Hello my friends,

This week, I would like to explain some settings that affect the screen display of 3-D solid models and their print out. In order to make photorealistic rendering, you have to prepare smooth surfaces. Besides, in industry, prior to moving on to the mass production phase, prototypes are manufactured. For the STL output made up of 3-D entities, you need surfaces having good quality.  There may be other examples in a similar manner.

In AutoCAD, two types of view modes are available:

o Wireframe view: In this view mode, it is an ideal view mode to see the intersection edges of surfaces that are not in the same plane.

o 3-D Solid Modeling :When you use _HIDE or _RENDER commands, AutoCAD builds a mesh surface (POLYMESH) for solid entities. The reason why this surface is built is to hide the separation lines of background entities and to calculate light / shadow view while rendering. After regenerating the drawing with _REGEN command, solid models return back to wireframe, thus their previous view.

Screen display and output of 3-D models are determined by these system variables:

1. DISPSILH
2. ISOLINES
3. FACETRES
4. FACETRATIO

These four important variables have no effect on _VSCURRENT command. I will explain visual styles in a more detailed way in my coming articles. They are HALOGAP, OBSCUREDCOLOR, OBSCUREDLTYPE, INTERSECTIONDISPLAY, INTERSECTIONCOLOR and system variables starting with VS.

1. DISPSILH System variable:

You can control the display of boundary lines of solid entities that are in Wireframe mode, by using “DISPSILH” system variable (Fig. 1-2). It is enough to enter the value of this variable as 1 (one) in order to view the boundary lines of the solid entities that we have defined as silhouette. Then use REGEN command to refresh the drawing. REGEN command regenerates the screen display as it is entered from the command line.

In HIDE mode, solid modes are only displayed as silhouette as shown in Fig. 2-2. In order to cancel the additional lines that are related to FACETRES system variable, enter the value of DISPSILH system variable as 1 (one). By this way, you can take print-out by simplifying the complex view.

2. ISOLINES System variable:

It determines the number of lines that is used to display the curved surfaces of solids in wireframe mode. ISOLINES system variable accepts only values in the range of 0 (zero) and 2047. ISOLINES system variable, with its default value of 4, places 4 lines between the curved lines by standard. Note that, higher values will decrease the displaying performance and increase the refreshing time.

ISOLINES system variable affects only on curved surfaces cylinder, cone, and dome. It is possible to adjust the display of mesh view of solid entities having planar surfaces by using SURFU and SURFV system variables. You can easily see the difference by assigning different values to these variables, which determine the mesh resolution in M- and N- directions, before using the _PLANESURF command.

Note: You must refresh the screen display by REGEN command after changing the system variables!

3. FACETRES System Variable:

FACETRES system variable determines the display quality of solid entities. Values in the range of 0.01 and 10 can be assigned to this system variable, default values of which is 0.5. It is used to adjust the display quality by assigning high values after HIDE, SHADE, SHADEMODE and RENDER commands and to form up smooth surfaces. By this way, AutoCAD builds up more mesh surfaces (POLYMESH).

Before exporting your solid models to 3DS MAX program, you can obtain much better results for the entities to be smoothened.

If you assign value of 1 (one) to the DISPSILH system variable, Polymesh surfaces do not appear, however, it still affects the smoothness of circles and arcs. This difference is clearly seen in the print outs.

4. FACETRATIO System Variable:

It controls the distribution of Polymesh.

When you assign the value of 1 (one) polymesh, not only affects the radius of the cylinder but also its height. Distribution of polymesh along the surface is related to the ratio of radius and height.

There is no need to play with this variable, default value of which is 0 (zero). I cannot find a practical example. If you have experience related to this variable, do not hesitate to post a comment, let’s learn from each other.

Control mechanism: System varaible, “SolidCheck“

It is possible to use the values specified below for this variable, default value of which is 1 (one):

1 (one) = After making changes over the solid models with SOLIDEDIT command, it starts the automatic debugging process of AutoCAD.

After entering SOLIDEDIT command, a message is displayed which reminds the current value of system variable:

Command: _SOLIDEDIT
Solids editing automatic checking:  SOLIDCHECK=1

0 (zero) = It disables the automatic debugging process of AutoCAD.

_VIEWRES command is another setting that affects the display of circles and arcs only on screen while zooming. Increase its value to 20000. You can see the other settings that I have mentioned above in OPTION settings of AutoCAD (configuration). Aim the mouse cursor into the command window and click the right mouse button, by this way you will get the ability to choose command from the menu.

Hope to see you in another share … Good bye,

Similar Posts

• System variables
• 3D Modeling 13: Getting 3D wireframe from a solid using XEDGES command.
• Lock your user interface with LOCKUI system variable
• Introduction to AutoCAD 2009: 5 - VIEW CUBE
• Managing Visual Styles in Autocad 2007

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3D, 3D Modeling, AutoCAD 2007, Autocad, Hints & Tips