[GPU] Apply BaseMap MipFilter via samplers as it may be overridden

Make it have no effect on the texture resource as a resource may be used with samplers with different overrides. Also make sure magnification vs. minification is not undefined with it on Direct3D 12.

src/xenia/gpu/d3d12/d3d12_texture_cache.cc

@@ -971,9 +971,9 @@ D3D12TextureCache::SamplerParameters D3D12TextureCache::GetSamplerParameters(
   parameters.border_color = fetch.border_color;
 
   uint32_t mip_min_level;
-  texture_util::GetSubresourcesFromFetchConstant(
+  texture_util::GetSubresourcesFromFetchConstant(fetch, nullptr, nullptr,
-      fetch, nullptr, nullptr, nullptr, nullptr, nullptr, &mip_min_level,
+                                                 nullptr, nullptr, nullptr,
-      nullptr, binding.mip_filter);
+                                                 &mip_min_level, nullptr);
   parameters.mip_min_level = mip_min_level;
 
   xenos::AnisoFilter aniso_filter =
@@ -982,6 +982,10 @@ D3D12TextureCache::SamplerParameters D3D12TextureCache::GetSamplerParameters(
           : binding.aniso_filter;
   aniso_filter = std::min(aniso_filter, xenos::AnisoFilter::kMax_16_1);
   parameters.aniso_filter = aniso_filter;
+  xenos::TextureFilter mip_filter =
+      binding.mip_filter == xenos::TextureFilter::kUseFetchConst
+          ? fetch.mip_filter
+          : binding.mip_filter;
   if (aniso_filter != xenos::AnisoFilter::kDisabled) {
     parameters.mag_linear = 1;
     parameters.min_linear = 1;
@@ -997,12 +1001,9 @@ D3D12TextureCache::SamplerParameters D3D12TextureCache::GetSamplerParameters(
             ? fetch.min_filter
             : binding.min_filter;
     parameters.min_linear = min_filter == xenos::TextureFilter::kLinear;
-    xenos::TextureFilter mip_filter =
-        binding.mip_filter == xenos::TextureFilter::kUseFetchConst
-            ? fetch.mip_filter
-            : binding.mip_filter;
     parameters.mip_linear = mip_filter == xenos::TextureFilter::kLinear;
   }
+  parameters.mip_base_map = mip_filter == xenos::TextureFilter::kBaseMap;
 
   return parameters;
 }
@@ -1046,7 +1047,7 @@ void D3D12TextureCache::WriteSampler(SamplerParameters parameters,
   desc.AddressU = kAddressModeMap[uint32_t(parameters.clamp_x)];
   desc.AddressV = kAddressModeMap[uint32_t(parameters.clamp_y)];
   desc.AddressW = kAddressModeMap[uint32_t(parameters.clamp_z)];
-  // LOD is calculated in shaders.
+  // LOD biasing is performed in shaders.
   desc.MipLODBias = 0.0f;
   desc.ComparisonFunc = D3D12_COMPARISON_FUNC_NEVER;
   // TODO(Triang3l): Border colors k_ACBYCR_BLACK and k_ACBCRY_BLACK.
@@ -1062,8 +1063,26 @@ void D3D12TextureCache::WriteSampler(SamplerParameters parameters,
     desc.BorderColor[3] = 0.0f;
   }
   desc.MinLOD = float(parameters.mip_min_level);
+  if (parameters.mip_base_map) {
+    // "It is undefined whether LOD clamping based on MinLOD and MaxLOD Sampler
+    // states should happen before or after deciding if magnification is
+    // occuring" - Direct3D 11.3 Functional Specification.
+    // Using the GL_NEAREST / GL_LINEAR minification filter emulation logic
+    // described in the Vulkan VkSamplerCreateInfo specification, preserving
+    // magnification vs. minification - point mip sampling (usable only without
+    // anisotropic filtering on Direct3D 12) and MaxLOD 0.25. With anisotropic
+    // filtering, magnification vs. minification doesn't matter as the filter is
+    // always linear for both on Direct3D 12 - but linear filtering specifically
+    // is what must not be done for kBaseMap, so setting MaxLOD to MinLOD.
+    desc.MaxLOD = desc.MinLOD;
+    if (parameters.aniso_filter == xenos::AnisoFilter::kDisabled) {
+      assert_false(parameters.mip_linear);
+      desc.MaxLOD += 0.25f;
+    }
+  } else {
     // Maximum mip level is in the texture resource itself.
     desc.MaxLOD = FLT_MAX;
+  }
   ID3D12Device* device = command_processor_.GetD3D12Provider().GetDevice();
   device->CreateSampler(&desc, handle);
 }

src/xenia/gpu/d3d12/d3d12_texture_cache.h

@@ -58,7 +58,9 @@ class D3D12TextureCache final : public TextureCache {
       uint32_t mip_linear : 1;              // 14
       xenos::AnisoFilter aniso_filter : 3;  // 17
       uint32_t mip_min_level : 4;           // 21
-      // Maximum mip level is in the texture resource itself.
+      uint32_t mip_base_map : 1;            // 22
+      // Maximum mip level is in the texture resource itself, but mip_base_map
+      // can be used to limit fetching to mip_min_level.
     };
 
     SamplerParameters() : value(0) { static_assert_size(*this, sizeof(value)); }

src/xenia/gpu/texture_util.cc

@@ -23,8 +23,7 @@ void GetSubresourcesFromFetchConstant(
     const xenos::xe_gpu_texture_fetch_t& fetch, uint32_t* width_minus_1_out,
     uint32_t* height_minus_1_out, uint32_t* depth_or_array_size_minus_1_out,
     uint32_t* base_page_out, uint32_t* mip_page_out,
-    uint32_t* mip_min_level_out, uint32_t* mip_max_level_out,
+    uint32_t* mip_min_level_out, uint32_t* mip_max_level_out) {
-    xenos::TextureFilter sampler_mip_filter) {
   uint32_t width_minus_1 = 0;
   uint32_t height_minus_1 = 0;
   uint32_t depth_or_array_size_minus_1 = 0;
@@ -72,16 +71,14 @@ void GetSubresourcesFromFetchConstant(
   }
   uint32_t size_mip_max_level =
       xe::log2_floor(longest_axis_minus_1 + uint32_t(1));
-  xenos::TextureFilter mip_filter =
-      sampler_mip_filter == xenos::TextureFilter::kUseFetchConst
-          ? fetch.mip_filter
-          : sampler_mip_filter;
 
   uint32_t base_page = fetch.base_address & 0x1FFFF;
   uint32_t mip_page = fetch.mip_address & 0x1FFFF;
 
   uint32_t mip_min_level, mip_max_level;
-  if (mip_filter == xenos::TextureFilter::kBaseMap || mip_page == 0) {
+  // Not taking mip_filter == kBaseMap into account for mip_max_level because
+  // the mip filter may be overridden by shader fetch instructions.
+  if (mip_page == 0) {
     mip_min_level = 0;
     mip_max_level = 0;
   } else {

src/xenia/gpu/texture_util.h

@@ -30,9 +30,7 @@ void GetSubresourcesFromFetchConstant(
     const xenos::xe_gpu_texture_fetch_t& fetch, uint32_t* width_minus_1_out,
     uint32_t* height_minus_1_out, uint32_t* depth_or_array_size_minus_1_out,
     uint32_t* base_page_out, uint32_t* mip_page_out,
-    uint32_t* mip_min_level_out, uint32_t* mip_max_level_out,
+    uint32_t* mip_min_level_out, uint32_t* mip_max_level_out);
-    xenos::TextureFilter sampler_mip_filter =
-        xenos::TextureFilter::kUseFetchConst);
 
 // Gets the number of the mipmap level where the packed mips are stored.
 inline uint32_t GetPackedMipLevel(uint32_t width, uint32_t height) {

src/xenia/gpu/xenos.h

@@ -113,7 +113,9 @@ enum class TextureSign : uint32_t {
 enum class TextureFilter : uint32_t {
   kPoint = 0,
   kLinear = 1,
-  kBaseMap = 2,  // Only applicable for mip-filter - always fetch from level 0.
+  // Only applicable to the mip filter - like OpenGL minification filters
+  // GL_NEAREST / GL_LINEAR without MIPMAP_NEAREST / MIPMAP_LINEAR.
+  kBaseMap = 2,
   kUseFetchConst = 3,
 };