Known problems

Known problems

1) Graphic area is blank:

When running FEMGV on PC using OpenGL sometimes the graphics area is blank and the models cannot be seen.

The way OpenGL draws to the screen is influenced by the choice of "pixel format". A pixel format specifies several properties such as:

- Whether the pixel buffer is single- or double-buffered.

- Whether the pixel data colour representation is in RGBA or colour-index form.

- The number of bits used to store colour data.

- The number of bits used for the depth (z-axis) buffer.

Pixel formats are synonymous with visual classes in the Motif environment.

FEMGV attempts to select the best pixel format but sometimes, because of deficiencies in the underlying graphics system, it needs some user intervention.

In order to select a pixel format:

1. Run FEMGV from a DOS box and redirect standard output to a file (i.e., femgv6 > log)

2. Look at the output file log, you should see something like this

C:\fgv-work>type log

cb:rb gb bb:zb

1 DW OGL ACC+ RGB 16: 5/ 5/ 5: 0

2 DW OGL ACC+ DB RGB 16: 5/ 5/ 5: 0

3 DW OGL ACC+ RGB 16: 5/ 5/ 5:16

4 DW OGL ACC+ DB RGB 16: 5/ 5/ 5:16

5 DW OGL ACC+ RGB 16: 5/ 5/ 5:32

6 DW OGL ACC+ DB RGB 16: 5/ 5/ 5:32

7 DW OGL ACC- RGB 16: 5/ 5/ 5:32

8 DW OGL ACC- RGB 16: 5/ 5/ 5:16

9 DW OGL ACC- DB RGB 16: 5/ 5/ 5:32

10 DW OGL ACC- DB RGB 16: 5/ 5/ 5:16

11 DW OGL ACC- CI 16: 5/ 5/ 5:32

12 DW OGL ACC- CI 16: 5/ 5/ 5:16

13 DW OGL ACC- DB CI 16: 5/ 5/ 5:32

14 DW OGL ACC- DB CI 16: 5/ 5/ 5:16

15 OGL ACC- RGB 24: 8/ 8/ 8:32

16 OGL ACC- RGB 24: 8/ 8/ 8:16

17 OGL ACC- CI 24: 8/ 8/ 8:32

18 OGL ACC- CI 24: 8/ 8/ 8:16

19 OGL ACC- RGB 32: 8/ 8/ 8:32

20 OGL ACC- RGB 32: 8/ 8/ 8:16

21 OGL ACC- CI 32: 8/ 8/ 8:32

22 OGL ACC- CI 32: 8/ 8/ 8:16

23 OGL ACC- RGB 8: 3/ 3/ 2:32

24 OGL ACC- RGB 8: 3/ 3/ 2:16

25 OGL ACC- CI 8: 3/ 3/ 2:32

26 OGL ACC- CI 8: 3/ 3/ 2:16

27 OGL ACC- RGB 4: 1/ 1/ 1:32

28 OGL ACC- RGB 4: 1/ 1/ 1:16

29 OGL ACC- CI 4: 1/ 1/ 1:32

30 OGL ACC- CI 4: 1/ 1/ 1:16

Using PixelFormat : 9

This is a list of ALL of the pixel formats available with your graphics card.

3. FEMGV has particular requirements and so we can narrow down the choice of candidate formats.

FEMGV requires:

- DW and OGL

- DB to give double buffering

- a Z-buffer (zb) of at least 16 bits

- a colour buffer of at least 16 bits

4. The most usual cause of screen blackness is trying to use an RGB pixel format when the graphics card can only cope with colour index (CI). So, say for example that pixel format 9

9 DW OGL ACC- DB RGB 16: 5/ 5/ 5:32

did not work on my machine, the chances are that number 13 would work

13 DW OGL ACC- DB CI 16: 5/ 5/ 5:32

Note that the only difference between 9 and 13 is that 9 is RGB and 13 is CI

5. To test a different pixel format rerun FEMGV like this

femgv6 -DefaultVisual 13 > log

Have a look at a model to see if the this new format has worked. If it is no better then check the log file. If you have selected an inappropriate format there will be a message telling why it is not suitable. You may need to try several formats!

Both the display resolution and the number of colours can affect the pixel formats available from your particular graphics card, if you cannot find a suitable format try changing the display properties of your screen.

6. Once you have found a pixel format that works you can either change the shortcut associated with FEMGV so that it runs 'femgv6 -DefaultVisual nn' or you can set the resource DefaultVisual in the femsys.ini file.

Femsys.*.OpenGL.DefaultVisual : nn

2) FEMGV status bar messages are not displayed:

It appears there is a bug in an older version of the custom controls DLL (comctl32.dll) such that messages sent to the status bar from within FEMGV (Processing, Drawing model, Generating mesh, etc) are not displayed.

Microsoft is aware of this and has kindly produced a patch to update the offending DLL.

To check if your DLL requires updating, locate the file in

a) C:\windows\system\ directory (Windows 95/98), or

b) C:\winnt\system32\ directory (Windows NT)

Look at the File/Properties/Version number, if it is less than 4.72.3110 it is likely that it requires updating.

If this is the case on your machine point your browser at http://support.microsoft.com/support/kb/articles/q186/1/76.asp

for information on how to upgrade your DLL.

3) Not enough memory to generate tetrahedral mesh:

In some cases where the model is large and requires a large number of tetrahedral elements to mesh it, the user might experience an error message indicating that there is not enough memory to mesh the model. FEMGV will recommend the required memory .

In order to increase the memory size, please use the following resource in FEMGV resource file (i.e., femsys.ini) and edit accordingly:

Femsys.*.Mestet.Memory

100

4) Element edge and face determination problems for elemental loads and contact surfaces:

When an elemental load (e.g. pressure) is applied to the edge of 2D elements or the faces of 3D elements, it is necessary to determine which element edges or faces are loaded. This information is used when displaying loads in FEMGEN (LABEL MESH LOADS) and it is also passed on to the interface program. Similarly, element edges or faces information can also be used by some interface programs when processing contact surfaces, e.g. in the ABAQUS environment. There are two situations where the determination of element edges or faces information is incorrect.

Firstly, the current algorithm only expects one edge or face of an element to be loaded and will return information on the first loaded edge or face that it finds. No information will be returned on any additional edges or faces of the element that are loaded. The picture below shows this situation in the 2D case.

[00d.wmf]

Secondly, the current algorithm may identify the wrong edge or face of an element as loaded. If an element has a relevant number of corner nodes that lie on the loaded part, the edge or face that contains these corner nodes will be considered loaded, although the entire edge (or face) may not necessarily lie on the geometric part, as shown in the figure below. Note that the figure also shows the first problem as two element edges are ignored.

[00e.wmf]

These examples show the problems in the 2D case. However, if these geometry were swept, the determination of the element faces of the solid elements would also be incorrect. These behaviours also apply when the geometric part (either a line adjacent to a surface mesh or a surface adjacent to a solid mesh) is defining a contact surface.

In both situations, it is recommended to refine the mesh so that there are more elements adjacent to the geometric part in question. Note that the above problems will only occur if the surface has been free meshed rather than mapped meshed.

This problem is being addressed and will be addresses shortly.

5) Postabaqus problems

The following problem have been encountered with the postabaqus program:

In a mode-based steady-state dynamic analysis, postabaqus processes the displacement magnitude and the phase data separately. These should be processed together as a complex result.

If you encounter such problems, please inform your FEMGV distributor.