Hello gaetan73,
I thought that you are using version 1.4.0 pre-release and have imported the dense cloud.
You can do that in the version 1.3.4 for mesh using the following Python code:
import PhotoScan
chunk = PhotoScan.app.document.chunk
for face in chunk.model.faces:
face.vertices = (face.vertices[0], face.vertices[2], face.vertices[1])
Then you may need to switch to another view mode (sparse cloud, for example) and switch back to solid view.