View Full Version : Volumetric lights, feature or bug???

01-27-2005, 03:39 PM
Hello again...
I am working on a rendering of a 1930's street scene and in the process have included a period street light.... thus the problem. I have a single volumetric light inside the globe and an area light there also to generate the shadow of the pole. Puzzled, I created the test file with four lights, left one is narrow cone volumetric, next is a wide cone, third is a stand-in globe with volumetric spotlight inside (no-show???!!!) and the far right is a combination of narrow cone and wide diffuse cone spot light, yes I know that the center is a "blown-out" and suggestions on this are welcomed, however when I go back to the street scene and clone the narrow focus spot, widen it's cone and drop it's intensity, only one light renders???? I am getting tired of waiting for the renders only to see failure. Shouldn't the spot lights generate a pole shadow???? Can't two volumetric lights appear in one place. Turning on Viper is useless, alternatingly showing one or the other depending on when I go into the Volumetric Lights panel and click on the "good, medium, best" choices, then Viper updates the chosen light, "blowing out" the other one.... so it goes, back and forth.... I have attached a scene file and object file if anyone is curious

01-27-2005, 04:44 PM
You have your light set to fall off before they reach the ground. why use shadow maps just use ray... your ray recursion limit should be less then 16 make it 4 or so. Takes some time to know what all those settings do. ;)

01-27-2005, 05:00 PM
And if you stick a light in a pole it will not shine through. :eek: Not to be ugly but ask for help by saying something like " hey what am I doing wrong" not " is this a bug or feature" Really lots to learn - nad young grass hopper one must knwo first that one does not know before one can knwo what one needs to know. Lots of helpfull folk around here lets see your work as you progress.


01-27-2005, 05:11 PM
Turn radiosity off when trying to work thourgh a problem as it will speed things up. Thus those test renders will **much** go quicker. :D

01-27-2005, 05:17 PM
a few setting I toyed with on your scene -

and I think if you have soft edge grater that half of your cone angle you end up with little to no light - kinda softens itself out all together.

01-27-2005, 06:48 PM
Wade, Hello... Thanks for the response and the discussion. I have attached three images for reference, one showing my inclusion of the settings that you had offered and a second showing some of the results/questions... I went to NVidia and made sure that my video drivers were updated before these reenders just in case...
Note that the FPrime shows two of the shadows but not the central one and the Viper shows none of the volumetrics, tho it will occassionally if I fiddle with the settings enough, but only one (thus the question, "is this a feature or a bug"), and finally a test render with more weirdness than ever before. Any idea about the large rings???? I have also included an earlier render of the streetlamp scene when I had it first working. My intent was to have a more narrow spot straightdown and then an overlapped softer diffuse going out, both in the same place, with the shadow of the pole. Clearly this "young grass hoper" has much to learn, but usually I am not so befuddled and getting worse for the effort???? Thank you again for any insight. I included the scene file again if any further understanding is possible.

01-27-2005, 07:16 PM
Ok I think your light is up in the pole and can't see out the end of it, nor through the globe. You can tell an oject or light exclude an object so it can see through it so as to render the volumetic stuff, but then it will not cast a shadow. Try working with the middle light - bring it down out of the globe or pole. It should cast a shadow. Now play some with the obeject or light properties. something like exclude light or exclude object.

Again the volumetric effect and light will stop when they hit an object like the inside of the light globe. :)

Hope this makes some sense.


01-27-2005, 07:20 PM
Ok agian you do need to move you light down out of the end of the pole, then have the light exclude the globe. your light will then go through the globe, but the pole will be seen adn cast a shade as wanted. :) :cool:

01-27-2005, 07:24 PM
rings could be have no soft edge at all or an Fprime thingy not sure that Fprime is billed as working iwth Volumentircs or not. :confused:

01-27-2005, 07:35 PM
rings have to due with your quality settings being low / your light cone angle being so wide - so crank you quality settings back up on the volumetric panel,

and maybe give your stacked lights a little offset from each other.

Headed to the 24hour fitness for a little Volume reduction see ya another day. 8:35pm Cypress texas time, last one in the studio is me. :o

01-27-2005, 11:43 PM
Wade, Thank you for your thoughtful comments, they were very helpful to point me in the right direction. I have attached a version with the building and the street to let you see how it is planned to be rendered. I went back and "excluded" the globe and adjusted the settings of the lights.
Separate question for you and others.... would HDInstance be useful for the "florets" at the bottom of the fence and going up the railing. I am concerned about the polygon count going up and these seem good candidates???? Anybody???
Crits and comments are always welcome.

01-28-2005, 09:42 AM
I would just hardwire details like that, I have had scenes in the 2 to 3 million ploy count and they render just fine in LW. Now Fprime needs too much ram when you get that high with texture maps. If you plan on a whole city with such details then use clips maps or lower the detail when not "in" camera.