# A negative entity-index **URL:** \ **Category:** Uncategorized\ **Created:** [June 29, 2021, 11:41am UTC](https://calculix.discourse.group/t/a-negative-entity-index/652 "2021-06-29T11:41:57Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![SergioP](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/sergiop/32/10_2.png) [@SergioP](https://calculix.discourse.group/u/SergioP)\ **Post date:** [June 30, 2022, 11:25am UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/24 "2022-06-30T11:25:24Z")
Have you properly created the mesh groups in Salome? Look in youtube, there are several tutorials of preprocessing in Salome and how to create groups asociated to the geometry. [![](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/3/36e08e5a3a116f60a51d10dc54126e402dddb111.jpeg "Salome-Platform & CalculiX. Using .UNV mesh format with CalculiX Launcher") ](https://www.youtube.com/watch?v=5n8ZCIM65ao) ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://calculix.discourse.group/u/jbr)\ **Post date:** [July 2, 2022, 4:59pm UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/25 "2022-07-02T16:59:52Z")
Have you tried using [PrePoMax](https://prepomax.fs.um.si/)? ---
**Author:** ![COCO](https://avatars.discourse-cdn.com/v4/letter/c/8797f3/32.png) [@COCO](https://calculix.discourse.group/u/COCO)\ **Post date:** [July 6, 2022, 9:30am UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/26 "2022-07-06T09:30:18Z")
Hi jbr, I haven’t tried using PrePoMax because I’m a freshman in these software about CAE. I just learnt from videos on youtube. Are you good at PrePoMax or any other software to generate mesh for calculix ? Best regard ---
**Author:** ![COCO](https://avatars.discourse-cdn.com/v4/letter/c/8797f3/32.png) [@COCO](https://calculix.discourse.group/u/COCO)\ **Post date:** [July 6, 2022, 9:40am UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/27 "2022-07-06T09:40:33Z")
Sorry for late, SergioP. I don’t know whether I have properly created the mesh groups in Salome. I upload the screenshot. The top and bottom of cylinder are outlet and inlet. Surface of cylinder is interface. Could you find the problem in my setup? ![1657100226(1)](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/28a726a8a50d86f3195d1b6b612bf4b66861cbbc.png) ---
**Author:** ![SergioP](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/sergiop/32/10_2.png) [@SergioP](https://calculix.discourse.group/u/SergioP)\ **Post date:** [July 6, 2022, 1:37pm UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/28 "2022-07-06T13:37:01Z")
Looks ok, but the best way to see the mesh groups in Salome, is using the Mesh module, there you can select and show each group and they will be displayed in the graphic area, you could even change the color individually for the better vieweing. In the upper left side will appear a nice color reference with the group’s name. ---
**Author:** ![COCO](https://avatars.discourse-cdn.com/v4/letter/c/8797f3/32.png) [@COCO](https://calculix.discourse.group/u/COCO)\ **Post date:** [July 7, 2022, 3:11am UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/29 "2022-07-07T03:11:20Z")
I’ve solved that problem. I didn’t create groups of nodes in mesh generation, which is the main reason that there is no data about NSET, NSET=Ninlet in .inp file. After I added groups of nodes, I could write the data into the files inlet.nam and outlet.nam. Thanks for your patience to help me. ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://calculix.discourse.group/u/jbr)\ **Post date:** [July 9, 2022, 5:36pm UTC](https://calculix.discourse.group/t/a-negative-entity-index/652/30 "2022-07-09T17:36:05Z")
@COCO , PrePoMax is great for newbies and there are sufficient videos on YouTube [PrePoMax search.](https://www.youtube.com/results?search_query=prepomax). Give it a try 🙂 . [Previous page](https://calculix.discourse.group/t/a-negative-entity-index/652.md?page=1)