Expression-based shader text is:
---
shader expr_0 (
    float s = u [[ int interpolated=1 ]],
    float t = v [[ int interpolated=1 ]],
    output color result = 0,
    output float alpha = 1,
  )
{
    result=color(u,v,0)
    ;
}
---
Shader group:
---
shader expr_0 expr_0_0 ;

---

Shader group "unnamed_group_1" layers are:
    expr_0_0


Output result to out.tif
