View Full Version : Rendering question pls read thanx

11-09-2005, 12:56 AM
I am about to render a machine I have been working on, the surfaces are all metallic. I was wondering about caustics and radiosity. The default in LW sets them at 100 % due to the extreme amount of time it takes to render caustis and radiosity was wondering if anyone had any tips. I honestly dont even know what these two options do. I dont want to have to render too many times to figure the correct setting. I know that one or both is related to bouncing the color of an object on to the surface it is sitting upon(i.e. a yellow cup sits on white table some yellow will reflect on to the table and vise versa). Correct? I have looked ths up in my Inside LW 8 book but it is very general in it discription. Are these options nessary? I want to give it a realistic feel to the object. The attached file is what I want to render for print.
Thank you in advance
sm :D

Captain Obvious
11-09-2005, 01:37 AM
I don't think radiosity or caustics will have a big impact on that image. There is very little for the caustics to hit, and the two spotlights and lack of environment means radiosity is mostly wasted.

Either way, in my experimenting, I've found that interpolated radiosity with the following settings works fairly well in most cases:

Rays per evaluation: 4x12 to 7x21 (higher setting increases quality and time)

Tolerance: 0.5 (lower setting increases render time and will often - but not always - increase quality)

Minimum space evaluation whatever is highly scene/scale dependent. Set it as low as possible, but not too low. If you set it just right, it gives good quality vs time, but if you set it just a tad too low, you'll double your render times

Bounces: don't set it higher than three or four.

Intensity: leave it at 100%.

One thing to remember with interpolated radiosity, however, is that you must render using motion blur and at the very least five anti-aliasing passes.

11-09-2005, 03:10 AM
Thank you for the quick response! If you dont mind me asking what are the differences between radiosity and caustics? Like I said before i think i kinda know what it is but that is a hypothesis in my mind not a fact.
sean :bowdown:

Captain Obvious
11-09-2005, 09:25 AM
Caustics are the effects you get when you aim a spot light on a glass sphere. The "kid-with-magnifying glass-killing-ants" effect, basically. Light changes focus as it passes through refractive materials. Radiosity is the interaction of light between diffuse surfaces. Read more about it here (http://www.siggraph.org/education/materials/HyperGraph/radiosity/overview_1.htm).