VisionOS Metal Sample issue with clearColor

Question

_clemzio_ OP

Created Apr ’24

Replies 2

Boosts 0

Participants 1

Hi everyone,

This happens with Xcode 15.3 (15E204a) and visionOS 1.1.2 (21O231).

To reproduce this issue, simply create a new VisionOS app with Metal (see below).

Screenshot A

Then simply change the following piece of code in Renderer.swift:

func renderFrame() {
        [...]
        // Set the clear color red channel to 1.0 instead of 0.0.
        renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1.0, green: 0.0, blue: 0.0, alpha: 0.0)
        [...]
}

On the simulator it works as expected while on device it will show a black background with red jagged edges (see below).

Screenshot B

Answered by _clemzio_ in 788555022

Hey everyone, I found a better workaround for this issue. After debugging it further with a GPU Frame capture, it came to my attention that the compositor will create a segmentation mask for safety reason based on the depth of the rendered content. The mask will cut off roughly at the edges where the depth goes from 0.0 to a non-zero value, creating the jaggies seen on the screenshot above. The solution to this problem was to simply set the depth clear value to a very small non-zero value:

depthStateDescriptor.depthCompareFunction = .greater // Back to normal
renderPassDescriptor.depthAttachment.clearDepth = Double.ulpOfOne // slightly-higher-than-zero depth value by default

Hope this helps other people.

The

Boost

Answer 1

_clemzio_ OP

Apr ’24

It seems that a (not ideal) workaround is to do the following:

renderPassDescriptor.depthAttachment.clearDepth = 1.0  // instead of 0.0

and

depthStateDescriptor.depthCompareFunction = .always // instead of MTLCompareFunction.greater

0

Answer 2

_clemzio_ OP

1w

Accepted Answer

Hey everyone, I found a better workaround for this issue. After debugging it further with a GPU Frame capture, it came to my attention that the compositor will create a segmentation mask for safety reason based on the depth of the rendered content. The mask will cut off roughly at the edges where the depth goes from 0.0 to a non-zero value, creating the jaggies seen on the screenshot above. The solution to this problem was to simply set the depth clear value to a very small non-zero value:

depthStateDescriptor.depthCompareFunction = .greater // Back to normal
renderPassDescriptor.depthAttachment.clearDepth = Double.ulpOfOne // slightly-higher-than-zero depth value by default

Hope this helps other people.

The

0