docs: public void addPostEffect(GVRMaterial postEffectData) {
          GVRContext ctx = getGVRContext();
  
          if (mPostEffects == null)
          {
              mPostEffects = new GVRRenderData(ctx, postEffectData);
              GVRMesh dummyMesh = new GVRMesh(getGVRContext(),"float3 a_position float2 a_texcoord");
              mPostEffects.setMesh(dummyMesh);
              NativeCamera.setPostEffect(getNative(), mPostEffects.getNative());
              mPostEffects.setCullFace(GVRRenderPass.GVRCullFaceEnum.None);
          }
          else
          {
              GVRRenderPass rpass = new GVRRenderPass(ctx, postEffectData);
              rpass.setCullFace(GVRRenderPass.GVRCullFaceEnum.None);
              mPostEffects.addPass(rpass);
          }
      }