Wood Shader
What texture coordinate space is required for the shader to be displayed?
This shader is designed to work properly in UV space, nevertheless, in some cases it work just fine in other spaces as well.
Why do some textures appear blank, flickering, or corrupted?
Most complex nodes in some cases may produce displaying issues in specific render engines. To avoid this, try enabling Open Shading Language check box in render properties panel. Switching to UV input coordinates can also be useful to get rid of the problem.