generating of mipmaps using vkCmdBlitImage for cubemap textures - vulkan

Question

what should be the parameters of VkImageBlit.dstOffsets and VkImageBlit.srcOffsets when we are doing dynamic generation of mipmaps?
I am doing layer by layer and for each mipmap level but somewhere it is going wrong, mostly i think offsets. So i have data which has all the six faces with 0th mipmap level.
for(int j=0; j< bufferCopyRegions.size(); j++) {
for (int32_t i = 1; i < mipLevels; i++)
{
VkImageBlit imageBlit{};
// Source
imageBlit.srcSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
imageBlit.srcSubresource.layerCount = 1;
imageBlit.srcSubresource.mipLevel = 0;
imageBlit.srcOffsets[1].x = bitmapInfos[j].width;
imageBlit.srcOffsets[1].y = bitmapInfos[j].height;
imageBlit.srcOffsets[1].z = 1;
// Destination
imageBlit.dstSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
imageBlit.dstSubresource.layerCount = 1;
imageBlit.dstSubresource.mipLevel = i;
imageBlit.dstOffsets[1].x = int32_t(bitmapInfos[j].width >> (i) == 0 ? 1 : int32_t(bitmapInfos[j].width >> (i )));
imageBlit.dstOffsets[1].y = int32_t(bitmapInfos[j].height >> (i) == 0 ? 1 : int32_t(bitmapInfos[j].height >> (i)));
imageBlit.dstOffsets[1].z = 1;
VkImageMemoryBarrier imageMemoryBarrier = {};
imageMemoryBarrier.sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER;
imageMemoryBarrier.pNext = NULL;
imageMemoryBarrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
imageMemoryBarrier.subresourceRange.baseMipLevel = i;
imageMemoryBarrier.subresourceRange.levelCount = 1;
imageMemoryBarrier.subresourceRange.baseArrayLayer = j;
imageMemoryBarrier.subresourceRange.layerCount = 1;
// change layout of current mip level to transfer dest
setImageLayout(imageMemoryBarrier,
blitCmd,
image,
VK_IMAGE_ASPECT_COLOR_BIT,
VK_IMAGE_LAYOUT_UNDEFINED,
VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, imageMemoryBarrier.subresourceRange,
VK_PIPELINE_STAGE_TRANSFER_BIT,
VK_PIPELINE_STAGE_HOST_BIT);
// Do blit operation from previous mip level
vkCmdBlitImage(blitCmd, image, VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL, image,
VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, 1, &imageBlit, VK_FILTER_LINEAR);
setImageLayout(imageMemoryBarrier, blitCmd, image, VK_IMAGE_ASPECT_COLOR_BIT,
VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL, imageMemoryBarrier.subresourceRange,
VK_PIPELINE_STAGE_HOST_BIT,
VK_PIPELINE_STAGE_TRANSFER_BIT);
}
}

Answer 1

I don't see baseArrayLayer of the imageBlit.srcSubresource and imageBlit.dstSubresource set to j. Which is probably your immediate problem.
Also your barriers seem bad to me. Only the top mip needs to be synchronized with host. But even so VK_PIPELINE_STAGE_HOST_BIT should not be necessary, because there is an exception for vkQueueSubmit saying it does this kind of synchronization implicitly if host writes ended before it being called (6.9. Host Write Ordering Guarantees and reminded in the Note in 6.1.3. Access Types).