mental ray interior daylight scene

[Fran]

Hi Everyone,

 

It is time for me to get some feedback on this test scene I'm using to learn mental ray. I had to add diffuse glow in Photoshop for the windows - I can't get a good view from a window yet. I'm working on it though.

 

All comments and suggestions are welcome.

 

 

 

[Francois Yenny]

Hi Fran,

 

First let me say that I've greatly admired the work you showed in previous posts as well as that which can be seen on your web site.

 

This new work is in the same vein, that is very high quality IMHO.

 

Since you mention that you're starting to use MR, and from what I can see you already have a good (great) grasp of it (far better that mine any any case), I have ask for some basic advice:

 

How do you go about setting up a scene like yours as far as lighting? Are you using GI and Final Gather with just an exterior light or have you added non visible interior light sources as well. Plus, what are your sample values? I find it diffucult to get such a smooth look to my walls. On the same note, are you using standard materials, or Raytraced or Mental Ray?

 

Thanks for any replies, your image quality is a goal I would really like to get to.

 

François Yenny

[Fran]

Hi Francois,

 

Thanks for the encouragement.

 

I used GI but not Final gathering. I used a Daylight System with standard sun along with some mr omnis for fill and an mr spotlight at each window.

 

I have 500 Global Illumination photons and 20k GI photons in Global Light Properties. I used Global Multipliers on the sun (mental ray Indirect Illumination rollout). You'll have to play with that yourself. It is not as important for the fill lights to emit tons of photons, but I cranked them way up for the sun.

 

Probably the most important thing I have in the scene is a sphere that is large enough to encompass the scene and orbital scale of the sun. Invert the normal and set the object properties to not render and to Receive GI. This will catch errant photons and speed up processing.

[ingo]

Hi Fran,

 

the images look compared to your other images a bit flat, i have no clue why. And a bit irritating are the shadows of the chairs and the desk on the wall, they can't come from the sunlight since it doesn't get so deep into the room. If they are from the "ambient" light they have to be much smoother or nearly invisible.

 

The windows are fine, since the light outside is much much brighter the diffuse white is okay, although clients like to see the surrounding.

[Fran]

Originally posted by ingo:

the images look compared to your other images a bit flat, i have no clue why. And a bit irritating are the shadows of the chairs and the desk on the wall, they can't come from the sunlight since it doesn't get so deep into the room. If they are from the "ambient" light they have to be much smoother or nearly invisible.

I agree about the flatness (wasn't sure if it was just me). Do you mean flat in terms of contrast or flat in terms of detail? I'm not finding mr to be a very "warm and fuzzy" renderer. Doing anything with it requires a completely different strategy from what I developed with radiosity.

 

I disagree to a point about the shadows deeper in the room. They are too pronounced, but the sun would certainly penetrate the room far enough to create secondary shadowing. They need to be finessed.

 

Thanks for your insight.

[Crazy Homeless Guy]

hi fran. the images look nice. i just have what i think is a quick question more about technique, than critique. if you don't mind sharing, how do you get the glowing 'bloom' effect around the windows? i think it is a successful solution so that you don't have to show exterior.

[Ricardo Eloy]

Nice work, Fran! It's good to see people putting their hands on Mental Ray. That said, I have one question concerning the differences between Mental Ray and Max's default render. Did you find it as fast as people have been saying? I mean, everybody's talking about it, about how fast it is compared to Max's good old scanline, so I thought you might as well give us some feedback on that matter. What do you think?

Congrats!

[]

Rick

 

[ December 01, 2003, 12:05 PM: Message edited by: Rick Eloy ]

[Fran]

Originally posted by crazy homeless guy:

...if you don't mind sharing, how do you get the glowing 'bloom' effect around the windows? i think it is a successful solution so that you don't have to show exterior.

Hi Travis,

 

I did the bloom in Photoshop with the diffuse glow filter (Filters->Distort menu). I set Grain to zero and Glow to 6 or so and Clear amount to 18 or more.

[Crazy Homeless Guy]

Originally posted by Fran:

quote:

---

Originally posted by crazy homeless guy:

...if you don't mind sharing, how do you get the glowing 'bloom' effect around the windows? i think it is a successful solution so that you don't have to show exterior.

Hi Travis,

 

I did the bloom in Photoshop with the diffuse glow filter (Filters->Distort menu). I set Grain to zero and Glow to 6 or so and Clear amount to 18 or more. thanks. for some reason i thought it was rendered that way while in max. so in the rendering, the window are white, or near white?

[jucaro]

Hi Fran, The 'sphere boundary cum errant photon trapper' is a great tip. The min-max param of MR's GI engine leaves a lot to be deciphered.

 

about the image, I think the shadow on image1 is too scattered, considering your light source is a sunlight from a window. Unless you're trying to simulate a shady outdoor environment.

 

The 2nd and 3rd image shadows seem wide (evident of a shadow cast from a angled spotlight, compared to parallel shadows from a direct spot.)

 

All in all, the images look nice. What are the statistics and render times of your scene?

 

Rick:

...everybody's talking about it, about how fast it is compared to Max's good old scanline

I think this may have been a misconception that stemmed as a result from Autodesk's marketing people peddling everyone to buy or upgrade to MAX6.

 

The MR rendering engine is only as fast as the MAX default scanline renderer when you are working with standard renders (i.e. no GI or FG stuff) This is just my observation though when I compared a basic render between MAX scanline and MR.

 

I have only tried comparing MR & Vray in terms of rendering speed and acceptable quality using various scene situations from simple to complex scenes.

 

But this is another topic altogether. Sorry for hogging on your post Fran. :ebiggrin:

[Fran]

Originally posted by crazy homeless guy:

...for some reason i thought it was rendered that way while in max. so in the rendering, the window are white, or near white? [/QB]

Yes. With the diffuse glow settings I described, I don't create a selection or anything. It has very little effect on the rest of the room.

 

Rick (and Juan Carlos):

I'm finding that bitmap textures slow things waaaayyyy down. For example, this test scene with low AA renders at over 7 minutes with bitmap textures and about 2 minutes with a simple override material. This is not good. I've asked discreet about it before, but got no answer. I suspect it is a syntax issue with the scene file, but I don't know enough about it to ask the right questions, I guess.

 

I'm sure there are many ways to optimize this scene to get faster render times, but I'm finding that it averages 1.5 hours per 800x600 pixel image. The GI calcs take just a couple of minutes to complete. There are a lot of large radius area shadows in the scene, which need higher sampling, and that increases render time substantially.

 

Juan Carlos:

As for shadows, you can't do soft shadows with a directional light unless you use a shadow map. The map has to be huge in order to eliminate light leaks. All this fill light and shadow manipulation is very new to me, so it will take time and good advise to get it right.

 

[ December 01, 2003, 12:59 PM: Message edited by: Fran ]

[xgarcia]

So here is the big questions Fran:

 

Does MR workflow run faster (ie. make more money) than your usual Max radiosity workkflow?

 

Personally I prefer your previous radiosity images. These MR test images look too scanlinish, if that's a word. But I'm confident you will nail MentalRay to look like your previous work. As always excellent models, textures, and camera compositions.

[nisus]

Hi Fran,

 

Great images, but imho not as great as your finished work. (That's why you mention you are still learning MR of course...)

 

Anyway, I didn't know what 'felt different' until I took a closer/analytic look at your images. My comments are very detailed and may not be the purpose of your excercise. If they do, I hope they help you out in some way...

 

My basic critic is 'a lack of coherence' (very IMHO and unlike your other work I've seen)

 

I'll explain by means of two examples:

 

TABLES:

In image 1 and 3 the sides of the table - although parallel and not direct illuminated by the sun - appear in very different contrast. From what I see/analyse in your scene I suggest you add another omni in the center of the room, include only the smaller table and place it lower than the main omni...

(Of course, this could be done on perpose to emphasize depth... if that's the case, just ignore my comments)

 

CHAIRS:

A similair 'strange' effect is visible in the second image. The left chair is directly lit by sunlight and shows a dark shadow and a bright highlight. The chair on the righthand side has a totally different look. IMHO it should feel more like the shaded parts of the chair on the left... [although there is a strange contrast in the shadow of that chair too (back is light, side is dark)... I'm not sure what causes this effect, but my guess is an extra light perpendicular to the back, parallel to the side)

 

An overal tip might be to add small shadows around the windows to visually link them with the wall (much like the frames on the wall in your first image).

 

Ow, your ceramics material is simply superb!

 

rgds

 

nisus

[Fran]

Originally posted by nisus:

Hi Fran,

 

Great images, but imho not as great as your finished work. (That's why you mention you are still learning MR of course...)

That's why it's in the "Work in Progress" forum.

 

Originally posted by nisus:

My basic critic is 'a lack of coherence' (very IMHO and unlike your other work I've seen)

 

I'll explain by means of two examples:...

The attached image shows where the sunlight is falling. I'm not sure if that explains anything, but I am aware of the inconsistencies you've mentioned.

 

[Richard McCarthy]

Hi Fran!

 

I always like your rendering, the way you setup the scene and lighting always give this sensitive feminist feel to it (If that's the right way to say it) it's always quite different to other's rendering (99% of male CG artist here?) I think it's the use of colour as well, and the subtle lighting.

 

Great rendering (for work in progress) I don't find those problem that others mention as intrusive.

 

-RM

[ingo]

Originally posted by Fran:

I agree about the flatness (wasn't sure if it was just me). Do you mean flat in terms of contrast or flat in terms of detail? I'm not finding mr to be a very "warm and fuzzy" renderer. ....

Hi Fran,

 

i think its flat in terms of contrast. The shadows generated by the "ambient" lights or secondary rays are to defined. They had to be smoother and that way the walls get more shades of gray and don't look so flat anymore.

[Fran]

Originally posted by ingo:

i think its flat in terms of contrast. The shadows generated by the "ambient" lights or secondary rays are to defined. They had to be smoother and that way the walls get more shades of gray and don't look so flat anymore.

Hi Ingo,

 

Thanks for the clarification.

 

Hi Richard,

 

Thanks for the encouragement!

 

[ December 02, 2003, 08:45 AM: Message edited by: Fran ]

[Fran]

Hi Everyone,

 

Thanks for all the feedback. Here is an update - there are still some issues to contend with, and some to reconcile myself to.

 

[edit] I forgot to mention that I decreased the samples on the area lights from 12 to 7 and render time for this view went from 1hr 27min to 44min 19sec.

 

 

[ December 02, 2003, 11:33 AM: Message edited by: Fran ]

[ingo]

Hi Fran,

 

i still don't understand the shadows on the wall, they come from a direct light, but since the sunlight ends in the lower right corner it can't be the sun. So if the shadows come from the lights you placed in the windows they should be nearly invisible, me thinks you should make them softer.

[Fran]

Originally posted by ingo:

Hi Fran,

 

i still don't understand the shadows on the wall, they come from a direct light, but since the sunlight ends in the lower right corner it can't be the sun. ...

Hi Ingo,

 

Absolutely it can. I'm looking at it right now on my office walls. No flash BTW. Down the stairwell, lit by the same window, the shadow is more pronounced.

 

 

[ December 02, 2003, 10:11 AM: Message edited by: Fran ]

[ingo]

Hmmm....sadly we had no sun today, just a nice ambient fog light, so i can't look at it. Still a bit irritating for me to get a shadow from a nearly horizontal shining light while the sun shines from a higher angle. But if you insist on it

[joseph alexander]

Fran,

I think you need a more severe falloff, the room seems completely evenly lit. That's what's so nice about your other renders, you obviously have control over contrast, in fact mastery, these don't achieve that yet. I think as soon as you figure out how to get the back of the room dark and the front light, the renders will start to take shape.

 

(thanks again for the power translators help)

 

-joe

[pipjor]

it looks pretty dark(pure black) under the couch and 2nd chair? maybe my monitor....

[ingo]

Hi Fran,

 

thanks for the clarification with the pictures. I guess you meant the shadow from the wood (part of a children safety door ?) on the wall.

Still no sun here, i guess nisus soaks up the sun in Belgium so we didn't get the sun here

Do you use the area light only for the sun or also for the lights in the windows ? Compared to your photos i would also brighten up the sun spot on the floor on your renderings, i guess that will start to give your scene the wanted warm and fuzzy look, addditionally some warm yellow light reflection from the floor (without shadows ).

[nisus]

Still no sun here, i guess nisus soaks up the sun in Belgium so we didn't get the sun here

Sun??? What is that again? I don't remember...

 

nisus