Greetings, all...

I'm in the process of creating some 3D models for my undergrad thesis project. I have a pretty good grasp on the actual modeling aspect (my geometry is fairly straightforward - no weird blobs or anything), but I'm struggling with the materials and lighting.

Right now I'm doing all the modeling and rendering in AutoCAD 2009, mainly because I'm comfortable with the interface, I don't have to worry about file translation issues, and I don't have the time to become proficient at 3DS Max or Rhino.

Here are my results to date... My project involves developing a rapid transit system, so these are interior shots of a subway train I recently modeled.

The materials are looking okay, but I was having trouble with the lighting, as AutoCAD's default fluorescent strip lights don't put out nearly as much light as you'd normally expect in real life:



However, I compensated by doubling the number of light sources and drastically beefing up the output. From this point on it's pretty much a matter of trial-and-error to get the right light levels. Here, it's probably a little too washed-out, but that can be adjusted.

Also, there's one material that stubbornly refuses to render: The seat backs are supposed to be the same stainless steel as the grab bars, but for some reason they're not showing up as such, no matter how I change the settings. Each seat is a block that contains the stainless steel seat back and blue fabric. This rendering is 90% there, IMO, but it was just a draft at a fairly low resolution.



Yesterday, I decided to render the same scene at a much higher resolution. However, none of my materials are now rendering at all. They still appear in the materials dialogue box, and the MATERIALATTACH command still shows them as being associated with the correct layers, but nothing is showing up. The render settings are also set to render materials, but nothing is coming through.



Help!

Some will probably suggest importing the scene into 3DS Max and doing my renderings there, but I'm trying to keep everything within AutoCAD if at all possible for a number of reasons.

I'm using the subway car interior as sort of a guinea pig... Once I figure out how to get the results I want here, I'm hoping to apply those lessons to the actual stations that are the main focus of my project.

Thanks....

I just noticed that a couple of the seat cushions are showing the correct material in the last rendering above, but not all of them, and none of the other materials are showing. Bizarre.

The seat cushions are also supposed to be more of a navy blue instead of the baby blue as shown, but I'm trying not to lower the overall light levels in the scene.

I do not know the ACAD rendering interface at all, but it might be a "camera" issue rather than a lighting issue - is there an exposure setting that can be adjusted? In the old fashioned rendering program I use there is also a setting for ambient light, which is faking it but can make the image more perceptually correct.

keep it dark then take it into photoshop and tweek it in there.... might be easier

Thanks for the advice so far... Keep it coming.

I tried using the dedicated render workstation my office, and for some reason all the materials are showing up correctly when I use that computer instead of my own, despite having made no changes to the drawing. Very strange.

I was hoping to show the results of that rendering, but Windows spontaneously decided to update itself and reboot at 3 AM while the rendering was still in process. Thanks a lot, Vista.

in other programs I'm familiar with, surfaces won't render if they're normals are flipped the wrong way....might be one of your problems

Definitely a RAM issue (does the map come back at a lower resolution?). how big is the map you're trying to use (ACAD is probably loading each copy into memory)? try swapping out a lower-res version for the seats further away from the camera and use the "standard" version for the ones close to the camera.

the lighting problem may be a scene scale issue--is everything at "real" scale?

Interiors are tricky especially when using GI; unfortunately ACAD is using a hobbled version of mental ray. Try deleting all lights and start off with just a skylight (especially if you're model is "open ended", meaning the camera is not actually in an enclosed space). then start adding the key lights and other fills. lighting color can help too (high intensity blues are perceived as less bright than the yellow end of the spectrum).

the other thing that may be affecting the model (that LML has suggested) is how you've drawn the profiles used to create the extrusions/sweeps: the older versions of ACAD were fairly dumb and required the user to always draw (everything) clockwise or counter-clockwise else it would not be able to tell which side of the solid was the outside (the normals on some geometry would end up flipped and render black)