diff --git a/base/vulkantools.cpp b/base/vulkantools.cpp
index 46669d53..eafb999f 100644
--- a/base/vulkantools.cpp
+++ b/base/vulkantools.cpp
@@ -126,81 +126,94 @@ namespace vkTools
 		imageMemoryBarrier.subresourceRange = subresourceRange;
 
 		// Source layouts (old)
-
-		// Undefined layout
-		// Only allowed as initial layout!
-		// Make sure any writes to the image have been finished
-		if (oldImageLayout == VK_IMAGE_LAYOUT_PREINITIALIZED)
+		// Source access mask controls actions that have to be finished on the old layout
+		// before it will be transitioned to the new layout
+		switch (oldImageLayout)
 		{
-			imageMemoryBarrier.srcAccessMask = VK_ACCESS_HOST_WRITE_BIT | VK_ACCESS_TRANSFER_WRITE_BIT;
-		}
+		case VK_IMAGE_LAYOUT_UNDEFINED:
+				// Image layout is undefined (or does not matter)
+				// Only valid as initial layout
+				// No flags required, listed only for completeness
+				imageMemoryBarrier.srcAccessMask = 0;
+				break;
 
-		// Old layout is color attachment
-		// Make sure any writes to the color buffer have been finished
-		if (oldImageLayout == VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL) 
-		{
-			imageMemoryBarrier.srcAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
-		}
+		case VK_IMAGE_LAYOUT_PREINITIALIZED:
+				// Image is preinitialized
+				// Only valid as initial layout for linear images, preserves memory contents
+				// Make sure host writes have been finished
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_HOST_WRITE_BIT;
+				break;
 
-		// Old layout is depth/stencil attachment
-		// Make sure any writes to the depth/stencil buffer have been finished
-		if (oldImageLayout == VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL)
-		{
-			imageMemoryBarrier.srcAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT;
-		}
+		case VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL:
+				// Image is a color attachment
+				// Make sure any writes to the color buffer have been finished
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+				break;
 
-		// Old layout is transfer source
-		// Make sure any reads from the image have been finished
-		if (oldImageLayout == VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL)
-		{
-			imageMemoryBarrier.srcAccessMask = VK_ACCESS_TRANSFER_READ_BIT;
-		}
+		case VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL:
+				// Image is a depth/stencil attachment
+				// Make sure any writes to the depth/stencil buffer have been finished
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT;
+				break;
 
-		// Old layout is shader read (sampler, input attachment)
-		// Make sure any shader reads from the image have been finished
-		if (oldImageLayout == VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL)
-		{
-			imageMemoryBarrier.srcAccessMask = VK_ACCESS_SHADER_READ_BIT;
+		case VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL:
+				// Image is a transfer source 
+				// Make sure any reads from the image have been finished
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_TRANSFER_READ_BIT;
+				break;
+
+		case VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL:
+				// Image is a transfer destination
+				// Make sure any writes to the image have been finished
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_TRANSFER_WRITE_BIT;
+				break;
+
+		case VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL:
+				// Image is read by a shader
+				// Make sure any shader reads from the image have been finished
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_SHADER_READ_BIT;
+				break;
 		}
 
 		// Target layouts (new)
-
-		// New layout is transfer destination (copy, blit)
-		// Make sure any copyies to the image have been finished
-		if (newImageLayout == VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL)
+		// Destination access mask controls the dependency for the new image layout
+		switch (newImageLayout)
 		{
+		case VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL:
+			// Image will be used as a transfer destination
+			// Make sure any writes to the image have been finished
 			imageMemoryBarrier.dstAccessMask = VK_ACCESS_TRANSFER_WRITE_BIT;
-		}
+			break;
 
-		// New layout is transfer source (copy, blit)
-		// Make sure any reads from and writes to the image have been finished
-		if (newImageLayout == VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL)
-		{
+		case VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL:
+			// Image will be used as a transfer source
+			// Make sure any reads from and writes to the image have been finished
 			imageMemoryBarrier.srcAccessMask = imageMemoryBarrier.srcAccessMask | VK_ACCESS_TRANSFER_READ_BIT;
 			imageMemoryBarrier.dstAccessMask = VK_ACCESS_TRANSFER_READ_BIT;
-		}
+			break;
 
-		// New layout is color attachment
-		// Make sure any writes to the color buffer hav been finished
-		if (newImageLayout == VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL)
-		{
-			imageMemoryBarrier.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+		case VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL:
+			// Image will be used as a color attachment
+			// Make sure any writes to the color buffer have been finished
 			imageMemoryBarrier.srcAccessMask = VK_ACCESS_TRANSFER_READ_BIT;
-		}
+			imageMemoryBarrier.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+			break;
 
-		// New layout is depth attachment
-		// Make sure any writes to depth/stencil buffer have been finished
-		if (newImageLayout == VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL) 
-		{
+		case VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL:
+			// Image layout will be used as a depth/stencil attachment
+			// Make sure any writes to depth/stencil buffer have been finished
 			imageMemoryBarrier.dstAccessMask = imageMemoryBarrier.dstAccessMask | VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT;
-		}
+			break;
 
-		// New layout is shader read (sampler, input attachment)
-		// Make sure any writes to the image have been finished
-		if (newImageLayout == VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL)
-		{
-			imageMemoryBarrier.srcAccessMask = VK_ACCESS_HOST_WRITE_BIT | VK_ACCESS_TRANSFER_WRITE_BIT;
+		case VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL:
+			// Image will be read in a shader (sampler, input attachment)
+			// Make sure any writes to the image have been finished
+			if (imageMemoryBarrier.srcAccessMask == 0)
+			{
+				imageMemoryBarrier.srcAccessMask = VK_ACCESS_HOST_WRITE_BIT | VK_ACCESS_TRANSFER_WRITE_BIT;
+			}
 			imageMemoryBarrier.dstAccessMask = VK_ACCESS_SHADER_READ_BIT;
+			break;
 		}
 
 		// Put barrier on top