From 9c94058727880eabc41c5d48b2f853eeb4c3e4a8 Mon Sep 17 00:00:00 2001
From: Alexei Kotov <alexdobrohotov@yandex.ru>
Date: Sat, 4 Nov 2023 20:02:55 +0300
Subject: [PATCH] Support Oblivion parallax setup

---
 components/nifosg/nifloader.cpp          |  1 +
 components/shader/shadervisitor.cpp      | 10 +++++++
 components/shader/shadervisitor.hpp      |  1 +
 files/shaders/compatibility/objects.frag | 35 ++++++++++++++++--------
 4 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/components/nifosg/nifloader.cpp b/components/nifosg/nifloader.cpp
index 17c608f2d4..436f2e1d34 100644
--- a/components/nifosg/nifloader.cpp
+++ b/components/nifosg/nifloader.cpp
@@ -2363,6 +2363,7 @@ namespace NifOsg
                     osg::StateSet* stateset = node->getOrCreateStateSet();
                     handleTextureProperty(
                         texprop, node->getName(), stateset, composite, imageManager, boundTextures, animflags);
+                    node->setUserValue("applyMode", static_cast<int>(texprop->mApplyMode));
                     break;
                 }
                 case Nif::RC_BSShaderPPLightingProperty:
diff --git a/components/shader/shadervisitor.cpp b/components/shader/shadervisitor.cpp
index 96e3d42f78..a08652620d 100644
--- a/components/shader/shadervisitor.cpp
+++ b/components/shader/shadervisitor.cpp
@@ -181,6 +181,7 @@ namespace Shader
         , mAlphaBlend(false)
         , mBlendFuncOverridden(false)
         , mAdditiveBlending(false)
+        , mDiffuseHeight(false)
         , mNormalHeight(false)
         , mTexStageRequiringTangents(-1)
         , mSoftParticles(false)
@@ -303,6 +304,14 @@ namespace Shader
         if (node.getUserValue(Misc::OsgUserValues::sXSoftEffect, softEffect) && softEffect)
             mRequirements.back().mSoftParticles = true;
 
+        int applyMode;
+        // Oblivion parallax
+        if (node.getUserValue("applyMode", applyMode) && applyMode == 4)
+        {
+            mRequirements.back().mShaderRequired = true;
+            mRequirements.back().mDiffuseHeight = true;
+        }
+
         // Make sure to disregard any state that came from a previous call to createProgram
         osg::ref_ptr<AddedState> addedState = getAddedState(*stateset);
 
@@ -615,6 +624,7 @@ namespace Shader
             addedState->addUniform("useDiffuseMapForShadowAlpha");
         }
 
+        defineMap["diffuseParallax"] = reqs.mDiffuseHeight ? "1" : "0";
         defineMap["parallax"] = reqs.mNormalHeight ? "1" : "0";
 
         writableStateSet->addUniform(new osg::Uniform("colorMode", reqs.mColorMode));
diff --git a/components/shader/shadervisitor.hpp b/components/shader/shadervisitor.hpp
index 66bd8c2a9d..a8e79ec995 100644
--- a/components/shader/shadervisitor.hpp
+++ b/components/shader/shadervisitor.hpp
@@ -108,6 +108,7 @@ namespace Shader
             bool mBlendFuncOverridden;
             bool mAdditiveBlending;
 
+            bool mDiffuseHeight; // true if diffuse map has height info in alpha channel
             bool mNormalHeight; // true if normal map has height info in alpha channel
 
             // -1 == no tangents required
diff --git a/files/shaders/compatibility/objects.frag b/files/shaders/compatibility/objects.frag
index b86678af87..6de1f6d02f 100644
--- a/files/shaders/compatibility/objects.frag
+++ b/files/shaders/compatibility/objects.frag
@@ -113,10 +113,6 @@ void main()
     applyOcclusionDiscard(orthoDepthMapCoord, texture2D(orthoDepthMap, orthoDepthMapCoord.xy * 0.5 + 0.5).r);
 #endif
 
-#if @diffuseMap
-    vec2 adjustedDiffuseUV = diffuseMapUV;
-#endif
-
     vec3 normal = normalize(passNormal);
     vec3 viewVec = normalize(passViewPos.xyz);
 
@@ -131,11 +127,24 @@ void main()
     normal = normalize(tbnTranspose * (normalTex.xyz * 2.0 - 1.0));
 #endif
 
-#if @parallax
+#if !@diffuseMap
+    gl_FragData[0] = vec4(1.0);
+#else
+    vec2 adjustedDiffuseUV = diffuseMapUV;
+
+#if @normalMap && (@parallax || @diffuseParallax)
     vec3 cameraPos = (gl_ModelViewMatrixInverse * vec4(0,0,0,1)).xyz;
     vec3 objectPos = (gl_ModelViewMatrixInverse * vec4(passViewPos, 1)).xyz;
     vec3 eyeDir = normalize(cameraPos - objectPos);
-    vec2 offset = getParallaxOffset(eyeDir, tbnTranspose, normalTex.a, (passTangent.w > 0.0) ? -1.f : 1.f);
+#if @parallax
+    float height = normalTex.a;
+    float flipY = (passTangent.w > 0.0) ? -1.f : 1.f;
+#else
+    float height = texture2D(diffuseMap, diffuseMapUV).a;
+    // FIXME: shouldn't be necessary, but in this path false-positives are common
+    float flipY = -1.f;
+#endif
+    vec2 offset = getParallaxOffset(eyeDir, tbnTranspose, height, flipY);
     adjustedDiffuseUV += offset; // only offset diffuse for now, other textures are more likely to be using a completely different UV set
 
     // TODO: check not working as the same UV buffer is being bound to different targets
@@ -149,14 +158,16 @@ void main()
 
 #endif
 
-vec3 viewNormal = normalize(gl_NormalMatrix * normal);
-
-#if @diffuseMap
-    gl_FragData[0] = texture2D(diffuseMap, adjustedDiffuseUV);
-    gl_FragData[0].a *= coveragePreservingAlphaScale(diffuseMap, adjustedDiffuseUV);
+    vec4 diffuseTex = texture2D(diffuseMap, adjustedDiffuseUV);
+    gl_FragData[0].xyz = diffuseTex.xyz;
+#if !@diffuseParallax
+    gl_FragData[0].a = diffuseTex.a * coveragePreservingAlphaScale(diffuseMap, adjustedDiffuseUV);
 #else
-    gl_FragData[0] = vec4(1.0);
+    gl_FragData[0].a = 1.0;
 #endif
+#endif
+
+    vec3 viewNormal = normalize(gl_NormalMatrix * normal);
 
     vec4 diffuseColor = getDiffuseColor();
     gl_FragData[0].a *= diffuseColor.a;