exclude from radiosity

[Guest hinyc]

hi~~

I exclude small objects from radiosity calculations by modifying their properties for more quick render. As far as i know, they won't change the rendered image much.

 

but small objects(exclude from radiosity) are all black, when they were rendered after radiosity solution. Other objects (except small objects)in the scene are fine. What's the problem? modifying properties? right click the small object, and check "exclude from radiosity processing" in the radiosity tab. right? Unit scale? I tried every option..

 

Please..help me. waiting for your solution!!

[abicalho]

There are some things you need to think of when excluding objects from Radiosity:

 

- Is there another light that is illuminating this object?

- Which rendering method are you using? Render Direct or Re-Use? When using Re-use, no lights are rendered, and only the radiosity light is used, so any object that's excluded will render black.

 

Hope this helps explain it.

 

Alexander | discreet Quality Engineer

[Guest hinyc]

hi^^ abicalho

 

Thank you for reply..first of all, there is only one light(free area)in my scene. Second of all, of course I used "render direct illumination".

for the test, I made 1 box for room and 2 red sphere(one is excluded from radiosity calculation) and calculated the radiosity. and then rendered the scene. 1 red sphere's black(exclude one)and others(box,another sphere) are fine. hooo~~~OK here's the reference.

 

http://pointa.autodesk.com/local/enu/portal/Articles/article.jsp?articleId=15738

 

See the third paragraph in "Suggestions for Saving Time". She said ".... they won't change the rendered image much (see Figure 1)." but they will.. very much...BLACK!! she's wrong? I don't think so. I don't know what's the problem. Anyway thanks you

 

[ September 05, 2002, 12:15 PM: Message edited by: Joshua ]

[ZepSOFD]

Joshua,

 

((Third, reduce the number of objects for which radiosity is calculated. When you calculate a radiosity solution, Autodesk VIZ software determines how light will bounce off each object to illuminate others near it. If you have a room with numerous small objects, you may want to remove those objects from the radiosity calculation since they won't change the rendered image much (see Figure 1). ))

 

This article is fairly correct, but you must remember that this was written to be a hard and fast rule. There was quite a bit of detail left out for whatever reason probably because the writter assumes a certain amount of knowledge from the reader. I think the context from the above quote (which I believe you are referring to) is that small objects that would not produce enough light to change the illumination of the scene do not need to be calc'd as part of the radiosity solution.

 

Calculating the radiosity solution is not the same as rendering they are two different processes. So if you exclude from the radiosity side you need to light the object directly during the rendering process. In your example scene you described using an photometric area light, you need to make sure that in the light (right click object/properties) under the radiosity tab you have "Store Direct Illumination in Mesh" unchecked so that it will illuminate your object during the rendering part. Unchecking this will slow down your render, you would be better off just leaving it check.

 

There are faster ways of getting these objects illuminated.

 

One is to use standard lights to illuminate the uncalculated objects using include/exclude of the standard light.

 

Two is to turn off all meshing of the object and just run the rad. sol. on the scene (depending on the scene the overhead may be worth it).

 

Three use self-illuminated materails, not always pretty but it will get the job done quickly.

 

I'm sure there are many, many other ways to acheive the same results, these are just were I like to start building from.

 

Good luck,

 

tom