Override imageview swizzles for channel replacement edge cases
When we decompress ETC2 RGB into a 4-channel texture, *almost*
everything just works as long as we ensure the alpha channel has the
correct values -- except that to the sampler, this is now a 4-channel
texture and so no channel replacement will be performed.
This interacts badly with border texel replacement, which occurs before
channel replacement. When a transparent border mode is used, we end up
with non-1 values in the returned alpha channel, which is wrong.
Instead, drive missing channels to 0/1 with the swizzle, which we
control independently of the texture format.
Bug: b/119620767
Test: dEQP-VK.pipeline.sampler.*
Change-Id: I2816e18fc1c36bd4de51a3e3871c75c7dc1b8867
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31388
Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
diff --git a/src/Vulkan/VkImageView.cpp b/src/Vulkan/VkImageView.cpp
index 9abefd6..1cdad2b 100644
--- a/src/Vulkan/VkImageView.cpp
+++ b/src/Vulkan/VkImageView.cpp
@@ -17,14 +17,28 @@
namespace
{
- VkComponentMapping ResolveIdentityMapping(VkComponentMapping m)
+ VkComponentMapping ResolveComponentMapping(VkComponentMapping m, vk::Format format)
{
- return {
- (m.r == VK_COMPONENT_SWIZZLE_IDENTITY) ? VK_COMPONENT_SWIZZLE_R : m.r,
- (m.g == VK_COMPONENT_SWIZZLE_IDENTITY) ? VK_COMPONENT_SWIZZLE_G : m.g,
- (m.b == VK_COMPONENT_SWIZZLE_IDENTITY) ? VK_COMPONENT_SWIZZLE_B : m.b,
- (m.a == VK_COMPONENT_SWIZZLE_IDENTITY) ? VK_COMPONENT_SWIZZLE_A : m.a,
+ if (m.r == VK_COMPONENT_SWIZZLE_IDENTITY) m.r = VK_COMPONENT_SWIZZLE_R;
+ if (m.g == VK_COMPONENT_SWIZZLE_IDENTITY) m.g = VK_COMPONENT_SWIZZLE_G;
+ if (m.b == VK_COMPONENT_SWIZZLE_IDENTITY) m.b = VK_COMPONENT_SWIZZLE_B;
+ if (m.a == VK_COMPONENT_SWIZZLE_IDENTITY) m.a = VK_COMPONENT_SWIZZLE_A;
+
+ // Replace non-present components with zero/one swizzles so that the sampler
+ // will give us correct interactions between channel replacement and texel replacement,
+ // where we've had to invent new channels behind the app's back (eg transparent decompression
+ // of ETC2 RGB -> BGRA8)
+ VkComponentSwizzle table[] = {
+ VK_COMPONENT_SWIZZLE_IDENTITY,
+ VK_COMPONENT_SWIZZLE_ZERO,
+ VK_COMPONENT_SWIZZLE_ONE,
+ VK_COMPONENT_SWIZZLE_R,
+ format.componentCount() < 2 ? VK_COMPONENT_SWIZZLE_ZERO : VK_COMPONENT_SWIZZLE_G,
+ format.componentCount() < 3 ? VK_COMPONENT_SWIZZLE_ZERO : VK_COMPONENT_SWIZZLE_B,
+ format.componentCount() < 4 ? VK_COMPONENT_SWIZZLE_ONE : VK_COMPONENT_SWIZZLE_A,
};
+
+ return {table[m.r], table[m.g], table[m.b], table[m.a]};
}
VkImageSubresourceRange ResolveRemainingLevelsLayers(VkImageSubresourceRange range, const vk::Image *image)
@@ -46,7 +60,7 @@
ImageView::ImageView(const VkImageViewCreateInfo* pCreateInfo, void* mem) :
image(Cast(pCreateInfo->image)), viewType(pCreateInfo->viewType), format(pCreateInfo->format),
- components(ResolveIdentityMapping(pCreateInfo->components)),
+ components(ResolveComponentMapping(pCreateInfo->components, format)),
subresourceRange(ResolveRemainingLevelsLayers(pCreateInfo->subresourceRange, image))
{
}
