The downsample shader doesn't support texture format

Error message

The downsample shader doesn't support texture format {:?}

What it means

specialize() in DownsamplePipeline panics when texture_format_shader_def returns None for the requested texture format, meaning the mip-generation/downsample compute shader has no shader def for that format. It's a hard panic, not a recoverable error, because the pipeline cannot be created for unsupported formats.

Solutions

Use a supported texture format (e.g. Rgba8Unorm, Rgba16Float) for textures passed to downsample/mip generation
Add a mapping in texture_format_shader_def and the shader for your format if you control the fork
Fall back to CPU-side mip generation or a custom pipeline for exotic formats

Example fix

// before
let image = Image::new_fill(size, TextureDimension::D2, &[0;2], TextureFormat::Rg16Float, ...);

// after
let image = Image::new_fill(size, TextureDimension::D2, &[0;4], TextureFormat::Rgba16Float, ...);

Defensive patterns

Strategy: fallback

Validate before calling

const SUPPORTED: &[TextureFormat] = &[TextureFormat::Rgba8Unorm, TextureFormat::Rgba16Float];
fn downsample_supported(f: TextureFormat) -> bool { SUPPORTED.contains(&f) }

Type guard

fn downsample_supported(f: TextureFormat) -> bool {
    matches!(f, TextureFormat::Rgba8Unorm | TextureFormat::Rgba16Float | TextureFormat::Rgba32Float)
}

Try / catch

if downsample_supported(format) { spawn downsample pipeline } else { // fallback: CPU mip generation or convert image to supported format }

Prevention

Stick to common RGBA color formats for textures needing mip generation
Check texture_format_shader_def mappings when adding new formats

When it happens

Trigger: Creating/downsizing a texture in a format the downsample shader doesn't support (e.g. non-standard or 64-bit color formats) and then running the mip generation / downsample pipeline with that format as the DownsamplePipelineKey.

Common situations: Using a custom render target texture format (e.g. Rgb16Float variants, depth formats) that bevy_core_pipeline's downsample shader lacks mappings for; upgrading Bevy and relying on a format no longer supported.

Related errors

AI-assisted analysis of bevyengine/bevy@a62cce8c05 (2026-09-19). Data as JSON: /api/errors/ffed877266e64b2a. Report an issue: GitHub.

Appendix: source

Thrown at crates/bevy_core_pipeline/src/mip_generation/mod.rs:145

/// Note that, despite the name, the single-pass downsampling shader has two
/// passes, not one. This is because WGSL doesn't presently support
/// globally-coherent buffers; the only way to have a synchronization point is
/// to issue a second dispatch.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum DownsamplePass {
    /// Produces mip levels 1 to 6.
    First,
    /// Produces mip levels 7 to 12.
    Second,
}

impl SpecializedComputePipeline for DownsamplePipeline {
    type Key = DownsamplePipelineKey;

    fn specialize(&self, key: Self::Key) -> ComputePipelineDescriptor {
        let mut shader_defs = vec![
            texture_format_shader_def(key.texture_format).unwrap_or_else(|| {
                panic!(
                    "The downsample shader doesn't support texture format {:?}",
                    key.texture_format
                )
            }),
            ShaderDefVal::Bool("ARRAY_TEXTURE".into(), key.array_texture),
        ];
        if self.subgroup_support {
            shader_defs.push("SUBGROUP_SUPPORT".into());
        }
        shader_defs.push(
            match (key.combine_bind_groups, key.pass) {
                (true, _) => "COMBINE_BIND_GROUP",
                (false, DownsamplePass::First) => "SPLIT_BIND_GROUP_FIRST",
                (false, DownsamplePass::Second) => "SPLIT_BIND_GROUP_SECOND",
            }
            .into(),
        );

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