Tips for rendering/ray tracing dark objects

[mcgyvr]

My goal is to get it so that I can just turn on realistic visual style and ray tracing and be able to get usable screen shots for product datasheets/marketing material without having to resort to rendering in studio. (If possible and I think it should be) All my products feature a black powdercoated enclosure (think DVD player shape/size). When I enable ray tracing all I basically see is a black blob with no good definition between surfaces,etc.. (See attached image) I'm assuming now that I need to do 2 things #1 increase/modify lighting and #2 modify the colors in the style library to work better. For that black color in the style editor I basically have all 4 colors (ambient/diffuse/specular/emissive) set to black. Is there something I should do to allow "more realistic" colors instead of just all color options set as black? I think this is where I need to help/pointers because I just don't think all black is correct. But I really don't know which one does what and why. Any other tips would be greatly appreciated. I've gotten very decent renders from studio that worked just fine in the past but I've got oohh roughly 400+ screenshots that are needed now for new products. (busy year for me) I can play around with settings till I'm blue in the face but I was just looking for tips to have a decent baseline to start with.

[cwhetten]

I haven't played with the ray tracing much, but you definitely don't want to set up your black color style the way you described.  I have attached the Black color style that comes out of the box with Inventor.  It has diffuse and specular elements that are not set all the way to black.  I have had trouble with the default black color in the past so I use one that I created (also attached) that is "almost" black (the ambient is not quite black, just a REALLY dark gray).

As far as the lighting elements of each color style here's a quick description:

Specular -- Light directly reflected from a light source.  If your object is a mirror, this specular light would show up as a perfect reflection of the light source.  As the reflectivity of your object decreases, the light scatters more and more, in effect "smearing out" the reflection of the light source.  The color of the specular light typically matches the color of your light source.  (It is usually white, but you can get some interesting effects by using other colors).  If your object is completely matte (no reflectivity other than diffuse reflection), then set this color to be something dark, or even black.

Diffuse -- Light from a source that, instead of being directly reflected, is scattered in many directions.  This tends to light up areas of your object that are not in a direct reflection path between the light source and the eye.  However, this won't light up an area of your object that is in shadow.  The color of this light shows the color of your object.

Ambient light -- Light from no source in particular, just coming from every direction (like blue light from the sky).  This will light up your entire object, even areas that are in shadow of the light source responsible for the specular and diffuse elements.  The color of this light shows the color of your object, but can also be affected by the color of the source (like blue light from the sky, for instance, or an object sitting in a room with bright red walls).

Emissive -- Light from within the object itself (as in a glowing hot metal, or a light bulb).  Unless your object is supposed to look like it is glowing, this is usually set to black.  This will tend to brighten every area of your object, and reduce shadow.  This setting is quite powerful.  Even a very dark gray will have a drastic effect on the color of your object.

Hopefully this helps.

-cwhetten

[mcgyvr]

Thanks for those descriptions.. I'm having excellent luck just forgetting about those 4 color choices and assigning a "realistic appearance" for each color. Its amazing how that took if from a black blob to an almost photographic representation in just a few clicks.. I'm still messing with everything but that seems to be the way to go. Tips still welcome.

Here is what the same assembly with the realistic materials applied.. (And for giggles placed it on the dry salt bed)

If you saw my products in person you would swear this image is a picture. Its amazing...

[cwhetten]

Wow!!  What a difference!  Is that image a screenshot of the ray tracing, or is it a studio render?

[mcgyvr]

Just a screenshot of raytracing turned on.. amazing isn't it.. and I noticed I took the screen snip before it was even finished.

Studio is now dead to me..

[sam_m]

great work mate.

just thought I'd chip in in case users read this in future...  a LOT of the supplied default colours are pretty bad for rendering - most of the reflective styles (mainly metals) have a non-black emissive - this is wrong.  No matter how shiny a ball bearing is, it doesn't start to give off light, but that's how it's setup   Also, some of the realistic colours in 2011 are bad/bugged and incorrectly shiny (rubber, brick, etc), so don't just assume what's there out of the box is the best (dunno if they've been fixed in 2012.)

so, 1st thing, strip out all those emissives (except for materials that actually give off light, eg molten metal, glowing LEDs, Green Meteorite etc).

I've also had great results by using the bump-map settings.  In reality nothing in smooth, everything has a texture, so why shouldn't your materials???  Adding a slight bump-map can break up the surfaces from their clinical perfect shapes and aid to the reality of the part.

Following from the last - most renders look too perfect and thus instantly look fake (eg all screws in line and bob on 90degrees, etc.) so try and add "errors" and mess to the scene. 

use perspective viewpoint, instead of orthographic, and use shift + ctrl and mouse-wheel to lower the effect to something more realistic and less fish-eye.

[mcgyvr]

excellent tips sam. Never knew about the crtl+shift+mouse wheel trick.

Bill Bogan from Autodesk gave me some excellent tips in an email too. Here is one thing he wrote that really made a huge difference with just one change. Here is what he wrote talking about all my colors using black..

"I changed only one component, Specular, to use “White”. Think of specular as the highlight you see on something. It is the light vectoring rom the object to your eye.

That coupled with the shininess setting control the highlight you see. Shininess controls the diameter of the specular highlight."

and his comments about the color options

"Ambient is the light influence in the immediate area. E.g. if I am in a restaurant, the lighting might be more yellowish and subdued. So, I would set the value to a darker yellow to show that influence.

Diffuse is the color reflected when light hits an object. The color reflects in all directions. So, in the image above, the black is the diffuse color, white is the specular color and these blend to give me the gray tones – interpreted by our eyes as specular highlights.

Emissive is the color of light the object emits."

[Anonymous]

This information is really great for me right now. I have a project that has all black parts. I am not sure how to save the "almost black" so that I can add it to my project. Could you help me out with this?

[RogerCamp]

Studio has the option to have transparent background, which is useful in some cases.