Switch from back face culling to back face culling so that the rays s…

…tart at the back of the brick and march forwards towards the eye through the volume

examples/volume/vsgvolume/vsgvolume.cpp

@@ -214,8 +214,8 @@ int main(int argc, char** argv)
     auto vertexShader = vsg::read_cast<vsg::ShaderStage>("shaders/volume.vert", options);
     auto fragmentShader = vsg::read_cast<vsg::ShaderStage>("shaders/volume.frag", options);
 
-    // if (!vertexShader) vertexShader = vsg::ShaderStage::create(VK_SHADER_STAGE_VERTEX_BIT, "main", volume_vert);
-    // if (!fragmentShader) fragmentShader = vsg::ShaderStage::create(VK_SHADER_STAGE_FRAGMENT_BIT, "main", volume_frag);
+    if (!vertexShader) vertexShader = vsg::ShaderStage::create(VK_SHADER_STAGE_VERTEX_BIT, "main", volume_vert);
+    if (!fragmentShader) fragmentShader = vsg::ShaderStage::create(VK_SHADER_STAGE_FRAGMENT_BIT, "main", volume_frag);
 
     if (!vertexShader || !fragmentShader)
     {
@@ -254,10 +254,14 @@ int main(int argc, char** argv)
         VkVertexInputAttributeDescription{0, 0, VK_FORMAT_R32G32B32_SFLOAT, 0}, // vertex data
     };
 
+
+    auto rasterizationState = vsg::RasterizationState::create();
+    rasterizationState->cullMode = VK_CULL_MODE_FRONT_BIT;
+
     vsg::GraphicsPipelineStates pipelineStates{
         vsg::VertexInputState::create(vertexBindingsDescriptions, vertexAttributeDescriptions),
         vsg::InputAssemblyState::create(),
-        vsg::RasterizationState::create(),
+        rasterizationState,
         vsg::MultisampleState::create(),
         vsg::ColorBlendState::create(),
         vsg::DepthStencilState::create()};