Function render_solid_offscreen 

pub fn render_solid_offscreen(
    topo: &Topology,
    solid: SolidId,
    cam: &Camera,
    opts: &RenderOpts,
) -> Result<RenderOutput, RenderError>

Render a solid offscreen to a shaded color image and a face-id buffer.

Tessellates solid, sets up a wgpu device (trying a real GPU first, then a software fallback), rasterizes the mesh (and edges, if RenderOpts::edges) into off-screen targets, and reads them back.

Errors

• RenderError::InvalidSize if opts.width or opts.height is zero.
• RenderError::NoAdapter if no wgpu adapter (GPU or software) exists.
• RenderError::DeviceRequest / RenderError::BufferMap / RenderError::Poll on GPU setup or readback failure.
• RenderError::Operations if tessellating the solid fails.