PDA

View Full Version : Fast blurred reflections ? Is there a cheat ?



ArtGoblin
04-16-2014, 06:16 AM
I know, this question has probably been asked many times before, but for some reason I'm not having good enough luck in my searches. I'm setting up a clay render to showcase my model, will probably be rendered as a turntable animation possible also close-up slow-pan'ing shots. So I'm liking everything about my current setup. But I really would love to be able to set a reflection blur af about 10 to 15 percent on my material, but without the render hit. Didn't Tobian figure out a cheat to half the rendering of blurred reflections or am I remembering incorrectly ?

Here's an image of the current render (I blurred the environment image to try to make up for not having reflection blur on the material, but it doesn't look to sweet when it starts reflecting itself)

http://i162.photobucket.com/albums/t261/Artgoblin/AssoultRifle_ModelWIP_07_combined.jpg

Danner
04-16-2014, 06:28 AM
For still images you can use a nodal material that uses interpolation on the reflection bluring, like conductor. The interpolation can be noisy when animated so it's best for stills.

ArtGoblin
04-16-2014, 06:35 AM
thanks, good to keep in mind, but I'm seting up an animated modeling-showreel so that doesn't seem like the best trick to use now :/

Svenart
04-16-2014, 06:38 AM
blurred reflections are indeed a small problem in lightwave, but Octane is rendering them very quick :)

Danner
04-16-2014, 07:14 AM
It might not look as realistic, but you could use a spherical map instead of raytraced reflections, and that will be very fast, blured or not.
Another way, would be to do it in post, render the reflection buffer separately and blur it in post, probably too involved for something this simple if you are not used to using passes.

Re-reading your original post I guess you did try spherical maps. I don't find reflection bluring all that slow to be honest. Just keep your ray recursion limit low and shading samples as low as you can before it gets grainy.

ArtGoblin
04-16-2014, 07:20 AM
That's not a bad idea Danner... I'm doing some tests now with dropping the reflection all together, but instead using specular with a very low glossines making it very spread and hopefully mimic a blurred reflection. I don't need it to look realistic, it just needs to look sexy but most importantly I need all the modeling details to pop out becouse I'm only focusing on showing of the bare model, then I'll overlay the wireframes in post.

One idea I have is to try using this plugin (https://www.lightwave3d.com/assets/plugins/entry/lightbitch/) to create a light rig, but only use with specular shading, maybe that's give me the soft clayisg look I'm after

ArtGoblin
04-16-2014, 07:27 AM
blurred reflections are indeed a small problem in lightwave, but Octane is rendering them very quick :) Would love to take Octane out for a test ride, but since this is for school I don't have any budget for it :/ As well as limited time to learn the grips of a new renderer

Dodgy
04-16-2014, 08:57 AM
There's a image filter plug in called reflection blur 1 think which uses the special buffer value1 to blur the reflection by that amount If you're not too worried about accuracy

raw-m
04-16-2014, 09:04 AM
Posting primarily to subscribe but, as Danner says, have you tried it using reflection blur? It seems to be pretty speedy in the last couple of LW updates.

djwaterman
04-16-2014, 10:23 AM
I think you solved it already, for a clay type render to show modelling detail, you don't really need reflection and specular will look very very acceptable.

Greenlaw
04-16-2014, 10:27 AM
Just plus one-ing the above and adding some additional info.

I use Reflection Blur--with optimal settings, it's really not slow at all. Reflection Blur used to be terribly slow but somewhere along the way it got much, much faster. Where is bogs down a render, I've found, is in very large complex scenes with a lot of objects using Reflection Blur--in this case, you will need to pick and choose more carefully where you apply it. As mentioned above, you'll probably want to reduce the Ray Recursion Level. The default is 16, which I find is way too high for most situations and can increase your render times significantly. I usually drop it down to 6 or 4, and may go as low as 3 or 2 if I can get away with it. Normally, I just leave it at 6 and forget about it until I see a problem (either in quality or render time.) When I'm not sure, I do a quick test and compare.

I've also rendered reflections as a separate comp element and blurred it in post but I usually save that method for special cases.

G.

allabulle
04-16-2014, 01:44 PM
An old trick, if one can call it that, is to add specular only lights, with colour. Or a Dome light with an image (blurred or not) to affect the specular. It's a way to add hue variation to the specular mimicking the effect of a blurred reflection. It's just another solution. I don't find blurred reflections that slow anymore for scenes like this one either.

ArtGoblin
04-16-2014, 02:16 PM
An old trick, if one can call it that, is to add specular only lights, with colour. Or a Dome light with an image (blurred or not) to affect the specular. It's a way to add hue variation to the specular mimicking the effect of a blurred reflection. It's just another solution. I don't find blurred reflections that slow anymore for scenes like this one either.

Mmmm... think I might just try that... using Lightbitch scripts to create all the lights so they'll correspond with the HDRI environment, then set them all to be specular only.

Here's what I got with using the specular hits from the 3point lighting. I think it is very close to what I want.


http://vimeo.com/92166569
You'll have to view it full screen to see the wires, they are so fine in thickness


Thank you all for your comments and suggestions. Alltough I think I'm fixed on using a spread out specular hit instead of actually blurring reflecions I think I'll have to play a little bit with all the different suggestions later, it's always good to have some mixed bag of tricks in the toolbag :D

Ohh.. and yes I agree that reflection blurring in current LW version is a lot better and faster than it used to be. It's only that I'm extreemely picky about the render times for this project right now, otherwise it wouldn't be a big deal. Render times now are about 1 and a half minute up to maybe 4 - 5 minutes, depending on the details on screen for each frame.

IRML
04-16-2014, 02:28 PM
blurry reflection itself is pretty fast these days if you're not doing an interior

I think tehbian's cheat was to set the radiosity pre-pass to not have reflections, which speeds up GI calculation and therefore render time

I have in the past done a cheat where the reflection blur is set to 0 after the first bounce, which also helps render time with very little visual difference

IRML
04-16-2014, 02:32 PM
I can tell you another cheat I came up with, I call it reflection occluded specular, it may not be to everyone's tastes

you do your lightbitch setup without ray trace shadows, then you do a separate reflection only pass - black object, no diffuse or lighting just reflections, white background, 1 recursion, multiply that over the spec buffer of the first render

it's slower than just spec, but can be faster than full reflections, with the visual result also somewhere in between those two

Tobian
04-16-2014, 04:30 PM
Yeah my cheat was to use nodal trickery to disable the reflection during the radiosity prepass to save a lot of time. You can also reduce the reflection blur amount to nothing on n bounces, using the same trick, however I found that it didn't make that much of a difference on the render speed, as the extra processing slowed it down to the point it was negligable. For something like this, the first hack is usually the best method. For optimal speeds I usually use Delta, with a Schlicks approximation node plugged in, which has the hack built in.

erikals
04-16-2014, 04:58 PM
Tobian, how much time is saved on this?

For optimal speeds I usually use Delta, with a Schlicks approximation node plugged in, which has the hack built in.

Tobian
04-16-2014, 05:04 PM
I can't say for certain, but it is faster. It's entirely related to the scene complexity.

ArtGoblin
04-16-2014, 05:14 PM
hmmmm... has anyone tried this one ? http://rainybrain.org/?page_id=152

spherical
04-16-2014, 05:24 PM
That looks pretty useful. Gonna give it a go.

erikals
04-16-2014, 05:39 PM
There's a image filter plug in called reflection blur 1 think which uses the special buffer value1 to blur the reflection by that amount If you're not too worried about accuracy

interesting, it leaves a shadow around the objects though...

(subnote, forgot to turn on reflection 60 and diffuse 40 in the .zip attachment...)

Tobian
04-16-2014, 06:04 PM
Yeah that plugin doesn't give good results, because it's only screenspace, and it doesn't compensate for boundaries like that, or indeed adjacent same surface depth issues.