Walk About BG Image Problems

[Joel Spack]

Frequently I am asked to set up a render on a photographic background and the ability to insert an image into the walkabout window makes setting up said renders much easier than it would be otherwise.  The problem is, the Walkabout BG image hardly ever works, and when it does it works quite poorly.  When selecting an image I frequently get the "Unhandled exception has occurred in a component in your application. . . . Attempted to read or write protected memory.  This is often an indication that other memory is corrupt."  I've run several ram testing programs which lead me to believe that my ram is fine, and this happens on every computer that I've tried it on in my office.  When this error occurs there will be no walkabout BG image displayed.  The other possibility is that it will (albeit rarely) allow me to use a BG image but then the manipulation of the camera slows to a grinding halt (my guess is the walkabout window switches from 30ish FPS to 0.2 FPS with the addition of a BG image).

 

Does this happen to anyone else?  It is incredibly frustrating :(

 

Here are my machine specs, if necessary.

 

Core i5 750

Radeon 5770

8 GB RAM

Windows 7 Professional 64

Autocad 2009 Vanilla

[Roy Hirshkowitz]

No reports on my end.  First--make sure you've got the current build of nXt (271).

 

AutoCAD is running the WalkAbout display-- it's very possible that a high-res background photo is killing the performance.  It's also possible that the source of the crashes are on the AutoCAD end.  You could try using a low-res version of the photo to do your view manipulation.  Then switch to a high-res one for rendering (or better yet, composite the photo in later using an alpha channel.)

 

If you've got something that crashes consistently I'm very interested.  I'll need all the files required to reproduce, probably just the image and the dwg.  If you're willing, zip it up and upload it.

 

BTW an error like this is almost never a hardware problem.  It is the most common way a program crashes.

[Joel Spack]

Thanks for the clarification about the nature of the error, I appreciate knowing that it most likely isn't an issue with my PC lol.

 

I am currently using 270, but this has been happening almost as long as I've been using NXT (either the end of 2009 or early 2010).  When I come back in the office on Monday I'll install 271 and attempt to recreate the error.

 

I always use a significantly reduced resolution image for walkabout BG images, something around 160,000 pixels total (400x400, 800x200, etc), and the reduced size.  Then I render somewhere around 2500px wide for most jobs.  Size of the WA BG image seems to have no correlation (that I have noticed) to the likelihood of success or failure, I've had tiny images fail and surprisingly large images succeed.

 

[Roy Hirshkowitz]

Like I said, I'm very interested if you come up with a reproducible crash.  The image res recommendation had more to do with the performance problem you noticed.  No clue what the crash is.

[Ros. Riha]

here is my recipe - I present it in hope somebody would improve it:

1. Insert the photograph of the neighbourhood into paperspace
2. In the paperspace, draw an outline of existing buildings (or other elements) you will be able to create in 3D as a part of your model later. Unload the bitmap image, leave only outlines.
3. Create the model (as simple as possible - just boxes) of existing buildings (or other elements) you decided to outline in the step above. Put them to separate layer.
4. Create a viewport in paperspace and isolate the abovementioned layer there.
5. Match the outline with the simple model of the corresponding neighbourood - use any commands that suit you. Knowing the exact location where a shot has been taken from alway helps.
6. Turn on appropriate layers to show only your design, hit render.
7. Mix in Photoshop

[Miguel Tano Adanes]

Hi Ros,

me too have to render often with background images. I make it like Roy suggested:

- make a perfect copy of the background image to use but in very low res and possibly b/w. It is very important the dimensions need to be the same (ie. 1600x1200 or whatever) and of course the final render need to be the same, too.

- match the bg with your model (wireframe) in walkabout view, using a very low increments and the same focal lenght of the camera  which shot the picture (you can see the jpg properties to fix it)

- I use low res and b/w background images because you can easier see your model, as I use many colours for different layers.

- render the view without the low res bg image and save it with alpha channel OR render the view with hi-res bg image. This second option requires much memory and in case of post production could cause difficulties in setting up brightness or contrast or whatever.