Controlling anti-aliasing when rendering to surface that is not the same size as the window

[casey]

I'd like to be able to render to a lower resolution and display it in a pixelated fashion, with nearest neighbor interpolation.

I have a resize function that configures the surface and sets up intermediate rendering targets. When I ignore the window size and use 32x32 pixels, it winds up being blurry. This is on MacOS. See below <details> elements for the resize function and output in both cases.

actual size

  pub(crate) fn resize(&mut self, size: PhysicalSize<u32>) {
    self.config.width = size.width.max(1);
    self.config.height = size.height.max(1);
    self.surface.configure(&self.device, &self.config);
    for target in self.targets.iter_mut() {
      *target = Target::new(
        &self.bind_group_layout,
        &self.config,
        &self.device,
        &self.sampler,
        self.texture_format,
        &self.uniform_buffer,
      );
    }
  }

32x32

  pub(crate) fn resize(&mut self, size: PhysicalSize<u32>) {
    self.config.width = 32;
    self.config.height = 32;
    self.surface.configure(&self.device, &self.config);
    for target in self.targets.iter_mut() {
      *target = Target::new(
        &self.bind_group_layout,
        &self.config,
        &self.device,
        &self.sampler,
        self.texture_format,
        &self.uniform_buffer,
      );
    }
  }

I looked at the wgpu docs, but couldn't find anything that looked like it might control whether or not the surface is displayed in an anti-aliased fashion. I also looked at the WebGPU spec, but couldn't find anything there either.

Is this something that can be controlled from wgpu/WebGPU? Or is this something which is up to the underlying surface/windowing implementation? Perhaps it can be controlled by being more explicit with winit initializing?

[cwfitzgerald]

The expected flow is to render to a literal 32x32 image, then render that image yourself to the swapchain of normal size.

Right now it's technically not defined the behavior if your swapchain is the wrong size.

[casey]

Thanks for the answer!