Mantra settings for nice render with soft shadows!

[chrsmith]

Hi all,

I've used Houdini for years, and every time I try to make a mantra ROP that will give me nice renders with soft shadows I give up. I play around with all kinds of settings and always end up with slow renders with alot of noise. Why is this so difficult?

Can someone tell me which settings to set to get a "pretty" render? Assume I'm not using anything funky like atmospherics or fluids, just objects, some with transparency with a couple of lights. I assume I need to set the main light casting the shadow to have "Depth Map Shadows", since that's the only one with a "Shadow Softness" parameter. What setting do I change to get rid of all the noise?

Thanks!

Christine

Edited July 8, 2011 by chrsmith

[brianburke]

big soft area lights and pbr.

all raytrace everything.

(just my 2c)

[bhaveshpandey]

I tried rendering water surface with both Gaussian and Catmull-Rom filters and I loved the latter ones. They are crisp and to an extent faster than gaussian (though they introduce noise in the render, which could be removed/reduced using a higher pixel sampling)

I suspect this will not really be of any direct help..but it cant hurt to keep in mind.

have a look at jeff's old school blog (it comes in very handy as far as rendering is concerned):

quantization filters

Edited July 8, 2011 by bhaveshpandey

[Jason]

How are you wanting to light your scene? From environment (HDR) lights? CG point/spot lights? Are you going for realism? Do you have an example scene for us?

Once you know where to look, it's really easy. We can show you by changing a scene you're working on most effectively, I think.

[chrsmith]

Getting there! Got an area light with a big area size and pbr.

My shadows are coming out really dark though, and Shadow Intensity was having no effect, even if I put it down to 0. Adding another light with no shadow lightens the shadows somewhat, but not enough where the object casting a shadow is really close to another object...Ambient light isn't helping either....

[chrsmith]

How are you wanting to light your scene? From environment (HDR) lights? CG point/spot lights? Are you going for realism? Do you have an example scene for us?

Once you know where to look, it's really easy. We can show you by changing a scene you're working on most effectively, I think.

I'm trying to use the basic built-in lights, currently set to area light with a couple of point lights as fillers with no shadows. It's almost 11PM and I need to get home. Leaving a render over the weekend (I'm off Friday) that may be ok, but on Monday want to play a bit more. I really don't want area too dark. Spent the last couple of hours doing render after render trying to lighten the dark shadows.

I'll be back!

[Jason]

I'm sure there are settings which will work for you -- we'll get 'em for ya.

[edward]

Spent the last couple of hours doing render after render trying to lighten the dark shadows.

Are you viewing your images with gamma correction? This is esp important for PBR renders.

[Jason]

Are you viewing your images with gamma correction? This is esp important for PBR renders.

If you are rendering into gamma 2.2 colorspace, be sure to set your Color Space in your ROP to gamma 2.2, so that the noise thresholds are in the right color space.

Lightening shadows in an environment? Up your Diffuse Limit. Perhaps add an Indirect Light (which you can boost, at your own risk).

[chrsmith]

Thanks for your help! Back from a long weekend and ready to pull my hair out again. The render over the weekend is unusable. Still a little noisy, the shadows aren't soft enough and are too dark in some places. I haven't specified gamma anywhere. Images:

Here's my setup:

Object setup:

I have each object set with a shading quality of 6 under the Dicing tab.

Objects are using "Basic Surface" materials.

Light setup:

1. Area light (dimmer set to 1) with Depth Map Shadows, Shadow Bias 0.05, Shadow Intensity 0.05, Shadow Quality 10, Shadow Softness 0.757, Shadow Blur 2.

Auto-Generate Shadow Map with Resolution of 1024x1024, Pixel Samples 11

2. Area point light from the bottom, dimmer set to 0.2, no shadows

3. Point light shining on the back of the structure, dimmer set to 0.5, no shadows

4. Point light shining on the front of the structure, dimmer set to 0.4, no shadows

So I would think I have enough lights, but as many lights as I've added, it's still coming out with dark shadows.

I thought that Shadow Intensity would be the main factor, but I have it set really low (0.05). It looks the same whether low or high.

Render setup (settings that I've changed from default)

command: mantra -s 3

Pixel Samples 13

Rendering Engine: Physically Based Rendering, Tile size 32

Anything jumping out at you?

[chrsmith]

Perhaps someone can send me a hip file with a ROP and lights that they may have used in production where they needed soft shadows? That may be easier than dissecting my problem. (I can take Houdini 9-10)

Thanks!

[edward]

Are you looking for a render which looks more like below? It is gamma corrected with 2.2.

[anim]

any reason why using Depth Map Shadows with area light?

if you really want soft shadows and not just blurred map use raytrace shadows with area light

then size of the area light and distance from object will control the softness

if you are looking for realistic renders, use physically correct attenuation and 2.2 gamma as you have already been told

[chrsmith]

Are you looking for a render which looks more like below? It is gamma corrected with 2.2.

I guess so, kinda. Are you suggesting that I dim all the lights to lower than I want or darken the materials to darker than I want, and then blow it out with gamma correction? I doubt if that's what people do normally. I'd really rather light it "correctly" using industry standards. I guess it's an interesting idea for a fallback option.

It seems to me that I'm simply missing something needed to just get the "Shadow Intensity" parameter to work.

Thanks!

[chrsmith]

any reason why using Depth Map Shadows with area light?

if you really want soft shadows and not just blurred map use raytrace shadows with area light

then size of the area light and distance from object will control the softness

if you are looking for realistic renders, use physically correct attenuation and 2.2 gamma as you have already been told

I was using Depth Map Shadows because it was the only one with the option for "Shadow Softness" I'll try Raytraced Shadows. Where do I set gamma to 2.2?

[chrsmith]

Looks like I'm getting somewhere now! When I switched to raytraced shadows I didn't see a difference at first. (I had tried raytrace before when Brian said raytrace everything), but I see now that PBR was the culprit. I changed from PBR render to Raytracing Engine. Now seeing a definite affect of "Shadow Intensity". I still can't find a gamma setting anywhere, but it looks like I don't need it. A few tweaks and I think I'm in business. This will change the way I render from now on.

For years I've done micropolygon rendering and had crisp shadows. In some instances, I'd render the shadows separately and blur them, though it wasn't quite right. Every time I've tried to get a render with soft shadows I'd give up R&D due to time constraints. This will definitely improve the quality of my work.

Thank you all for your suggestions!

[edward]

I guess so, kinda. Are you suggesting that I dim all the lights to lower than I want or darken the materials to darker than I want, and then blow it out with gamma correction? I doubt if that's what people do normally. I'd really rather light it "correctly" using industry standards. I guess it's an interesting idea for a fallback option.

I thought "linear workflow" is sort of already standard in the film industry? Of course, I'm hardly an authority on this topic.

Now, actually the pipeline is more of: sRGB -> linear -> sRGB. (where gamma 2.2 correction approximates sRGB). Magnus mentions this here:

http://www.sidefx.co...=20&revdate=off

I wish I could find a good tutorial on gamma correction but if you google for "linear lighting workflow", you'll get plenty of hits. As a first step, try some of these pages (albeit tailored for other 3D packages):

http://www.mintviz.c...flow-explained/

http://softimage.wiki.softimage.com/index.php/Gamma,_Linear_Color_Space_and_HDR

I hope this clears some of it up. The "gamma correction" slider is pictured in the attached image. As for the setting that Jason mentioned, you have to add it via the "Edit Rendering Parameters" dialog.

[chrsmith]

Thanks, Edward, I found the gamma parameter so I can now render with it. I'm a total doofus about the gamma/monitor history stuff. Our resident wiz says our monitors are calibrated.

Update on my progress:

Well, I was quite excited about the area light and a few renders looked really nice. I got 2 minute render times when the radar was small, but then I got a 1 hour 43 minute render time for the frames where the radar takes up the whole screen. I found out how to do global illumination a la this video: http://www.youtube.com/watch?v=1z7g8Y5iylw. It definitely has the "pretty" factor I was looking for, although I don't get the benefit of a directional shadow. The 1.43 frame takes 20 minutes with GI. (We don't have a render farm....yet another reason why we haven't spent much time on raytracing and shadows, because we just don't have the processing power.) So now I'm trying to decide between the area light I've gotten to work with your help and a global illumination light.

I'm also getting some weird problems with objects that have opacity set at 0 and fading up (Basic Surfaces). It's rendering the specular highlights of these objects that I shouldn't see at all. I might end up doing this with GI if I can't get the speed up and fix that ghost problem.