From 8af8ad38406c35182dcb23a3c511be007a87dd9c Mon Sep 17 00:00:00 2001
From: AnyOldName3 <krizdjali+github@gmail.com>
Date: Wed, 20 Jan 2021 01:17:16 +0000
Subject: [PATCH] Always write opaque fragments instead of relying on blending
 being off for translucent RTT

---
 apps/openmw/mwrender/characterpreview.cpp | 26 +++++++++++++++++++++--
 apps/openmw/mwrender/renderingmanager.cpp |  1 +
 files/shaders/objects_fragment.glsl       |  4 ++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/apps/openmw/mwrender/characterpreview.cpp b/apps/openmw/mwrender/characterpreview.cpp
index 89db3e5f46..f21e667eb0 100644
--- a/apps/openmw/mwrender/characterpreview.cpp
+++ b/apps/openmw/mwrender/characterpreview.cpp
@@ -5,6 +5,7 @@
 #include <osg/Material>
 #include <osg/Fog>
 #include <osg/BlendFunc>
+#include <osg/TexEnvCombine>
 #include <osg/Texture2D>
 #include <osg/Camera>
 #include <osg/PositionAttitudeTransform>
@@ -85,7 +86,7 @@ namespace MWRender
     class SetUpBlendVisitor : public osg::NodeVisitor
     {
     public:
-        SetUpBlendVisitor(): osg::NodeVisitor(TRAVERSE_ALL_CHILDREN)
+        SetUpBlendVisitor(): osg::NodeVisitor(TRAVERSE_ALL_CHILDREN), mNoAlphaUniform(new osg::Uniform("noAlpha", false))
         {
         }
 
@@ -102,10 +103,17 @@ namespace MWRender
                     newStateSet->setAttribute(newBlendFunc, osg::StateAttribute::ON);
                     node.setStateSet(newStateSet);
                 }
-
+                if (stateset->getMode(GL_BLEND) & osg::StateAttribute::ON)
+                {
+                    // Disable noBlendAlphaEnv
+                    stateset->setTextureMode(7, GL_TEXTURE_2D, osg::StateAttribute::OFF);
+                    stateset->addUniform(mNoAlphaUniform);
+                }
             }
             traverse(node);
         }
+    private:
+        osg::ref_ptr<osg::Uniform> mNoAlphaUniform;
     };
 
     CharacterPreview::CharacterPreview(osg::Group* parent, Resource::ResourceSystem* resourceSystem,
@@ -164,6 +172,20 @@ namespace MWRender
         fog->setEnd(10000000);
         stateset->setAttributeAndModes(fog, osg::StateAttribute::OFF|osg::StateAttribute::OVERRIDE);
 
+        // Opaque stuff must have 1 as its fragment alpha as the FBO is translucent, so having blending off isn't enough
+        osg::ref_ptr<osg::TexEnvCombine> noBlendAlphaEnv = new osg::TexEnvCombine();
+        noBlendAlphaEnv->setCombine_Alpha(osg::TexEnvCombine::REPLACE);
+        noBlendAlphaEnv->setSource0_Alpha(osg::TexEnvCombine::CONSTANT);
+        noBlendAlphaEnv->setConstantColor(osg::Vec4(0.0, 0.0, 0.0, 1.0));
+        noBlendAlphaEnv->setCombine_RGB(osg::TexEnvCombine::REPLACE);
+        noBlendAlphaEnv->setSource0_RGB(osg::TexEnvCombine::PREVIOUS);
+        osg::ref_ptr<osg::Texture2D> dummyTexture = new osg::Texture2D();
+        dummyTexture->setInternalFormat(GL_RED);
+        dummyTexture->setTextureSize(1, 1);
+        stateset->setTextureAttributeAndModes(7, dummyTexture, osg::StateAttribute::ON);
+        stateset->setTextureAttribute(7, noBlendAlphaEnv, osg::StateAttribute::ON);
+        stateset->addUniform(new osg::Uniform("noAlpha", true));
+
         osg::ref_ptr<osg::LightModel> lightmodel = new osg::LightModel;
         lightmodel->setAmbientIntensity(osg::Vec4(0.0, 0.0, 0.0, 1.0));
         stateset->setAttributeAndModes(lightmodel, osg::StateAttribute::ON);
diff --git a/apps/openmw/mwrender/renderingmanager.cpp b/apps/openmw/mwrender/renderingmanager.cpp
index 6ce431d2e2..e1f6f0dd96 100644
--- a/apps/openmw/mwrender/renderingmanager.cpp
+++ b/apps/openmw/mwrender/renderingmanager.cpp
@@ -370,6 +370,7 @@ namespace MWRender
         mRootNode->getOrCreateStateSet()->addUniform(new osg::Uniform("near", mNearClip));
         mRootNode->getOrCreateStateSet()->addUniform(new osg::Uniform("far", mViewDistance));
         mRootNode->getOrCreateStateSet()->addUniform(new osg::Uniform("simpleWater", false));
+        mRootNode->getOrCreateStateSet()->addUniform(new osg::Uniform("noAlpha", false));
 
         mUniformNear = mRootNode->getOrCreateStateSet()->getUniform("near");
         mUniformFar = mRootNode->getOrCreateStateSet()->getUniform("far");
diff --git a/files/shaders/objects_fragment.glsl b/files/shaders/objects_fragment.glsl
index 78660685f6..bd2bd5909f 100644
--- a/files/shaders/objects_fragment.glsl
+++ b/files/shaders/objects_fragment.glsl
@@ -50,6 +50,7 @@ uniform mat2 bumpMapMatrix;
 #endif
 
 uniform bool simpleWater;
+uniform bool noAlpha;
 
 varying float euclideanDepth;
 varying float linearDepth;
@@ -208,5 +209,8 @@ void main()
 #endif
     gl_FragData[0].xyz = mix(gl_FragData[0].xyz, gl_Fog.color.xyz, fogValue);
 
+    if (noAlpha)
+        gl_FragData[0].a = 1.0;
+
     applyShadowDebugOverlay();
 }