PCL problems in Ubuntu 20.04. how to get it running?

Question

Make Error at CMakeLists.txt:12 (find_package):
  By not providing "FindPCL.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "PCL", but
  CMake did not find one.

  Could not find a package configuration file provided by "PCL" (requested
  version 1.11) with any of the following names:

    PCLConfig.cmake
    pcl-config.cmake

  Add the installation prefix of "PCL" to CMAKE_PREFIX_PATH or set "PCL_DIR"
  to a directory containing one of the above files.  If "PCL" provides a
  separate development package or SDK, be sure it has been installed.
cmake_minimum_required(VERSION 2.8 FATAL_ERROR)

add_definitions(-std=c++11)

set(CXX_FLAGS "-Wall")
set(CMAKE_CXX_FLAGS, "${CXX_FLAGS}")

project(playback)

set(PCL_DIR "/opt/pcl/")

find_package(PCL 1.11 REQUIRED)

include_directories(${PCL_INCLUDE_DIRS})
link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})
list(REMOVE_ITEM PCL_LIBRARIES "vtkproj4")


add_executable (environment src/environment.cpp src/render/render.cpp src/processPointClouds.cpp)
target_link_libraries (environment ${PCL_LIBRARIES})

I have installed PCL successfully , but cant get the cmake to find it . PCL is installed in opt/pcl and I even tried to set it . Still doesn't work, HELP PLEASE?