Advanced Raycasting features

* ambient occlusion refactored as a decorator
* pre-integrated raycaster and processor to pre-integrate TF

modules/advancedraycasting/advancedraycasting.cmake

@@ -4,7 +4,8 @@ SET(ThisModStatus EXPERIMENTAL)
 
 IF(${ModuleEnabled})
 	# Source files:
-	FILE(GLOB ThisModSources RELATIVE ${ModulesDir}
+    FILE(GLOB ThisModSources RELATIVE ${ModulesDir}
+        modules/advancedraycasting/decorators/*.cpp
 		modules/advancedraycasting/pipelines/*.cpp
 		modules/advancedraycasting/processors/*.cpp
 		modules/advancedraycasting/tools/*.cpp
@@ -17,7 +18,8 @@ IF(${ModuleEnabled})
 		modules/advancedraycasting/glsl/*.geom
         modules/advancedraycasting/glsl/*.vert
         modules/advancedraycasting/glsl/*.comp
-		modules/advancedraycasting/pipelines/*.h
+        modules/advancedraycasting/decorators/*.h
+        modules/advancedraycasting/pipelines/*.h
 		modules/advancedraycasting/processors/*.h
 		modules/advancedraycasting/tools/*.h
 	)

modules/advancedraycasting/advancedraycasting.cpp

@@ -25,13 +25,21 @@
 #include "core/pipeline/pipelinefactory.h"
 #include "core/pipeline/processorfactory.h"
 
+#include "modules/advancedraycasting/pipelines/preintegratedraycasterdemo.h"
+
+#include "modules/advancedraycasting/processors/ambientvolumegenerator.h"
 #include "modules/advancedraycasting/processors/laoraycaster.h"
+#include "modules/advancedraycasting/processors/preintegratedraycaster.h"
+#include "modules/advancedraycasting/processors/tfpreintegrator.h"
 
 namespace campvis {
 
     // explicitly instantiate templates to register the pipelines
-    //template class PipelineRegistrar<OCTStereoPlaneDemo>;
+    template class PipelineRegistrar<PreintegratedRayCasterDemo>;
 
+    template class SmartProcessorRegistrar<AmbientVolumeGenerator>;
     template class SmartProcessorRegistrar<LAORaycaster>;
+    template class SmartProcessorRegistrar<PreintegratedRaycaster>;
+    template class SmartProcessorRegistrar<TFPreIntegrator>;
 
 }

modules/advancedraycasting/decorators/localambientocclusiondecorator.cpp

+// ================================================================================================
+// 
+// This file is part of the CAMPVis Software Framework.
+// 
+// If not explicitly stated otherwise: Copyright (C) 2012-2015, all rights reserved,
+//      Christian Schulte zu Berge <christian.szb@in.tum.de>
+//      Chair for Computer Aided Medical Procedures
+//      Technische Universitaet Muenchen
+//      Boltzmannstr. 3, 85748 Garching b. Muenchen, Germany
+// 
+// For a full list of authors and contributors, please refer to the file "AUTHORS.txt".
+// 
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file 
+// except in compliance with the License. You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software distributed under the 
+// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
+// either express or implied. See the License for the specific language governing permissions 
+// and limitations under the License.
+// 
+// ================================================================================================
+
+#include "localambientocclusiondecorator.h"
+
+#include "cgt/shadermanager.h"
+#include "cgt/textureunit.h"
+#include "core/properties/propertycollection.h"
+
+#include "core/datastructures/imagerepresentationgl.h"
+#include "core/datastructures/renderdata.h"
+#include "core/classification/geometry1dtransferfunction.h"
+
+namespace campvis {
+
+    LocalAmbientOcclusionDecorator::LocalAmbientOcclusionDecorator()
+        : AbstractProcessorDecorator()
+        , p_aoRays("AORays", "Number of directional samples", 8, 0, 50)
+        , p_aoSamples("AOSamples", "Number of Samples per ray (controls size of AO sphere)", 10, 0, 80)
+        , p_aoSphereRadius("AOSphereRadius", "AO Sphere Radius [voxels]", 8.0f, 0.1f, 50.0f, 0.25f)
+        , p_aoOpacityScale("OpacityScale", "Opacity Scaling", 1.0f, 0.0f, 5.f)
+        , p_aoEffectGamma("AOEffectGamma", "AO Scale Gamma", 1.0f, .0f, 5.f)
+        , p_aoEmissiveTransferFunction("AOTransferFunction", "Emissive Transfer Function", new Geometry1DTransferFunction(128))
+        , p_aoEmissiveScale("EmissiveScale", "Emissive Color Scaling", 1.0f, 0.0f, 10.f)
+    {
+    }
+
+    LocalAmbientOcclusionDecorator::~LocalAmbientOcclusionDecorator() {
+
+    }
+
+    void LocalAmbientOcclusionDecorator::addProperties(AbstractProcessor* propCollection) {
+        propCollection->addProperty(p_aoRays, AbstractProcessor::INVALID_RESULT | AbstractProcessor::INVALID_PROPERTIES | AbstractProcessor::INVALID_SHADER);
+        propCollection->addProperty(p_aoSamples, AbstractProcessor::INVALID_RESULT | AbstractProcessor::INVALID_PROPERTIES | AbstractProcessor::INVALID_SHADER);
+        propCollection->addProperty(p_aoSphereRadius);
+        propCollection->addProperty(p_aoOpacityScale);
+        propCollection->addProperty(p_aoEffectGamma);
+        propCollection->addProperty(p_aoEmissiveTransferFunction);
+        propCollection->addProperty(p_aoEmissiveScale);
+    }
+
+    void LocalAmbientOcclusionDecorator::renderProlog(const DataContainer& dataContainer, cgt::Shader* shader) {
+        auto aotf = p_aoEmissiveTransferFunction.getTF();
+        _aoTFUnit = std::make_unique<cgt::TextureUnit>();
+        aotf->bind(shader, *_aoTFUnit, "_aoEmissiveTF", "_aoEmissiveTFParams");
+
+        shader->setUniform("_aoSphereRadius", p_aoSphereRadius.getValue());
+        shader->setUniform("_aoGamma", p_aoEffectGamma.getValue());
+        shader->setUniform("_aoEmissiveScale", p_aoEmissiveScale.getValue());
+        shader->setUniform("_aoOpacityScale", p_aoOpacityScale.getValue());
+    }
+
+    void LocalAmbientOcclusionDecorator::renderEpilog(cgt::Shader * shader)
+    {
+        // delete the TF texture unit
+        _aoTFUnit = nullptr;
+    }
+
+    std::string LocalAmbientOcclusionDecorator::generateHeader() const
+    {
+        std::string toReturn;
+        // the defines need to exist before the include
+        toReturn +=
+            "#define NUM_AO_RAYS " + std::to_string(p_aoRays.getValue()) + "\n"
+            "#define NUM_AO_RAY_STEPS " + std::to_string(p_aoSamples.getValue()) + "\n"
+            "\n"
+            "uniform float _aoSphereRadius;\n"
+            "uniform float _aoGamma;\n"
+            "uniform float _aoOpacityScale;\n"
+            "uniform float _aoEmissiveScale;\n"
+            "\n"
+            "#define AO_GAMMA _aoGamma\n"
+            "#define AO_OPACITY_SCALE _aoOpacityScale\n"
+            "#define AO_EMISSIVE_SCALE _aoEmissiveScale\n";
+
+        // the include has the actual functions
+        toReturn += "#include \"modules/advancedraycasting/glsl/localambientocclusion.frag\"\n";
+
+        return toReturn;
+    }
+
+}

modules/advancedraycasting/decorators/localambientocclusiondecorator.h

+// ================================================================================================
+// 
+// This file is part of the CAMPVis Software Framework.
+// 
+// If not explicitly stated otherwise: Copyright (C) 2012-2015, all rights reserved,
+//      Christian Schulte zu Berge <christian.szb@in.tum.de>
+//      Chair for Computer Aided Medical Procedures
+//      Technische Universitaet Muenchen
+//      Boltzmannstr. 3, 85748 Garching b. Muenchen, Germany
+// 
+// For a full list of authors and contributors, please refer to the file "AUTHORS.txt".
+// 
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file 
+// except in compliance with the License. You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software distributed under the 
+// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
+// either express or implied. See the License for the specific language governing permissions 
+// and limitations under the License.
+// 
+// ================================================================================================
+
+#ifndef LOCALAMBIENTOCCLUSIONDECORATOR_H__
+#define LOCALAMBIENTOCCLUSIONDECORATOR_H__
+
+#include "core/pipeline/abstractprocessordecorator.h"
+#include "core/properties/floatingpointproperty.h"
+#include "core/properties/datanameproperty.h"
+#include "core/properties/colorproperty.h"
+#include "core/properties/optionproperty.h"
+#include "core/properties/transferfunctionproperty.h"
+
+#include "modules/modulesapi.h"
+
+namespace cgt {
+    class TextureUnit;
+}
+
+namespace campvis {
+    /**
+     *  \class RaycastingGridDecorator
+     *  Provides a fragment shader function that can test samples and modify their opacity valued to 
+     */
+    class CAMPVIS_MODULES_API LocalAmbientOcclusionDecorator : public AbstractProcessorDecorator {
+    public:
+        LocalAmbientOcclusionDecorator();
+        virtual ~LocalAmbientOcclusionDecorator();
+
+    protected:
+        void addProperties(AbstractProcessor* propCollection) override;
+
+        virtual void renderProlog(const DataContainer& dataContainer, cgt::Shader* shader) override;
+
+        virtual void renderEpilog(cgt::Shader* shader) override;
+
+        virtual std::string generateHeader() const override;
+
+        IntProperty  p_aoRays;                      ///< Number of directional AO samples
+        IntProperty  p_aoSamples;                   ///< Number of steps per directional sample
+        FloatProperty p_aoSphereRadius;             ///< The AO Sphere radius in voxels
+        FloatProperty p_aoEffectGamma;              ///< Gamma controls the strength of the AO effect
+        FloatProperty p_aoOpacityScale;             ///< Scales opacity when sampling for AO rays
+
+        TransferFunctionProperty p_aoEmissiveTransferFunction;
+        FloatProperty p_aoEmissiveScale;            ///< Scales the emissive color to increase/decrease the emissive effect
+
+        std::unique_ptr<cgt::TextureUnit> _aoTFUnit;
+    };
+
+}
+
+#endif // LOCALAMBIENTOCCLUSIONDECORATOR_H__

modules/advancedraycasting/glsl/ambientvolumegenerator.comp

+// ================================================================================================
+// 
+// This file is part of the CAMPVis Software Framework.
+// 
+// If not explicitly stated otherwise: Copyright (C) 2012-2015, all rights reserved,
+//      Christian Schulte zu Berge <christian.szb@in.tum.de>
+//      Chair for Computer Aided Medical Procedures
+//      Technische Universitaet Muenchen
+//      Boltzmannstr. 3, 85748 Garching b. Muenchen, Germany
+// 
+// For a full list of authors and contributors, please refer to the file "AUTHORS.txt".
+// 
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file 
+// except in compliance with the License. You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software distributed under the 
+// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
+// either express or implied. See the License for the specific language governing permissions 
+// and limitations under the License.
+// 
+// ================================================================================================
+
+// (c) 2017 Jakob Weiss <jakob.weiss@tum.de>
+
+// ==================== Shader for median filtering. ====================
+// Expects the following dynamic defines:
+//
+// #define OUTPUT_TEXTURE_FORMAT
+//          The texture format of the output texture. Preferrably specified through Texture::calcMatchingWriteFormat()
+//
+// uniform _outputImage
+//          dynamically defined (i|u)image(1|2|3)D uniform to allow imageStore operation of the output
+// #define TEXTURE_DIMENSIONALITY
+//          The dimensionality of the texture [1,2,3]
+
+// The work group size can be overridden by dynamic defines
+#ifndef WORK_GROUP_SIZE_X
+#define WORK_GROUP_SIZE_X 1
+#endif
+#ifndef WORK_GROUP_SIZE_Y
+#define WORK_GROUP_SIZE_Y 1
+#endif
+#ifndef WORK_GROUP_SIZE_Z
+#define WORK_GROUP_SIZE_Z 1
+#endif
+
+#include "tools/transferfunction.frag"
+
+
+// volume
+uniform sampler3D _volume;
+uniform TextureParameters3D _volumeTextureParams;
+
+// Transfer function
+uniform sampler1D _transferFunction;
+uniform TFParameters1D _transferFunctionParams;
+
+// Transfer function
+uniform sampler1D _aoEmissiveTF;
+uniform TFParameters1D _aoEmissiveTFParams;
+
+layout(local_size_x = WORK_GROUP_SIZE_X, local_size_y = WORK_GROUP_SIZE_Y, local_size_z = WORK_GROUP_SIZE_Z) in;
+
+
+void main() {
+    // get index in global work group i.e x,y position
+    ivec3 pixel_coords = ivec3(gl_GlobalInvocationID.xyz);
+    vec3 samplePosition = vec3(pixel_coords)*_volumeTextureParams._sizeRCP;
+
+    float sampleIntensity = texture(_volume, samplePosition).r;
+    vec4 sampleTFColor = lookupTF(_transferFunction, _transferFunctionParams, sampleIntensity);
+    
+    // precompute the LAO ray directions
+    vec4 aoRayDirs[NUM_AO_RAYS];
+    initLAODirs(aoRayDirs, _aoSphereRadius, _volumeTextureParams);
+
+    vec3 ambientOcclusion = computeLAO(samplePosition, aoRayDirs, _volume, _transferFunction, _transferFunctionParams, _aoEmissiveTF, _aoEmissiveTFParams);
+
+    vec4 result = vec4(ambientOcclusion, sampleTFColor.a);
+
+    // output to a specific pixel in the image
+    #if TEXTURE_DIMENSIONALITY == 1
+    imageStore(_outputImage, pixel_coords.x, vec4(result));
+    #elif TEXTURE_DIMENSIONALITY == 2
+    imageStore(_outputImage, pixel_coords.xy, vec4(result));
+    #else
+    imageStore(_outputImage, pixel_coords, vec4(result));
+    #endif
+
+}

modules/advancedraycasting/glsl/genericraycastingloop.frag

+
+
+// (c) 2017 Jakob Weiss
+
+/**
+ ** Prerequisites: **
+
+  - _samplingStepSize
+  - _jitterStepSizeMultiplier
+  - _lightSource
+
+  - vec4 getSampleColor(vec3 sampleTexPos)
+  - float getSampleAlpha(vec3 sampleTexPos)
+  - vec3 getSampleGradient(vec3 sampleTexPos)
+  
+  If ENABLE_SHADOWING is set:
+  - _lightSource
+  - _shadowIntensity
+
+  If ENABLE_SHADING is set:
+  - _lightSource
+  - _cameraPosition
+
+ */
+
+/**
+ * Performs the raycasting and returns the final fragment color.
+ */
+vec4 performRaycasting(in vec3 entryPoint, in vec3 exitPoint, in vec2 texCoords) {
+    vec4 result = vec4(0.0);
+    float firstHitT = -1.0;
+
+    // calculate ray parameters
+    vec3 direction = exitPoint.rgb - entryPoint.rgb;
+    float t = 0.0;
+    float tend = length(direction);
+    direction = normalize(direction);
+
+    jitterEntryPoint(entryPoint, direction, _samplingStepSize * _jitterStepSizeMultiplier);
+
+#ifdef ENABLE_SHADOWING
+    vec3 lightSourcePositionInTex = worldToTexture(_volumeTextureParams, _lightSource._position);
+#endif
+
+    while (t < tend) {
+        // compute sample position
+        vec3 samplePosition = entryPoint.rgb + t * direction;
+
+        // lookup intensity and TF
+        vec4 color = getSampleColor(samplePosition);
+
+#ifdef ENABLE_SHADOWING
+        float shadowSamplingStepSize = 2 * _samplingStepSize;
+        // compute direction from sample to light
+        vec3 L = normalize(lightSourcePositionInTex - samplePosition) * shadowSamplingStepSize;
+
+        // simple and expensive implementation of hard shadows
+        if (color.a > 0.01) {
+            bool finished = false;
+
+            vec3 shadowSamplePosition = samplePosition + L;
+            jitterEntryPoint(shadowSamplePosition, L, _jitterStepSizeMultiplier);
+
+            int lightSamples = SHADOW_STEPS;
+
+            float shadowFactor = 0.0;
+
+            // traverse ray from sample to light
+            while (! finished) {
+                // grab transparency for the shadow sample
+                shadowFactor += getSampleAlpha(shadowSamplePosition);
+
+                shadowSamplePosition += L;
+                finished = //(shadowFactor > 0.95)
+                        --lightSamples < 0
+                         || any(lessThan(shadowSamplePosition, vec3(0.0, 0.0, 0.0)))
+                         || any(greaterThan(shadowSamplePosition, vec3(1.0, 1.0, 1.0)));
+            }
+            // apply shadow to color
+            color.rgb *= exp(- shadowFactor * shadowSamplingStepSize * _shadowIntensity * SAMPLING_BASE_INTERVAL_RCP);
+        }
+#endif // ENABLE_SHADOWS
+
+        // perform compositing
+        if (color.a > 0.0) {
+#ifdef ENABLE_SHADING
+            // compute gradient (needed for shading and normals)
+            vec3 gradient = getSampleGradient(samplePosition);
+            vec4 worldPos = _volumeTextureParams._textureToWorldMatrix * vec4(samplePosition, 1.0); // calling textureToWorld here crashes Intel HD driver and nVidia driver in debug mode, hence, let's calc it manually...
+            vec3 normal = -normalize(vec4(gradient, 0.0)).xyz; // negated because gradient is along increasing intensity but we want a surface normal
+            color.rgb = calculatePhongShading(worldPos.xyz / worldPos.w, _lightSource, _cameraPosition, normal, color.rgb);
+#endif
+
+            // accomodate for variable sampling rates
+            color.a = 1.0 - pow(1.0 - color.a, _samplingStepSize * SAMPLING_BASE_INTERVAL_RCP);
+            blendUnder(result, color);
+        }
+
+        // save first hit ray parameter for depth value calculation
+        if (firstHitT < 0.0 && result.a > 0.3) {
+            firstHitT = t;
+            out_FHP = vec4(samplePosition, 1.0);
+            out_FHN = vec4(-normalize(getSampleGradient(samplePosition)), 1.0);
+        }
+
+        // early ray termination
+        if (result.a > 0.975) {
+            result.a = 1.0;
+            t = tend;
+        }
+
+        // advance to the next evaluation point along the ray
+        t += _samplingStepSize;
+    }
+
+    // calculate depth value from ray parameter
+    gl_FragDepth = 1.0;
+    if (firstHitT >= 0.0) {
+        float depthEntry = texture(_entryPointsDepth, texCoords).z;
+        float depthExit = texture(_exitPointsDepth, texCoords).z;
+        gl_FragDepth = calculateDepthValue(firstHitT/tend, depthEntry, depthExit);
+    }
+    return result;
+}

modules/advancedraycasting/glsl/laoraycaster.frag

@@ -34,17 +34,6 @@ layout(location = 2) out vec4 out_FHN;       ///< outgoing fragment first hit no
 #include "tools/transferfunction.frag"
 
 
-uniform float _aoSphereRadius;
-uniform float _aoGamma;
-uniform float _aoOpacityScale;
-uniform float _aoEmissiveScale;
-
-#define AO_GAMMA _aoGamma
-#define AO_OPACITY_SCALE _aoOpacityScale
-#define AO_EMISSIVE_SCALE _aoEmissiveScale
-
-#include "../../modules/advancedraycasting/glsl/localambientocclusion.frag"
-
 uniform vec2 _viewportSizeRCP;
 uniform float _jitterStepSizeMultiplier;
 
@@ -78,6 +67,7 @@ uniform float _samplingStepSize;
 
 const float SAMPLING_BASE_INTERVAL_RCP = 200.0;
 
+//#define DEBUG_AO_DIRECTIONS
 
 /**
  * Performs the raycasting and returns the final fragment color.
@@ -106,10 +96,39 @@ vec4 performRaycasting(in vec3 entryPoint, in vec3 exitPoint, in vec2 texCoords)
         float intensity = texture(_volume, samplePosition).r;
         vec4 color = lookupTF(_transferFunction, _transferFunctionParams, intensity);
 
+#ifdef DEBUG_AO_DIRECTIONS
+       // allows to quickly check if the ray directions are uniformly distributed even for non-uniform volume/voxel sizes
+        color = vec4(0);
+        for(int i=0; i < NUM_AO_RAYS; ++i) {
+            //vec3 dir = nthSphereSample(1.0, i, NUM_AO_RAYS);
+            vec4 dir = aoRayDirs[i];
+            vec3 p = samplePosition - vec3(0.5);// + dir.xyz*200;
+            float d = 1. - clamp(dot(normalize(p), normalize(dir.xyz)), 0, 1);
+            float r = length(p) - 10*length(dir.xyz);
+            //r *= smoothstep(0.4, 0.5, length(p));
+            float a= clamp(exp(-d*d/0.01) * exp(-r*r/0.001), 0, 1);
+
+            if(r > 0 && color.a < a) {
+                color.rgb = abs(normalize(dir.xyz));
+                color.a = a;
+            }
+        }
+
+        // accomodate for variable sampling rates
+        color.a = 1.0 - pow(1.0 - color.a, _samplingStepSize * SAMPLING_BASE_INTERVAL_RCP);
+        blendUnder(result, color);
+
+#else
+
         // perform compositing
         if (color.a > 0.0) {
             vec3 n;
             vec3 ambientOcclusion = computeLAO(samplePosition, aoRayDirs, _volume, _transferFunction, _transferFunctionParams, _aoEmissiveTF, _aoEmissiveTFParams, n);
+            vec4 aoSampleColor = lookupTF(_aoEmissiveTF, _aoEmissiveTFParams, intensity);
+            // emissive transfer function overrides the original TF color
+            if(aoSampleColor.a > 0) {
+                color.rgb = aoSampleColor.rgb;
+            }
 
 #ifdef ENABLE_SHADING
             // compute gradient (needed for shading and normals)
@@ -119,15 +138,19 @@ vec4 performRaycasting(in vec3 entryPoint, in vec3 exitPoint, in vec2 texCoords)
             vec3 normal = -normalize(_volumeTextureParams._textureToWorldMatrixInvTransp * vec4(n, 0.0)).xyz; // negated because gradient is along increasing intensity but we want a surface normal
             color.rgb = calculatePhongShading(worldPos.xyz / worldPos.w, ambientOcclusion, _lightSource, _cameraPosition, normal, color.rgb);
 #else
-            color.rgb *= ambientOcclusion;
+            color.rgb *= ambientOcclusion;//*normalize(abs(n));
 #endif
 
-
+// With this enabled, raycaster will show the influence of the AO comptuation. useful for parameter tuning and debugging
+#ifdef SHOW_AO_ONLY
+            color.rgb = ambientOcclusion;
+#endif
 
             // accomodate for variable sampling rates
             color.a = 1.0 - pow(1.0 - color.a, _samplingStepSize * SAMPLING_BASE_INTERVAL_RCP);
             blendUnder(result, color);
         }
+#endif
 
         // save first hit ray parameter for depth value calculation
         if (firstHitT < 0.0 && result.a > 0.0) {

modules/advancedraycasting/glsl/localambientocclusion.frag

@@ -25,6 +25,7 @@
 // (c) 2017 Jakob Weiss <jakob.weiss@tum.de>
 
 #include "tools/transferfunction.frag"
+#include "tools/texture3d.frag"
 
 // The number of rays in each direction
 #ifndef NUM_AO_RAYS
@@ -77,16 +78,12 @@ vec4 computeLAORay(vec3 pos, vec3 dir, float aoStepSize, sampler3D tex, sampler1
         float aoSampleOpacity = aoSampleColor.a * AO_OPACITY_SCALE; // Volume tf sample is used for it's opacity value
         vec4 aoSampleEmissive = lookupTF(aoEmissiveTF, aoEmissiveTFParams, aoIntensity); // AO sample is used for the material's emissive color
 
-        //testing
-        aoSampleEmissive.rgb = aoSampleColor.rgb*aoSampleEmissive.a;
-
         // compensate step size
         aoSampleOpacity = 1.0 - pow(1.0 - aoSampleOpacity, AO_GAMMA * aoStepSize * AO_SAMPLING_BASE_INTERVAL_RCP);
-        //aoSampleEmissive.rgb *= aoStepSize * AO_SAMPLING_BASE_INTERVAL_RCP  * aoSampleEmissive.a; // ao emissive color is multiplied by alpha for controlling the intensity
+        aoSampleEmissive.rgb *= aoStepSize * AO_SAMPLING_BASE_INTERVAL_RCP  * aoSampleEmissive.a; // ao emissive color is multiplied by alpha for controlling the intensity
 
-        // accumulate 
+        // accumulate
         aoColor.rgb += (vec3(1) + AO_EMISSIVE_SCALE * aoSampleEmissive.rgb) * aoColor.a;
-
         aoColor.a *= (1 - aoSampleOpacity);
 
         aoRayPos += aoStep;
@@ -95,13 +92,22 @@ vec4 computeLAORay(vec3 pos, vec3 dir, float aoStepSize, sampler3D tex, sampler1
     return aoColor;
 }
 
-void initLAODirs(inout vec4 aoRayDirs[NUM_AO_RAYS], float aoSphereRadius, TextureParameters3D volumeParameters) {
+void initLAODirs(inout vec4 aoRayDirs[NUM_AO_RAYS], float aoSphereRadius, TextureParameters3D volumeParameters)
+{
     //Normalize for anisotropic voxel sizes
-    vec3 anisotropicVoxel = volumeParameters._sizeRCP;// * volumeParameters._voxelSizeRCP;
+    vec3 anisotropicVoxel = volumeParameters._sizeRCP * volumeParameters._voxelSizeRCP;
     vec3 anisotropicRayStep = anisotropicVoxel / NUM_AO_RAY_STEPS;
+    float voxelSize = length(volumeParameters._sizeRCP) / sqrt(3);
+    float scale = aoSphereRadius * voxelSize / NUM_AO_RAY_STEPS;
+
     for(int i=0; i < NUM_AO_RAYS; ++i) {
-        aoRayDirs[i].rgb = anisotropicRayStep * nthSphereSample(aoSphereRadius, i, NUM_AO_RAYS);
-        aoRayDirs[i].a = length(aoRayDirs[i].rgb);
+        vec4 dir = vec4( nthSphereSample(1.0, i, NUM_AO_RAYS), 0.0);
+        aoRayDirs[i].xyz = scale * normalize((volumeParameters._worldToTextureMatrixInvTransp * dir).xyz);
+
+        //this is somehow slower to compute...
+        //aoRayDirs[i].xyz = anisotropicRayStep * nthSphereSample(aoSphereRadius, i, NUM_AO_RAYS);
+
+        aoRayDirs[i].w = length(aoRayDirs[i].xyz);
     }
 }
 
@@ -114,10 +120,10 @@ vec3 computeLAO(vec3 position, in vec4 aoRayDirs[NUM_AO_RAYS], sampler3D tex, sa
         for(int i=0; i < NUM_AO_RAYS; ++i) {
             //vec3 dir = nthSphereSample(1.0, i, NUM_AO_RAYS);
             vec4 dir = aoRayDirs[i];
-            vec4 aoRayColor = computeLAORay(position, dir.rgb, dir.a, tex, volumeTF, volumeTFParams, aoEmissiveTF, aoEmissiveTFParams);
+            vec4 aoRayColor = computeLAORay(position, dir.xyz, dir.w, tex, volumeTF, volumeTFParams, aoEmissiveTF, aoEmissiveTFParams);
             ambient += aoRayColor.rgb;
 
-            minOcclusionDir += (1.- aoRayColor.a) * dir.rgb;