View Full Version : Shadow problem - Maya freezes

08 August 2004, 12:25 PM
Hi there!

I'm doing a little robot-spider and it has a big headlight as an eye (on the pictures, the legs are hidden). It can make the hole, where the light comes out smaller or bigger, by opening or closing a aperture diaphragm as u can see on "spider2".
As u can see on "spider3", I've put a spotlight into the bot , and made a fog cone for it. on "spider1" u can see that rendered. But If I turn raytracing shadows on for the light, so that the fog doesn't come through the closed part of the diaphragm anymore, Maya freezes and doesn't make any effort on rendering anymore, so I have to close it. If I use deph map shadows I get a nice and very clean result of a shadow of the light, but tthe fog disappears totaly. And If I use some of the mental ray shadows I get a very rubbish render, altough with a very long rendering time and a massiv consumption of RAM, mental ray uses around 2 GB of RAM while rendering, but I've only got 1, so while writing everything on the Harddisk, it's very slow. And in the rest I get just the same problems as with normal shadows. The fog just disappears.

Can U help me on this?

Thanks a lot,


PS: Sorry bad english, I hope I explaind myself understandable...

08 August 2004, 01:12 PM
dude, try changing your mental ray globals, in the memory limits tab set it to about 70% of your system memory, theres a thread about the bsp tree which is an interesting read.I think from memory mental ray uses all available memory, which can cause problems :scream:

Good luck


08 August 2004, 04:15 PM
Thanks for that tip, I put the limit down from 800 to 600, but I've stil got the same problem, that the fog-cone disappears totaly, instead of just being cut outside. And also the render with mental ray just looked bad. I tried production quality and it took around 1 hour to render, bit it still looks bader then a 5-minutes render with maya software.
I'm satisfied with the render of maya software, my primary problem is, that the fog-cone disappears, if I turn shadows on for the spot light.

Thanks for your help,


08 August 2004, 04:18 PM
dude, I totally suck at light fog, maybe a duplicate the light use one for fog and the other for shadows, I dunno I'm guessing here.

Good luck, looking good so far:thumbsup:


08 August 2004, 05:39 PM
The Maya default light fog dont work well with mentalray, you can try to use the volume fog mentalray shader:thumbsup:

check this

08 August 2004, 06:06 PM
Thanks, I know that thread, but I don't really get that thing with these weird shadernodes of mental ray. But as said, I don't want to use mental ray. Here I've postet another picture, I've hidden the Sphere and the cylinder inside, so that the origin of the spotlight and the fog-cone are visible. As you can see, the fog is cut up, where the diaphragm begins. I would like to know, if it isn't possible to configure the fog somehow so, that it just behaves as the light itself. The fog should just mach the current light. How could I manage that, without getting involved into this weird mental ray things :D .

Thanks a lot,


08 August 2004, 06:09 PM
did you tried to use ShadowMaps instead of raytraced shadows?!

08 August 2004, 06:30 PM
yeah on that picture itself I used dephmap shadows. If I try to render with raytrace shadows Maya just freezes after some seconds of rendering, resting at 100% cpu usage. :( I'm sure of that, because while rendering the ram usage changes all the time, but from one moment to another the changing stops, and maya is frozen.
I used these options:
Light Radius: 1.000
Shadow Rays: 1
Ray deph limit: 2
For what exactly are these options good?

08 August 2004, 05:19 PM
Oh c'mon, no idea??? :cry:

08 August 2004, 05:56 PM
You can try to activate decay regions in your light. This will enable you to start and stop your fog in different areas. You can adjust it in you light att ed or if you click on your light and press T you will see a little circular icon. Keep pressing it until you see the blue circles. From this you can move the cirlcle yo adjust where your (light)fog starts and ends. see the attached pic.

08 August 2004, 07:42 PM
Thanks, I'll take a look at that, although I don't think it's what I'm searching for. Now I managed to have such a nice fog coming out of the hole by scaling the fog cone to fit the hole. Could it be, that this standart fog is really jsut a cone, with nothing in it? So that it isn't volumetric? Thats how I explain myselft, that if the edge of the cone is covered by the diaphragm, nothing comes out, instead of a nice fitting shape.
So it seems that I have to use some sort of volumetric fog on that, don't I?

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