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View Full Version : Horrible renders...what am I doing wrong for this effect?



Algae998
09-15-2007, 11:10 PM
Hello all,

Algae998
09-15-2007, 11:18 PM
(oops, hit submit without the info!)

I had recently posted a thread on how to achieve a spotlight effect where the beams of light are visably shooting off into the air. I began testing this on another model, inside a box with some gears. The objective was to have the spotlight shoot light skywards, illuminating the gears and having light beams visable. It was suggested that I use a spotlight, with volumetrics enabled. These are my results...what went wrong? everything is washed out, too illuminated and the light is very grainy.
(this render is 512x384 with an AA of 1 or 2)
Any ideas?

jameswillmott
09-16-2007, 12:55 AM
Quality of the volumetric light is too low? Try increasing it... can you post content for us to dissect?

Algae998
09-16-2007, 01:31 AM
This picture is prior to my previous posted picture (I had saved this scene and tried to get a more dynamic light setup and resulted with the pic in the first post). This one is a lot better than some of the others but Im not sure what options do what, so I kind of walk blindly, testing the various settings.

For this scene I had a spotlight (hidden within the box pointed upwards) and an area light (outside) to help luminate the exterior. I believe the area light helped a bit. Anyway, here are some screenshots of the Render Globals, Light and Camera menus. For this type of bright spotlight in a foggy atmosphere look, do I have some of the settings way off? I know thats a difficult question to ask since theres so much variation, but what the heck.

(I was too frustrated with the horrible render to have saved the other scene to get the info from)

G M D THREE
09-16-2007, 05:07 AM
I always render volumetric's in a separate pass on there own, making all object mated black. Its way easier to control it in a comp. In your case I would play with the volumetric values around and also try moving the light a bit in case something is blocking it. Sometimes all that wont help as it will be physically correct but wont look good. You can get creative and have the light ignore the model and juts project a texture true it with a similar stencil like design, like your gears.

If you are not in a rush with it and have time you can stop by at the NY LW user group meeting this Thursday the 20th http://nyclightwave.com
If you come 30min before we start and can tweak your scene and make go bling.

///

Algae998
09-16-2007, 08:30 AM
Id love to go to the LW group meeting, or even be a part of it, but Im not close to NYC at all. I live allll the way over in the bum section: Western NY, near Buffalo. Plus I have classes all this week.

So for rendering in multiple passes...are you talking of rendering two frames? One of the gear/box with the correct lighting and then another of just the light streaks using the the rest as a black matte? Not too sure how to do that exactly but Ill have to give it a whirl, haha.

Is the noise and grain of the spotlight (first horrible posted picture) normal or do I have quality settings off (such as the the lights Good, Medium, Low quality)? In the light view I did try and make sure there wasnt too much in the way of the light's path, since I could see thru the gears.

Im hoping I can find a setting that will eliminate the blockiness, and edge repeating of the spotlight's beam.
Thanks for the tips!

G M D THREE
09-16-2007, 07:07 PM
Yep you render two images one a beauty pass of the model with nice lighting and a second pass where you select all your objects and under properties render tab check matte object and make sure color is set to black, turn the volumetric light on, set the quality to best. Than in Photoshop put the second render with volumetric light above the beauty pass and select screen mode. This way you can change the levels of the light to make it stringer or even slightly blur it even duplicate to make it even more intense!

///

Algae998
09-16-2007, 07:51 PM
Sa-weet, Ill give that a shot. Thanks for the tips!

Algae998
09-16-2007, 10:25 PM
I decided to start fresh on a new model. I whipped this model up and tossed a point light inside the hallow cube with volumetrics. By this point, my wall is pretty well dented and my head hurts. I tried rendering just the model then just the light's volumetrics and combining them in photoshop with both models. The problem is that the light is so harsh and blotchy that it makes it difficult to work with and inprobable to get the desired result. I tried to duplicate the light layer (in photoshop) and blur it since it was even more noticeable at that point, but the results were almost worse...if you can imagine haha.

I just need a way of smoooothing out that light and it will be all good.
Could the reflectiveness of the object's surface be causing the harsh light lines? Thatd bite if it is becuase Im looking for a very metallic surface.

G M D THREE
09-17-2007, 04:23 AM
Ok here we go. Set your seatings to BEST. It will take 3 times longer but it will look better.

I used some Radial Blur in Psd, with zoom mode set in the center of the light and than payed with some color gradient with overlay mode.

///

Algae998
09-17-2007, 01:21 PM
Thats more of what I have been aiming for, haha :bowdown:
In the Volumetrics options, did you have the check box checked for "opacity casts shadow"? I couldnt tell in that screenshot.

So if I understand this right a low quailty setting for the light will leave a very harsh and consistent beam, where as the best setting smooths it out. Would a hight pass of AA (5 or so) help add to the smoothing, or does that primarily work only on the model's surface?

Algae998
09-17-2007, 07:22 PM
Finally got it! Took nearly two hours to render but this is what I was looking for. I used lens blur in photoshop instead, which looked a little more focused on the lightbeams. Thanks for the help!!!