[d3d9] implement 'clampNegativeLodBias' as a conf option

dxvk.conf

@@ -191,6 +191,15 @@
 # d3d11.samplerLodBias = 0.0
 # d3d9.samplerLodBias = 0.0
 
+
+# Clamps any negative LOD bias to 0. Applies after samplerLodBias has been
+# applied. May help with games that use a high negative LOD bias by default.
+#
+# Supported values: True, False
+
+# d3d9.clampNegativeLodBias = False
+
+
 # Declares vertex positions as invariant in order to solve
 # potential Z-fighting issues at a small performance cost.
 #

src/d3d9/d3d9_device.cpp

@@ -6243,7 +6243,11 @@ namespace dxvk {
       info.mipmapMode     = mipFilter.MipFilter;
       info.maxAnisotropy  = float(cKey.MaxAnisotropy);
       info.useAnisotropy  = cKey.MaxAnisotropy > 1;
+
       info.mipmapLodBias  = cKey.MipmapLodBias + m_d3d9Options.samplerLodBias;
+      if (m_d3d9Options.clampNegativeLodBias)
+        info.mipmapLodBias = std::max(info.mipmapLodBias, 0.0f);
+
       info.mipmapLodMin   = mipFilter.MipsEnabled ? float(cKey.MaxMipLevel) : 0;
       info.mipmapLodMax   = mipFilter.MipsEnabled ? FLT_MAX                 : 0;
       info.reductionMode  = VK_SAMPLER_REDUCTION_MODE_WEIGHTED_AVERAGE;

src/d3d9/d3d9_options.cpp

@@ -75,6 +75,7 @@ namespace dxvk {
     this->textureMemory                 = config.getOption<int32_t>     ("d3d9.textureMemory",                 100) << 20;
     this->deviceLossOnFocusLoss         = config.getOption<bool>        ("d3d9.deviceLossOnFocusLoss",         false);
     this->samplerLodBias                = config.getOption<float>       ("d3d9.samplerLodBias",                0.0f);
+    this->clampNegativeLodBias          = config.getOption<bool>        ("d3d9.clampNegativeLodBias",          false);
 
     // Clamp LOD bias so that people don't abuse this in unintended ways
     this->samplerLodBias = dxvk::fclamp(this->samplerLodBias, -2.0f, 1.0f);

src/d3d9/d3d9_options.h

@@ -141,6 +141,9 @@ namespace dxvk {
     /// Enforces the given LOD bias for all samplers.
     float samplerLodBias;
 
+    /// Clamps negative LOD bias
+    bool clampNegativeLodBias;
+
     /// How much virtual memory will be used for textures (in MB).
     int32_t textureMemory;