Optional : specifies the clear color. If not specified or if the clear color matches the fast clear color (and Viewport is zero), the clear will be done with render pass clear actions :
RenderGraphUtils.h
FirstMipIndex
uint32
Specifies which mip(s) to clear.
RenderGraphUtils.h
FirstSliceIndex
uint32
For texture arrays, specifies which slice(s) to clear.
RenderGraphUtils.h
NumMips
uint32
RenderGraphUtils.h
NumSlices
uint32
RenderGraphUtils.h
Viewport
FIntRect
Optional : specifies the area of the texture to clear (draws a quad to the requested viewport). If zero (and clear color is not passed or matches the fast clear color), the clear will be done with render pass clear actions :