为什么我的 wgpu 绑定组中只能有一个纹理绑定？

Question

我目前有一个BindGroup和BindGroupLayout ，如下所示：

let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
    label: None,
    entries: &[wgpu::BindGroupLayoutEntry {
        binding: 0,
        visibility: wgpu::ShaderStages::FRAGMENT,
        ty: wgpu::BindingType::Texture {
            sample_type: wgpu::TextureSampleType::Float { filterable: true },
            view_dimension: wgpu::TextureViewDimension::D2,
            multisampled: false,
        },
        count: None,
    }],
});

let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
    label: None,
    entries: &[wgpu::BindGroupEntry {
        binding: 0,
        resource: wgpu::BindingResource::TextureView(&target),
    }],
    layout: &bind_group_layout,
});

并按需要工作。

对于上下文：我在渲染过程中使用这些来进行后期处理。

现在我的着色器中还需要一个Sampler器。 首先我创建了Sampler

let linear_sampler = device.create_sampler(&wgpu::SamplerDescriptor {
    mag_filter: wgpu::FilterMode::Nearest,
    min_filter: wgpu::FilterMode::Nearest,
    mipmap_filter: wgpu::FilterMode::Nearest,
    ..Default::default()
});

并将其添加到布局和绑定组中，如下所示：

let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
    label: None,
    entries: &[
        wgpu::BindGroupLayoutEntry {
            binding: 0,
            visibility: wgpu::ShaderStages::FRAGMENT,
            ty: wgpu::BindingType::Texture {
                sample_type: wgpu::TextureSampleType::Float { filterable: true },
                view_dimension: wgpu::TextureViewDimension::D2,
                multisampled: false,
            },
            count: None,
        },
        wgpu::BindGroupLayoutEntry {
            binding: 1,
            visibility: wgpu::ShaderStages::FRAGMENT,
            ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::NonFiltering),
            count: None,
        },
    ],
});

let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
    label: None,
    entries: &[
        wgpu::BindGroupEntry {
            binding: 0,
            resource: wgpu::BindingResource::TextureView(&target),
        },
        wgpu::BindGroupEntry {
            binding: 1,
            resource: wgpu::BindingResource::Sampler(&linear_sampler),
        },
    ],
    layout: &bind_group_layout,
});

但是，当我现在运行我的代码时，会得到一个ValidationError说：

thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In a RenderPass
      note: encoder = `<CommandBuffer-(0, 2, Metal)>`
    In a draw command, indexed:false indirect:false
      note: render pipeline = `<RenderPipeline-(1, 1, Metal)>`
    the pipeline layout, associated with the current render pipeline, contains a bind group layout at index 0 which is incompatible with the bind group layout associated with the bind group at 0

我注意到Metal和DirectX 12上的行为相同。 我还注意到，当我只添加一个采样器或添加两个纹理绑定时，我会遇到同样的错误，如下所示：

let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
    label: None,
    entries: &[
        wgpu::BindGroupLayoutEntry {
            binding: 0,
            visibility: wgpu::ShaderStages::FRAGMENT,
            ty: wgpu::BindingType::Texture {
                sample_type: wgpu::TextureSampleType::Float { filterable: true },
                view_dimension: wgpu::TextureViewDimension::D2,
                multisampled: false,
            },
            count: None,
        },
        wgpu::BindGroupLayoutEntry {
            binding: 1,
            visibility: wgpu::ShaderStages::FRAGMENT,
            ty: wgpu::BindingType::Texture {
                sample_type: wgpu::TextureSampleType::Float { filterable: true },
                view_dimension: wgpu::TextureViewDimension::D2,
                multisampled: false,
            },
            count: None,
        },
    ],
});

let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
    label: None,
    entries: &[
        wgpu::BindGroupEntry {
            binding: 0,
            resource: wgpu::BindingResource::TextureView(&target),
        },
        wgpu::BindGroupEntry {
            binding: 1,
            resource: wgpu::BindingResource::TextureView(&target),
        },
    ],
    layout: &bind_group_layout,
});

所以我发现唯一有效的配置是当绑定组和布局只包含一个纹理绑定时。

有谁知道为什么会这样？

完整的代码可以在这里找到。 失败的代码在src/fxaa/中，可以使用cargo run --example triangle进行测试，原始工作代码在src/grayscale/中，可以使用cargo run --example text 。 为了简洁起见，我省略了着色器，因为它们的内容似乎并不重要，但它们也可以在上面链接的 repo 中找到。

Answer 1

因为在fn resize(&mut self, device: &wgpu::Device, size: &wgpu::Extent3d)中，您创建了一个与已绑定的bind_group_layout bind_group

如果重新创建一个新的bind_group_layout ，您还需要重新创建一个新的 pipeline 和pipeline_layout 。