I used a dome light but when i rendered it there is no ground (the green part of sketchup space) …also i tried to put my hdr in the Environment but the ground part is darker.how could i fix this
Even though I don’t see it mentioned anywhere here, I am assuming this is V-ray related question. You are better off asking V-ray questions in V-ray for SketchUp forum:
With that noted, ground in SketchUp is considered as empty space in V-ray. Consider using “infinite plane”.
The result of the image can be vastly different depending on how you are using hdr mapping. Things can be better answered in the other forum.