What causes "only rectangle textures can be used as render target!" in FyroxEngine/Fyrox?

Create render-target textures with TextureKind::Rectangle { width, height }

only rectangle textures can be used as render target!

Error message

only rectangle textures can be used as render target!

What it means

The renderer computes the framebuffer size from the render-target texture; only TextureKind::Rectangle carries usable width/height for this purpose. Any other texture kind panics because it cannot serve as a render target.

Solutions

Create render-target textures with TextureKind::Rectangle { width, height }
Validate the texture kind before assigning it as a render target
Use RenderTarget::screen() or None when the window backbuffer is intended

Example fix

// before
let rt = Texture::new(ctx, TextureDescriptor { kind: TextureKind::D2 { width: 512, height: 512 }, ..});
// after
let rt = Texture::new(ctx, TextureDescriptor { kind: TextureKind::Rectangle { width: 512, height: 512 }, ..});

Defensive patterns

Strategy: validation

Validate before calling

assert!(matches!(rt.data_ref().kind(), TextureKind::Rectangle{..}));

Type guard

fn as_rect_kind(k: &TextureKind) -> Option<(u32,u32)> { if let TextureKind::Rectangle{width,height} = k { Some((*width,*height)) } else { None } }

Prevention

Use TextureKind::Rectangle for all render targets
Centralize render-target creation in one validated helper
Never assign sampled 2D textures as render targets

When it happens

Trigger: Setting a camera/scene render target to a texture with kind D2, Cube, or Volume and running a render pass.

Common situations: Creating offscreen render targets with the wrong TextureKind; reusing regular 2D sampled textures as render targets; following outdated tutorials.

Understand the failure class

Background: "is not a compatible type" / "cannot merge" errors: when a value's type doesn't match what the library requires — this error's family across 65 libraries.

Related errors

AI-assisted analysis of FyroxEngine/Fyrox@76c91aad8e (2026-09-10). Data as JSON: /api/errors/6487df2190599bcb. Report an issue: GitHub.

Appendix: source

Thrown at fyrox-impl/src/renderer/mod.rs:1311

        let backbuffer_width = self.frame_size.0 as f32;
        let backbuffer_height = self.frame_size.1 as f32;

        let window_viewport = Rect::new(0, 0, self.frame_size.0 as i32, self.frame_size.1 as i32);

        let frame_size = scene
            .rendering_options
            .render_target
            .as_ref()
            .map_or_else(
                // Use either backbuffer size
                || Vector2::new(backbuffer_width, backbuffer_height),
                // Or framebuffer size
                |rt| {
                    if let TextureKind::Rectangle { width, height } = rt.data_ref().kind() {
                        Vector2::new(width as f32, height as f32)
                    } else {
                        panic!("only rectangle textures can be used as render target!")
                    }
                },
            )
            // Clamp to [1.0; infinity] range.
            .sup(&Vector2::new(1.0, 1.0));

        let scene_render_data = match self.scene_data_map.entry(scene_handle) {
            Entry::Occupied(entry) => {
                let render_data = entry.into_mut();
                recreate_render_data_if_needed(
                    scene_handle,
                    &*self.server,
                    &mut render_data.scene_data,
                    frame_size,
                    FrameTextureKind::Rectangle,
                )?;
                render_data
            }

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