Pixel perfect volume shader

Now the volume should render with pixel perfect accuracy.
The drawback is that it is significantly slower than the old
approximate solution.

Change-Id: I4df7e9a28a27b56150c71a85a4c1fb69a215dabc
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/src/datavisualization/engine/abstract3drenderer.cpp b/src/datavisualization/engine/abstract3drenderer.cpp
index 090a833a..78f4b600 100644
--- a/src/datavisualization/engine/abstract3drenderer.cpp
+++ b/src/datavisualization/engine/abstract3drenderer.cpp
@@ -1320,15 +1320,15 @@ void Abstract3DRenderer::drawCustomItems(RenderingState state,
                     } else {
                         // Precalculate texture dimensions so we can optimize
                         // ray stepping to hit every texture layer.
-                        QVector3D textureDimensions(float(item->textureWidth()),
-                                                    float(item->textureHeight()),
-                                                    float(item->textureDepth()));
+                        QVector3D textureDimensions(1.0f / float(item->textureWidth()),
+                                                    1.0f / float(item->textureHeight()),
+                                                    1.0f / float(item->textureDepth()));
                         shader->setUniformValue(shader->textureDimensions(), textureDimensions);
 
-                        int sampleCount = qMax(item->textureWidth(), item->textureHeight());
-                        sampleCount = qMax(sampleCount, item->textureDepth());
+                        // Worst case scenario sample count
+                        int sampleCount = item->textureWidth() + item->textureHeight()
+                                + item->textureDepth();
                         shader->setUniformValue(shader->sampleCount(), sampleCount);
-
                     }
                     m_drawer->drawObject(shader, item->mesh(), 0, 0, item->texture());
                 } else