Don't use FFP-friendly texture image units for shadow maps

This more-or-less gets rid of the shadow system's only depencency on FFP
stuff. All that remains is it using OSG cameras, which OSG provides a
uniform-based implementation of, too, which we can trivially migrate to.

This should mean we're not eating any of the ~8 FPP-friendly texture
units, which is good as Morrowind models can use all of those on their
(although they very rarely do), and instead use some of the ~160
shader-only texture image units. This just requires not calling
glEnable(GL_TEXTURE_2D), accomplished by changing
setTextureAttributeAndModes to setTextureAttribute.

Also changes from using glTexGen and its eye plane matrices to pass the
shadow space matrix for each light to explicit uniforms. Thankfully, the
maths was a simple combination of the valid region matrix and eye plane
matrix maths.

As of this commit, I believe this kills shadows in one eye for stereo
rendering.

components/sceneutil/mwshadowtechnique.cpp

@@ -537,9 +537,6 @@ MWShadowTechnique::ShadowData::ShadowData(MWShadowTechnique::ViewDependentData*
 
     bool debug = settings->getDebugDraw();
 
-    // set up texgen
-    _texgen = new osg::TexGen;
-
     // set up the texture
     _texture = new osg::Texture2D;
 
@@ -994,8 +991,6 @@ void SceneUtil::MWShadowTechnique::copyShadowMap(osgUtil::CullVisitor& cv, ViewD
         sdl.push_back(lhs_sd);
     }
 
-    assignTexGenSettings(cv, lhs);
-
     if (lhs->_numValidShadows > 0)
     {
         prepareStateSetForRenderingShadow(*lhs, cv.getTraversalNumber());
@@ -1007,13 +1002,6 @@ void SceneUtil::MWShadowTechnique::setCustomFrustumCallback(CustomFrustumCallbac
     _customFrustumCallback = cfc;
 }
 
-void SceneUtil::MWShadowTechnique::assignTexGenSettings(osgUtil::CullVisitor& cv, ViewDependentData* vdd)
-{
-    for (const auto& sd : vdd->getShadowDataList())
-    {
-        assignTexGenSettings(&cv, sd->_camera, sd->_textureUnit, sd->_texgen);
-    }
-}
 
 void MWShadowTechnique::update(osg::NodeVisitor& nv)
 {
@@ -1035,7 +1023,7 @@ void MWShadowTechnique::cull(osgUtil::CullVisitor& cv)
             int endUnit = baseUnit + settings->getNumShadowMapsPerLight();
             for (int i = baseUnit; i < endUnit; ++i)
             {
-                dummyState->setTextureAttributeAndModes(i, _fallbackShadowMapTexture, osg::StateAttribute::ON);
+                dummyState->setTextureAttribute(i, _fallbackShadowMapTexture, osg::StateAttribute::ON);
                 dummyState->addUniform(new osg::Uniform(("shadowTexture" + std::to_string(i - baseUnit)).c_str(), i));
                 dummyState->addUniform(new osg::Uniform(("shadowTextureUnit" + std::to_string(i - baseUnit)).c_str(), i));
             }
@@ -1548,7 +1536,30 @@ void MWShadowTechnique::cull(osgUtil::CullVisitor& cv)
  
             // 4.4 compute main scene graph TexGen + uniform settings + setup state
             //
-            assignTexGenSettings(&cv, camera.get(), textureUnit, sd->_texgen.get());
+            {
+                osg::Matrix shadowSpaceMatrix = cv.getCurrentCamera()->getInverseViewMatrix() *
+                    camera->getViewMatrix() *
+                    camera->getProjectionMatrix() *
+                    osg::Matrix::translate(1.0,1.0,1.0) *
+                    osg::Matrix::scale(0.5,0.5,0.5);
+
+                std::string shadowSpaceUniformName = "shadowSpaceMatrix" + std::to_string(sm_i);
+                osg::ref_ptr<osg::Uniform> shadowSpaceUniform;
+
+                for (const auto & uniform : _uniforms[cv.getTraversalNumber() % 2])
+                {
+                    if (uniform->getName() == shadowSpaceUniformName)
+                        shadowSpaceUniform = uniform;
+                }
+
+                if (!shadowSpaceUniform)
+                {
+                    shadowSpaceUniform = new osg::Uniform(osg::Uniform::FLOAT_MAT4, shadowSpaceUniformName);
+                    _uniforms[cv.getTraversalNumber() % 2].push_back(shadowSpaceUniform);
+                }
+
+                shadowSpaceUniform->set(shadowSpaceMatrix);
+            }
 
             // mark the light as one that has active shadows and requires shaders
             pl.textureUnits.push_back(textureUnit);
@@ -1556,14 +1567,7 @@ void MWShadowTechnique::cull(osgUtil::CullVisitor& cv)
             // pass on shadow data to ShadowDataList
             sd->_textureUnit = textureUnit;
 
-            if (textureUnit >= 8)
+            sdl.push_back(sd);
-            {
-                OSG_NOTICE<<"Shadow texture unit is invalid for texgen, will not be used."<<std::endl;
-            }
-            else
-            {
-                sdl.push_back(sd);
-            }
 
             // increment counters.
             ++textureUnit;
@@ -1764,7 +1768,7 @@ void MWShadowTechnique::createShaders()
     // Always use the GL_ALWAYS shader as the shadows bin will change it if necessary
     _shadowCastingStateSet->setAttributeAndModes(_castingPrograms[GL_ALWAYS - GL_NEVER], osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
     // The casting program uses a sampler, so to avoid undefined behaviour, we must bind a dummy texture in case no other is supplied
-    _shadowCastingStateSet->setTextureAttributeAndModes(0, _fallbackBaseTexture.get(), osg::StateAttribute::ON);
+    _shadowCastingStateSet->setTextureAttribute(0, _fallbackBaseTexture.get(), osg::StateAttribute::ON);
     _shadowCastingStateSet->addUniform(new osg::Uniform("useDiffuseMapForShadowAlpha", true));
     _shadowCastingStateSet->addUniform(new osg::Uniform("alphaTestShadows", false));
     osg::ref_ptr<osg::Depth> depth = new osg::Depth;
@@ -3081,28 +3085,6 @@ bool MWShadowTechnique::adjustPerspectiveShadowMapCameraSettings(osgUtil::Render
     return true;
 }
 
-bool MWShadowTechnique::assignTexGenSettings(osgUtil::CullVisitor* cv, osg::Camera* camera, unsigned int textureUnit, osg::TexGen* texgen)
-{
-    OSG_INFO<<"assignTexGenSettings() textureUnit="<<textureUnit<<" texgen="<<texgen<<std::endl;
-
-    texgen->setMode(osg::TexGen::EYE_LINEAR);
-
-    // compute the matrix which takes a vertex from local coords into tex coords
-    // We actually use two matrices one used to define texgen
-    // and second that will be used as modelview when appling to OpenGL
-    texgen->setPlanesFromMatrix( camera->getProjectionMatrix() *
-                                 osg::Matrix::translate(1.0,1.0,1.0) *
-                                 osg::Matrix::scale(0.5,0.5,0.5) );
-
-    // Place texgen with modelview which removes big offsets (making it float friendly)
-    osg::ref_ptr<osg::RefMatrix> refMatrix =
-        new osg::RefMatrix( camera->getInverseViewMatrix() * (*(cv->getModelViewMatrix())) );
-
-    osgUtil::RenderStage* currentStage = cv->getCurrentRenderBin()->getStage();
-    currentStage->getPositionalStateContainer()->addPositionedTextureAttribute( textureUnit, refMatrix.get(), texgen );
-    return true;
-}
-
 void MWShadowTechnique::cullShadowReceivingScene(osgUtil::CullVisitor* cv) const
 {
     OSG_INFO<<"cullShadowReceivingScene()"<<std::endl;
@@ -3196,12 +3178,7 @@ osg::StateSet* MWShadowTechnique::prepareStateSetForRenderingShadow(ViewDependen
 
         OSG_INFO<<"   ShadowData for "<<sd._textureUnit<<std::endl;
 
-        stateset->setTextureAttributeAndModes(sd._textureUnit, sd._texture.get(), shadowMapModeValue);
+        stateset->setTextureAttribute(sd._textureUnit, sd._texture.get(), shadowMapModeValue);
-
-        stateset->setTextureMode(sd._textureUnit,GL_TEXTURE_GEN_S,osg::StateAttribute::ON);
-        stateset->setTextureMode(sd._textureUnit,GL_TEXTURE_GEN_T,osg::StateAttribute::ON);
-        stateset->setTextureMode(sd._textureUnit,GL_TEXTURE_GEN_R,osg::StateAttribute::ON);
-        stateset->setTextureMode(sd._textureUnit,GL_TEXTURE_GEN_Q,osg::StateAttribute::ON);
     }
 
     return stateset;
@@ -3304,7 +3281,7 @@ void SceneUtil::MWShadowTechnique::DebugHUD::draw(osg::ref_ptr<osg::Texture2D> t
         addAnotherShadowMap();
     
     osg::ref_ptr<osg::StateSet> stateSet = new osg::StateSet();
-    stateSet->setTextureAttributeAndModes(sDebugTextureUnit, texture, osg::StateAttribute::ON);
+    stateSet->setTextureAttribute(sDebugTextureUnit, texture, osg::StateAttribute::ON);
 
     auto frustumUniform = mFrustumUniforms[cv.getTraversalNumber() % 2][shadowMapNumber];
     frustumUniform->set(matrix);
@@ -3317,8 +3294,6 @@ void SceneUtil::MWShadowTechnique::DebugHUD::draw(osg::ref_ptr<osg::Texture2D> t
     mDebugCameras[shadowMapNumber]->accept(cv);
     cv.popStateSet();
     cv.setTraversalMask(traversalMask);
-
-    // cv.getState()->setCheckForGLErrors(osg::State::ONCE_PER_ATTRIBUTE);
 }
 
 void SceneUtil::MWShadowTechnique::DebugHUD::releaseGLObjects(osg::State* state) const

components/sceneutil/mwshadowtechnique.hpp

@@ -193,7 +193,6 @@ namespace SceneUtil {
 
             unsigned int                        _textureUnit;
             osg::ref_ptr<osg::Texture2D>        _texture;
-            osg::ref_ptr<osg::TexGen>           _texgen;
             osg::ref_ptr<osg::Camera>           _camera;
         };
 
@@ -241,8 +240,6 @@ namespace SceneUtil {
 
         void setCustomFrustumCallback(CustomFrustumCallback* cfc);
 
-        void assignTexGenSettings(osgUtil::CullVisitor& cv, ViewDependentData* vdd);
-
         virtual void createShaders();
 
         virtual bool selectActiveLights(osgUtil::CullVisitor* cv, ViewDependentData* vdd) const;
@@ -255,8 +252,6 @@ namespace SceneUtil {
 
         virtual bool adjustPerspectiveShadowMapCameraSettings(osgUtil::RenderStage* renderStage, Frustum& frustum, LightData& positionedLight, osg::Camera* camera, double viewNear, double viewFar);
 
-        virtual bool assignTexGenSettings(osgUtil::CullVisitor* cv, osg::Camera* camera, unsigned int textureUnit, osg::TexGen* texgen);
-
         virtual void cullShadowReceivingScene(osgUtil::CullVisitor* cv) const;
 
         virtual void cullShadowCastingScene(osgUtil::CullVisitor* cv, osg::Camera* camera) const;

components/sceneutil/shadow.cpp

@@ -32,7 +32,7 @@ namespace SceneUtil
             = std::clamp(Settings::Manager::getInt("number of shadow maps", "Shadows"), 1, 8);
 
         mShadowSettings->setNumShadowMapsPerLight(numberOfShadowMapsPerLight);
-        mShadowSettings->setBaseShadowTextureUnit(8 - numberOfShadowMapsPerLight);
+        mShadowSettings->setBaseShadowTextureUnit(osg::GLExtensions::Get(0, false)->glMaxTextureUnits - numberOfShadowMapsPerLight);
 
         const float maximumShadowMapDistance = Settings::Manager::getFloat("maximum shadow map distance", "Shadows");
         if (maximumShadowMapDistance > 0)

files/shaders/shadows_vertex.glsl

@@ -2,6 +2,7 @@
 
 #if SHADOWS
     @foreach shadow_texture_unit_index @shadow_texture_unit_list
+        uniform mat4 shadowSpaceMatrix@shadow_texture_unit_index;
         uniform int shadowTextureUnit@shadow_texture_unit_index;
         varying vec4 shadowSpaceCoords@shadow_texture_unit_index;
 
@@ -19,33 +20,28 @@ void setupShadowCoords(vec4 viewPos, vec3 viewNormal)
 {
 #if SHADOWS
     // This matrix has the opposite handedness to the others used here, so multiplication must have the vector to the left. Alternatively it could be transposed after construction, but that's extra work for the GPU just to make the code look a tiny bit cleaner.
-    mat4 eyePlaneMat;
     vec4 shadowOffset;
     @foreach shadow_texture_unit_index @shadow_texture_unit_list
-        eyePlaneMat = mat4(gl_EyePlaneS[shadowTextureUnit@shadow_texture_unit_index], gl_EyePlaneT[shadowTextureUnit@shadow_texture_unit_index], gl_EyePlaneR[shadowTextureUnit@shadow_texture_unit_index], gl_EyePlaneQ[shadowTextureUnit@shadow_texture_unit_index]);
-
 #if @perspectiveShadowMaps
         shadowRegionCoords@shadow_texture_unit_index = validRegionMatrix@shadow_texture_unit_index * viewPos;
 #endif
 
 #if @disableNormalOffsetShadows
-        shadowSpaceCoords@shadow_texture_unit_index = viewPos * eyePlaneMat;
+        shadowSpaceCoords@shadow_texture_unit_index = shadowSpaceMatrix@shadow_texture_unit_index * viewPos;
 #else
         shadowOffset = vec4(viewNormal * @shadowNormalOffset, 0.0);
 
         if (onlyNormalOffsetUV)
         {
-            shadowSpaceCoords@shadow_texture_unit_index = viewPos * eyePlaneMat;
-
             vec4 lightSpaceXY = viewPos + shadowOffset;
-            lightSpaceXY = lightSpaceXY * eyePlaneMat;
+            lightSpaceXY = shadowSpaceMatrix@shadow_texture_unit_index * lightSpaceXY;
 
             shadowSpaceCoords@shadow_texture_unit_index.xy = lightSpaceXY.xy;
         }
         else
         {
             vec4 offsetViewPosition = viewPos + shadowOffset;
-            shadowSpaceCoords@shadow_texture_unit_index = offsetViewPosition * eyePlaneMat;
+            shadowSpaceCoords@shadow_texture_unit_index = shadowSpaceMatrix@shadow_texture_unit_index * offsetViewPosition;
         }
 #endif
     @endforeach