2.6
THE OPENGL PLOT PROGRAM Z88O
You may
illuminate a structure
with three different light sources or plot with hidden lines, both the
undeflected and the deflected structure. You may plot stresses and X, Y
and Z
deflections with a color range. You may plot a limited range of nodal
or
element numbers - a nice feature especially for large structures. A
printer or
plotter feature is not included into Z88O - and why - just do a screen
shot by Shift-Print into the clipboard and
proceed with Windows’ program Paint or Corel Paint.
Z88O
uses OpenGL so your computer must be able to deal with OpenGL graphics.
This is
true for all newer Windows machines and a quite cheap graphics card
will do
well. Anyway, it’s always a good idea to control the system settings -
sometimes you may turn on OpenGL hardware acceleration. On LINUX
systems you
should install the genuine NVIDIA graphics driver from www.nvidia.com if you’ve got a
NVIDIA
graphics card – the speed will increase heavily in contrast to the
standard
LIXUX graphics driver.
Of
course, you may define your choice of colors, the light features,
material
properties, the polygon offset in the parameter files Z88O.OGL (for
Windows)
and Z88.FCD (for LINUX/UNIX). Be careful with changes in Z88O.OGL
(Windows) or
Z88.FCD (UNIX/LINUX): You should have some proper knowledge about
OpenGL if you
want to change light effects etc. Otherwise you may pull a long face
because
nothing will work as you wish. Some hints are included into Z88O.OGL
and
Z88.FCD, however, i cannot give here an introduction into OpenGL.
Consult the
two basic books „OpenGL Programming Guide“ and „OpenGL Reference
Manual“ from
Addison-Wesley.
Start of Rendering:
When Z88O was launched the OpenGL subsystem is started and prepared to
go.
You’ll start rendering with the very first
Run pushbutton.
Needed
Files: |
Super
Struktures |
undeflected
FE Struktures |
deflected
FE Struktures |
Z88NI.TXT |
yes |
no |
no |
Z88I1.TXT |
no |
yes |
yes |
Z88I2.TXT |
no |
yes for displaying the boundary conditions |
yes for displaying the boundary conditions |
Z88I5.TXT |
no |
yes for displaying the surface and pressure loads |
yes for displaying the surface and pressure loads |
Z88O2.TXT |
no |
no |
yes |
Z88O5.TXT |
no |
yes for displaying the stresses in the Gauss points |
no |
Z88O8.TXT |
no |
yes for displaying the stresses in the corner nodes or
the average element stresses |
yes for displaying the stresses in the corner nodes or
the average element stresses |
Z88 deals with
these files
Rendering with Z88O: For
fastest operation Z88O connects the nodal points - and only the corner
points-
with straight lines, although for Serendipity elements the edges of the
elements are square or cubic curves. However, especially illuminated
scenes
need a huge amount of computational power. Please keep in mind: If a
part
renders pretty fast in your CAD system, Pro/ENGINEER for example, and
the same
part renders quite slowly in Z88O - this is normal business because CAD
systems
are „drawing“ only some outline curves. In contrast, FEA system have to
render every finite element i.e. compute the
normal vectors for any element surface, compute light effects for every
tetrahedron etc. Hidden line scenes put very heavy load on the CPU, too.
Thus, if you have
computed the von Mises stresses with
a Z88D run Z88O will show the von Mises stresses. If you want to
see now the Tresca stresses you must leave Z88O. Edit Z88I3.TXT,
enter the proper parameter (in this case, set the third entry to 3) and
re-run
Z88D. Then start Z88O again. This looks awkward
but don’t you know before starting the FE computations which type of
stresses
is suitable and correct for your task?
Plot
of deflections: You may plot the
undeflected or the
deflected structure. The enlargement factor is adjustable, with 100 as
the
default value for X, Y and Z. In addition, you may plot the deflections
for X,
for Y or for Z with color shading. This is a pretty nice feature for
large
spatial structures. You may plot the shaded colors for stresses or for
the
deflections or the hidden line display or the wire frame display with
the
deflected structure. The display of the stresses in Gauss points in
only
possible for undeflected structures.
|
3D |
2D |
BC |
undef. |
deflec. |
nodes |
elem. |
Light |
+ |
+ |
+ |
+ |
+ |
- |
- |
Hidden
Line |
+ |
- |
+ |
+ |
+ |
o |
- |
Wire
Frame |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
Stresses
in corner nodes |
+ |
+ |
- |
+ |
+ |
- |
- |
Stresses
aver. elements |
+ |
+ |
- |
+ |
+ |
- |
- |
Stresses
in Gauss points |
+ |
+ |
- |
+ |
- |
- |
+ |
Deflections
X |
+ |
+ |
- |
+ |
+ |
- |
- |
Deflections
Y |
+ |
+ |
- |
+ |
+ |
- |
- |
Deflections
Z |
+ |
+ |
- |
+ |
+ |
- |
- |
combination of the
different modes of Z88O
Hints
for the user for Zooming, Panning and Rotating:
1. You may work
without limitation
with the special keys for Windows (see below) or the pushbuttons for
UNIX. You
should use the special keys or the pushbuttons for precise zooming,
panning and
rotating. This is the default mode. Mouse navigation is turned off.
2. With Z88O you may
use mouse
navigation: Under Windows, press the mouse icon. Under UNIX, press the
pushbutton Keyboard/ Mouse: Now you
can
+ zoom with the
left mouse button pressed
+ pan with the
middle mouse
button pressed
+ rotate with the
right mouse
button pressed
This option fits well for limited zooming- and panning ranges and for fast but quite unprecise rotating. You may in addition use the special keys or pushbuttons but this mixed mode is not a real feature and may lead to unpredictable results because Z88O uses different calculations for both modes.
Special
key strokes for Windows and LINUX:
Prior:
increase zoom
Next:
decrease zoom
Cursor
left:
panning X
direction
Cursor
right:
panning X
direction
Cursor
up:
panning Y direction
Cursor
down:
panning Y direction
Home:
panning
Z direction
End:
panning Z direction
F2:
rotate around X
axis
F3:
rotate around X
axis
F4:
rotate around Y
axis
F5:
rotate around Y
axis
F6:
rotate around Z
axis
F7:
rotate around Z
axis
F8:
reset all
rotations to 0
The „coordinate system“:
OpenGL works with a Clipping Volume,
i.e. with a kind of cube, defined by Xmin
and Xmax in horizontal direction, by Ymin
and Ymax in vertical direction and Zmin
(points towards the user) and Zmax
(points away from the user). If you use a too-large zoom factor or if
you are
panning the structure too near to you then the range of Zmin
is exceeded and parts of the structure are laying outside the
viewing volume. This offers a nice chance to look into a structure.
Otherwise,
change the value of Zmin (default
entry is –100) to lower values, e.g. -1000: use Factors
> Z limit towards you. The following screenshots are
showing the situation:
Windows: piston of a BMW engine
(motorcycle F650GS)
Zlimit: default value –100.
Windows: piston of a BMW engine
(motorcycle F650GS)
Zlimit is –10, piston has slash cut.
The menu items of Z88O:
Name
of Structure File: Windows: the diskette icon.
UNIX: the File pushbutton
Choose
the structure file here. Enter name, if necessary with path. The new
stucture
is loaded. You’ll start rendering with the icon Go or
with the Run pushbutton.
This mode exists only for a first entry control of an undeflected
structure.
Please keep in mind: To use all
display modes, Z88O needs the files Z88I1.TXT (structure data),
Z88I2.TXT
(boundary conditions), Z88I5.TXT (surface and pressure loads, if
given),
Z88O2.TXT (the computed deflections), Z88O5.TXT (stresses from Z88D)
and
Z88O8.TXT (stresses from Z88D).
Deformation
Modes of the Structure: the proper icons or
pushbuttons
Plots
the undeflected structure or the deflected structure. You may do all
other
rendering operations with the undeflected structure or the deflected
structure.
Exception: displaying the Gauss stresses in a deflected
structure is not possible.
Caution Deflected: The
user must have executed a calculation of
displacements before using this function. Do a FEA run with Z88F or
Z88I1/Z88I2
or Z88I1/Z88PAR before using Z88O. Otherwise, some old files Z88O2.TXT
(displacements) from earlier Z88 runs are opened causing totally wrong
results!
Choice
of the 3D effects: the proper icons or
pushbuttons
Windows:
Hidden line plot of the BMW piston.
LINUX: Hidden line plot of the
BMW piston.
Drawing
Node and Element Numbers: Labels > No Labels, Nodes,
Elements,
Plot
the element numbers or the node numbers or skip numbering. You can
define
ranges from-to, e.g. plot the nodal
numbers from 11 to 19 or plot the element 3, i.e. from 3 to 3. Z88O
recalls
your entries even if you change to No
Labels. In Label all mode the
element and node numbers you have chosen before are plotted. If you
want to see
all numbers again but you have forgotten how many nodes and elements
are in
your structure you may enter a very high number e.g. from
1 to 10000000. Z88O computes then the exact number. Please
remember that you’ll only get rendered all desired labels on the
surfaces if
you are in Wire Frame mode. The other
modes may hide some labels. And labels inside a structure are usually
covered
by the tetrahedron and hexahedron surfaces.
Zooming:
Keyboard:
PRIOR and NEXT
mouse
navigation on:
left
mouse button pressed
Panning:
Keyboard:
X:
CURSOR LEFT and CURSOR RIGHT
Y:
CURSOR UP and CURSOR
DOWN
Z:
HOME and END
mouse
navigation on:
middle
mouse button pressed
Rotating:
Keyboard:
F2~F7: rotate in 10°
steps. F8 resets to 0.
Menu:
Faktors > Rotations 3D
mouse
navigation on:
right
mouse button pressed
Enlarging
Deflections:
Menu:
Factors > Deflections > FUX, FUY, FUZ
Some
remarks on stresses:
If
you did before a stress
calculation
with Z88D (this is possible and useful for all element types except for
beams
No.2, No.13 and cams No.5), then you may plot the von
Mises/principal/Tresca stresses either in the corner nodes or
as mean values per each element or in the Gauss points. And before
running the
stress processor Z88D you really had to calculate the displacements by
running
Z88F or one of the sparse matrix solvers. Thus, the sequence is:
Caution: The operator is responsible for first running a stress calculation by Z88D before using this function. Otherwise some old stress files Z88O5.TXT and Z88O8.TXT from earlier calculations are read in causing totally wrong results!
Automatic Scaling: the
appropriate icon or pushbutton
The
Autoscale function takes care that
structures will completely fit on the screen. Autoscale activates
automatically
if a new structure is loaded.
Height
Ratio FYCOR: Files Z88O.OGL and Z88.FCD
The
height ratio can be adjusted to the monitor customization. Therefore,
the entry
FYCOR exists in Z88O.OGL (Windows) or Z88.FCD (UNIX). Load a perfectly
circular
or perfectly square structure and modify FYCOR until this structure is
plotted
perfectly circular or square on your monitor. Please keep in mind that
FYCOR is
loaded with the start of Z88O, so you must re-launch Z88O after a
modification in
the files. You need to make this modification only once.