Speed Issues (contours & aerial photos)

[admin.60978]

We are beginning to do some large jobs involving a large set of high resolution aerial photos and 2ft contours (all georeferenced). Currently the photos are inserted as raster images (referenced) and the contours are inserted as blocks or exploded and trimmed.

We have fairly good hardware (I thought) -- Athlon64 3400+, 1GB RAM, Quadro video card (can't remember the model #) -- but the file is incredibly slow to work with. Panning is not bad but zooming can take a while as AutoCAD keeps loading and processing the raster images. Saving takes a long time, as does opening the files.

The dwg files are ~100-200MB and the rasters are rather large as well.

Is there anything we can do to increase the efficiency of AutoCAD? Is there another AutoDesk product that would process these types of files more efficiently? The contours seem to make things take especially long--there are so many points.

Note: I'm the computer administrator, not the CAD technician, so I may not sound too savvy on these issues.

[Mike.Perry]

Hi

Have a browse of the following thread -

Complete slow down of CAD

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Give the following Technical Documents from the Autodesk Knowledge Base a read -

ID: TS65093 - Use Windows® tools to evaluate system performance

ID: TS18145 - Troubleshooting problems relating to insufficient system resources in Microsoft® Windows®

ID: TS79895 - Slow performance and random crashes with multiple attached image files

ID: TS14213 - Making raster images visible while panning and zooming

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Have you experimented by moving everything locally (including drawing files & raster images) so AutoCAD does not need / rely on anything from the Network. Performing such an exercise should determine if the Network is causing or at least contributing (in a major way) to the issue / problem.

Have a good one, Mike

[admin.60978]

Thanks for this tips Mike. I have tried most of them already, but some of them were new and seem helpful. The rasters that we are using are rather necessary during pan/zoom and I realize turning them off would greatly save on performance, but unfortunately it doesn't look like that is an option. It would be great if there was some sort of "low res rasters during pan/zoom" option.

All of the rasters and contours are on local disks for the main people using them.

Another option that I'm working on is reducing the number of vertices in the contours. Each contour file has ~450,000 vertices and often we use 4-6 of the contour files in each drawing. That seems to be the main slowdown. I found a script on Cadalyst that seems to use a decent algorithm to reduce the number of points on the polylines (I realize this decreases accuracy somewhat).

One of the articles you pointed me to mentioned using WBLOCK to resave the drawing as it rewrites the entire database. Could that really help? If so I could do that to all of the contour files with a simple script.

[Mike.Perry]

Hi

The rasters that we are using are rather necessary during pan/zoom and I realize turning them off would greatly save on performance, but unfortunately it doesn't look like that is an option. It would be great if there was some sort of "low res rasters during pan/zoom" option.

Take a look at system variable TSDISPLAY.

All of the rasters and contours are on local disks for the main people using them.

What about the AutoCAD Support files etc?

One of the articles you pointed me to mentioned using WBLOCK to resave the drawing as it rewrites the entire database. Could that really help? If so I could do that to all of the contour files with a simple script.

The WBLOCK method is one-way of reducing file size to it's minimum (approx).

Have a good one, Mike

[mjfarrell]

I would suggest that you look at using MAP to limit the size of the
loaded data-set. Additionally MAP has settings to reserve memory for
Raster images.
Look at your Land Desktop settings for Weeding the Contour vertice information.
Also with Land the contours and points do not need to be in the drawing as
they are available through the projects database.

[Coolmo]

Check your LTSCALE to see if it's at a low setting. When we have contours from a GIS block set to a linetype of "dashed" and the LTSCALE is set to 1, the regen takes forever because it has to figure out all of those billions of breaks in the polylines. Set the LTSCALE to something like 50 or 100 and see if that makes a difference. Also, we sometimes use images in our drawings and I always open the image up in photoshop or equivalent program first to decrease its size and make it a different format other than tif. This always works for me and there's little if any quality lost.

[tlewald]

It sounds like compressing your images to .sid format may help a GREAT deal, since it reduce your image by approximately 1/10 of it's current size without any major effect on the quality.


Sounds to me like this is the major source of your computer dragging so heavily. I deal with this type of issue on a daily basis and in my opinion, SIDS are the ONLY way to fly!

If you're not familar with this type of format, check out this website: http://www.lizardtech.com/

[admin.60978]

Thank you for all your help (everyone). Many of your suggestions increased our performance. I think we may be buying Raster Design and switching to .sid files for compression. The main thing that helped was reducing vertices and compressing images.