if (api_type == APIType::D3D)
@@ -1451,6 +1480,7 @@ static void SampleTexture(ShaderCode& out, std::string_view texcoords, std::stri
                           int texmap, bool stereo, APIType api_type)
 {
   out.SetConstantsUsed(C_TEXDIMS + texmap, C_TEXDIMS + texmap);
+  out.SetConstantsUsed(C_LODBIAS + texmap, C_LODBIAS + texmap);
 
   if (api_type == APIType::D3D)
   {
@@ -1460,8 +1490,9 @@ static void SampleTexture(ShaderCode& out, std::string_view texcoords, std::stri
   }
   else
   {
-    out.Write("iround(255.0 * texture(samp[{}], float3({}.xy * " I_TEXDIMS "[{}].xy, {}))).{};\n",
-              texmap, texcoords, texmap, stereo ? "layer" : "0.0", texswap);
+    out.Write("iround(255.0 * texture(samp[{}], float3({}.xy * " I_TEXDIMS
+              "[{}].xy, {}), lodbias({}u))).{};\n",
+              texmap, texcoords, texmap, stereo ? "layer" : "0.0", texmap, texswap);
   }
 }
 

Source/Core/VideoCommon/PixelShaderManager.cpp

@@ -286,6 +286,12 @@ void PixelShaderManager::SetTexDims(int texmapid, u32 width, u32 height)
   constants.texdims[texmapid][1] = rheight;
 }
 
+void PixelShaderManager::SetLodBias(int texmapid, float bias)
+{
+  constants.lodbias[texmapid] = bias;
+  dirty = true;
+}
+
 void PixelShaderManager::SetZTextureBias()
 {
   constants.zbias[1][3] = bpmem.ztex1.bias;

Source/Core/VideoCommon/PixelShaderManager.h

@@ -31,6 +31,7 @@ class PixelShaderManager
   static void SetAlphaTestChanged();
   static void SetDestAlphaChanged();
   static void SetTexDims(int texmapid, u32 width, u32 height);
+  static void SetLodBias(int texmapid, float bias);
   static void SetZTextureBias();
   static void SetViewportChanged();
   static void SetEfbScaleChanged(float scalex, float scaley);

Source/Core/VideoCommon/ShaderGenCommon.h

@@ -202,6 +202,7 @@ const char* GetInterpolationQualifier(bool msaa, bool ssaa, bool in_glsl_interfa
 #define I_KCOLORS "k"
 #define I_ALPHA "alphaRef"
 #define I_TEXDIMS "texdim"
+#define I_LODBIAS "clodbias"
 #define I_ZBIAS "czbias"
 #define I_INDTEXSCALE "cindscale"
 #define I_INDTEXMTX "cindmtx"

Source/Core/VideoCommon/TextureCacheBase.cpp

@@ -1025,6 +1025,8 @@ static void SetSamplerState(u32 index, float custom_tex_scale, bool custom_tex,
     state.anisotropic_filtering = 0;
   }
 
+  PixelShaderManager::SetLodBias(index, state.lod_bias / 256.0f);
+
   g_renderer->SetSamplerState(index, state);
 }
 

Source/Core/VideoCommon/UberShaderPixel.cpp

@@ -259,7 +259,7 @@ ShaderCode GenPixelShader(APIType ApiType, const ShaderHostConfig& host_config,
     // supports this in the future.
     out.Write("int4 sampleTexture(uint sampler_num, float3 uv) {{\n");
     if (ApiType == APIType::OpenGL || ApiType == APIType::Vulkan)
-      out.Write("  return iround(texture(samp[sampler_num], uv) * 255.0);\n");
+      out.Write("  return iround(texture(samp[sampler_num], uv, lodbias(sampler_num)) * 255.0);\n");
     else if (ApiType == APIType::D3D)
       out.Write("  return iround(Tex[sampler_num].Sample(samp[sampler_num], uv) * 255.0);\n");
     out.Write("}}\n\n");
@@ -275,7 +275,8 @@ ShaderCode GenPixelShader(APIType ApiType, const ShaderHostConfig& host_config,
     for (int i = 0; i < 8; i++)
     {
       if (ApiType == APIType::OpenGL || ApiType == APIType::Vulkan)
-        out.Write("  case {}u: return iround(texture(samp[{}], uv) * 255.0);\n", i, i);
+        out.Write("  case {}u: return iround(texture(samp[{}], uv, lodbias({}u)) * 255.0);\n", i, i,
+                  i);
       else if (ApiType == APIType::D3D)
         out.Write("  case {}u: return iround(Tex[{}].Sample(samp[{}], uv) * 255.0);\n", i, i, i);
     }