Vulkan Backend image rendering. Image sampler always 'REPEAT'

[rytisss]

Version/Branch of Dear ImGui:

Version: 1.88
Branch: docking

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_vulkan.cpp
Compiler: Visual Studio C++ 2022
Operating System: Windows 10

I have a problem with texture visualization, I am trying to visualize the texture (picture) and clamp the image to the border. However, as much as I try to change the parameters in the sampler, I still get the repetitive pattern:

The code for the sampler:

        VkSamplerCreateInfo samplerInfo{};
	samplerInfo.sType = VK_STRUCTURE_TYPE_SAMPLER_CREATE_INFO;
	samplerInfo.magFilter = VK_FILTER_LINEAR;
	samplerInfo.minFilter = VK_FILTER_LINEAR;
	samplerInfo.addressModeU = VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_BORDER;
	samplerInfo.addressModeV = VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_BORDER;
	samplerInfo.addressModeW = VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_BORDER;
	samplerInfo.anisotropyEnable = VK_FALSE;
	samplerInfo.maxAnisotropy = 1.0f;
	samplerInfo.borderColor = VK_BORDER_COLOR_INT_OPAQUE_BLACK;
	samplerInfo.unnormalizedCoordinates = VK_FALSE;
	samplerInfo.compareEnable = VK_FALSE;
	samplerInfo.compareOp = VK_COMPARE_OP_ALWAYS;
	samplerInfo.mipmapMode = VK_SAMPLER_MIPMAP_MODE_NEAREST;
	samplerInfo.mipLodBias = 0.0f;
	samplerInfo.minLod = 0.0f;
	samplerInfo.maxLod = 0.0f;
	if (vkCreateSampler(m_info.Device, &samplerInfo, nullptr, &m_textureSampler) != VK_SUCCESS)
	{
		throw std::runtime_error("failed to create texture sampler!");
	}

Even when VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_BORDER or VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE is set, the results are the same (see image above). It seems that sampling is all the time VK_SAMPLER_ADDRESS_MODE_REPEAT.

To create a descriptor set (VkDescriptorSet), I am using:
m_descriptorSet = ImGui_ImplVulkan_AddTexture(m_textureSampler, m_textureImageView, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);

And to add an image:

ImGui::PushID((void*)(intptr_t)m_descriptorSet);
ImGui::GetWindowDrawList()->AddImageQuad(
					(ImTextureID)(m_descriptorSet),
					m_canvasTopLeft,
					m_canvasTopRight,
					m_canvasBottomRight,
					m_canvasBottomLeft,
					m_uv_0,
					m_uv_1,
					m_uv_2,
					m_uv_3,
					IM_COL32_WHITE);
ImGui::PopID();

It is sampling outside of image regions (outside should be with defined color), however, I get repetitive image patterns all the time (similar to repeat sampling mode).

I am wondering if there are any options set by default in the ImGui Vulkan backend that might interfere with this texture sampling (or override it)? Any help and hints are appreciated!

Might be related to #914

[rytisss]

Just a note, that same image visualization approach with OpenGL3 work perfectly fine in ImGUI with borders clamping:

[ghost]

Hi， @rytisss @ocornut
I also notify this problem, the mistake is that ImGui Vulkan backend use a common DescriptorSetLayout to create combiner image descriptorset, and when create DescriptorSetLayout, imgui fill font's sampler as a pImmutableSamplers.

But in vulkan spec, when pImmutableSamplers no NULL, pipeline will default use these init sampler and never dynamic switch sampler.

So the resolve method is just keep pImmutableSamplers is NULL like this:

[rytisss]

Hi @qiutanguu ,
Thank You so much for your comment and suggestion. And indeed it fixes the problem! I commented out the line in imgui_impl_vulkan.cpp as suggested and it is working as expected now with the clamp to boarders!

Line commented (

imgui/backends/imgui_impl_vulkan.cpp

Line 972 in 8cbd391

binding[0].pImmutableSamplers = sampler;

):

Result:

[ocornut]

It would be good to find a solution that doesn’t requires making a modification to the backend otherwise you aren’t going to easily update your copy.

this may need to be designed into a backend change.

[rytisss]

Indeed, totally agree. This is just a temporary fix. I will reopen the issue.

Maybe someone who is more experienced in Vulkan backend could give a suggestion if it is the proper way of solving this issue.

[martin-ejdestig]

I think that is all there is to it, pImmutableSamplers just needs to not be set. From https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VkDescriptorSetLayoutBinding.html :

pImmutableSamplers affects initialization of samplers. If descriptorType specifies a VK_DESCRIPTOR_TYPE_SAMPLER or VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER type descriptor, then pImmutableSamplers can be used to initialize a set of immutable samplers. Immutable samplers are permanently bound into the set layout and must not be changed; updating a VK_DESCRIPTOR_TYPE_SAMPLER descriptor with immutable samplers is not allowed and updates to a VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER descriptor with immutable samplers does not modify the samplers (the image views are updated, but the sampler updates are ignored).

(There are two vkCreateDescriptorSetLayout() calls though. Not sure why. Should be removed in both places, I think.)

[epajarre]

Just a a note, but I think I also met this problem. In my case have not noticed any visual issues, but when I show buttons with custom Texture in them, Vulkan validation layers will show an error:

VUID-vkCmdBindDescriptorSets-pDescriptorSets-00358(ERROR / SPEC): msgNum: -507995293 - Validation Error: [ VUID-vkCmdBindDescriptorSets-pDescriptorSets-00358 ] Object 0: handle = 0x67d8fc00000f097d, type = VK_OBJECT_TYPE_DESCRIPTOR_SET; | MessageID = 0xe1b89b63 | vkCmdBindDescriptorSets(): descriptorSet #0 being bound is not compatible with overlapping descriptorSetLayout at index 0 of VkPipelineLayout 0xb76ed0000000074b[] due to: Immutable samplers from binding 0 in pipeline layout VkDescriptorSetLayout 0x2193b1000000074a[] do not match the immutable samplers in the layout currently bound (VkDescriptorSetLayout 0xb12fb2000000002c[]). The Vulkan spec states: Each element of pDescriptorSets must have been allocated with a VkDescriptorSetLayout that matches (is the same as, or identically defined as) the VkDescriptorSetLayout at set n in layout, where n is the sum of firstSet and the index into pDescriptorSets (https://vulkan.lunarg.com/doc/view/1.3.224.1/windows/1.3-extensions/vkspec.html#VUID-vkCmdBindDescriptorSets-pDescriptorSets-00358)

Dropping the setting of pImmutableSamplers in backend fixes the validation error, and I have so far not noticed any problems with that.

[ocornut]

Merged fix e5d5186. Thanks a lot @martin-ejdestig and @rytisss!