Newbie with GI and Cinema4D

[vgalov]

Hello,

 

We started using Cinema4D recently and I was really inspired by the images posted here by Paul Griger. Thanks Paul All modeling was done in ArchiCAD and exported through .Obj file format.

 

Switching from software only with raytracing to one with realistic Radiosity was really a challenge for us. And still is.... Probably will always be

 

Unfortunately I can't upload here VR panorama movies. But the images that are included will represent better the problems that we have with the GI solutions. These are cropped directly from the intermediate source for creating VR movs.

 

http://www.cgarchitect.com/forum/filepush.asp?file=Family.jpg

 

This image is my first rendering with radiosity. The settings are:

 

Strenght 150

Acc 70

PP 1/1

Diffuse Depth 3

Stochastics 300

Min res 50

Max res 200

 

Everything was OK until I placed the rest of the furniture in this model - total number of polygons around 1200000, and this is only the first floor. I carefully switched off all the elements that were not seen by the VR camera and I didn't wait for the rendering to finish-20 hrs.

 

So I started changing the Radiosity settings. We came down to 10 hrs with the solution. But it is not good enough...

Strenght 300

Acc 70

PP 1/1

Diffuse Depth 1

Stochastics 600

Min res 50

Max res 300

 

The family room looked decent, not the best ( still a lot to learn ), but some splochiness in the kitchen really frustrated me.

 

http://www.cgarchitect.com/forum/filepush.asp?file=FamilyVR.jpg

 

Here is the kitchen from the same solution with the family room:

http://www.cgarchitect.com/forum/filepush.asp?file=KitchenVR.jpg

 

I changed the camera location and with the same solution rendered the Kitchen VR: I was shocked by the result?

 

http://www.cgarchitect.com/forum/filepush.asp?file=KitchenVR_1.jpg

 

I thought that the samples for the max res are not enough as well as the samples and increased their number:

Strenght 300

Acc 70

PP 1/1

Diffuse Depth 1

Stochastics 750

Min res 50

Max res 350

This added hour and half to the render , but not to the quality of the image.

 

http://www.cgarchitect.com/forum/filepush.asp?file=KitchenVR_2.jpg

 

http://www.cgarchitect.com/forum/filepush.asp?file=KitchenVR_3.jpg

 

My Dell Workstation is with Dual Xeon 2.0 CPUs, 2 GB RAM .

 

Please don't hesitate to criticize. This is the only way that anyone can really improve.

Waiting for your comments

Thanks in advance

[STRAT]

a few tips -

 

take off the blur material, this'll speed up rendering like there's no tomorrow!!! if you need to blur then render to photoshop layered file and blur in there.

 

prepass size - an acceptable pp size would be 2 or even 3. this again will speed up ur rendering.

 

The strange blochyness is not just due to the accuracy settings, but also the high strength value - anything over 100 is usually un-natural and over exposed. to lighten the scene either add extra fill lights or up the diffuse depth a few notches (3 is pretty good for internal shots).

Also to improve the quallity of the images try upping the accuracy as much as poss. then the higher the accuracy goes you can start to lower the samples.

 

try something like:

 

Strength - 100

Acc - 85

pp - 3

dd - 2 (or 3)

stoches - 300

min - 50

max - 150 (i usually use a value which is about 50% of the stoches value)

 

the biggest speed increases will be NOT using blur slot in the reflective material, and the diffuse depth. if rendering time is still too high then keep a diff depth at 1 and add a couple off fill omnis just to up the lighting levels.

 

The strength of GI can also be individually controlled by render tags and material properties.

 

render options - you can speed up rendering here too:

 

Ray depth - number of times alpha or clear materials are rendered. 4-6 is fine, no speed issues here usually

 

Ref depth - number of times reflections are bounced. i personally use 1 on allot of jobs. this does increase render speeds.

 

Shad depth - number of times shadows render. again, depending on transparancies and scene settup try 2 or 3. this also increases speed.

 

Threashold - reflection detailing. kinda like a fine tuning to the reflection value slider. i normally use a value like 10-15% (again, depending on scene). more speed increases.

 

L of D - this value determins the detail of primatives/nurbs etc (ie, non editable objects)

if no primatives are used then this value wont effect speed.

 

Again, the above is a guide and based on the scene ur currently working in.

 

As far as QTVR resolution is concerned i normally just render out as big an image i can afford the time to render.

 

also go look here for extra little render speed tips - http://www.cgarchitect.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=12;t=000002 and look at the headings in the cinema4d forum in cgarchitect for more tips.

 

this site explains c4d's radiosity in detail - http://www.mvpny.com/RadTutMV/RadiosityTut1MV.html

 

p.s. - upgrade to release 8.1 too, the render speeds really are much faster, and with a fast pc like what like you have stochastic mode rendering is now more faster than ever!

 

[ March 17, 2003, 02:42 AM: Message edited by: STRAT ]

[Paul Griger]

Wow, I inspired someone in positive way, that’s nice to hear.

 

Strat has covered many good points in his crit.

 

If I’d add anything to say to that:

 

1. some have said that they use a ratio of 1 – 10 for min & max res. When monkeying with the res, set your accuracy at say 70% like you have it and THEN LEAVE IT ALONE! If you have to fine tune the accuracy, use the min & max after that. Understand that min & max are exponentially affected by the accuracy setting. Say you have the min at 50 and max at 500, well multiply that by your 70% accuracy and that’s your true final accuracy setting. When fine tuning things, if you change more than one variable [say the max res and the accuracy %] you’ll NEVER find the optimal setting.

 

2. the last link Strat posted is an excellent toot in radiosity. If you haven’t done anything else yet on Strat’s list, do that 1st!

 

3. if I’d have to guess, it looks like the artifacts at the casing are due to a max setting that is too low. And Strat is right, setting the GI strength above 100 seems to make things hotter and gives you a better chance for slothiness.

 

4. lose the blur. Blur KILLS your radiosity calc speed.

 

The overall lighting looks good. I was happy when I saw the pics that you did them with C4D because the lighting looks believable overall.

 

best,

 

paul

[vgalov]

Thank you very much for the extensive remarks and comments. Especially for the Blur... never knew that..Is it the same with the Displacement Illumination?

 

I hid all the furniture and accessories and started to experiment systematically on the settings.As Paul advised i locked the strength(100%) and the accuracy(70%)- adjusted the Stochs and min and max values.

 

I want to achieve realistic looking image only stressing on the exterior light, and later to add the interior lights for each room.Do you think this is the right way or I should first start with the accent lights. Adding additional omnies to the scene is kinda artificial, reminds me of Art*lantis... :

 

For exterior light i use a half sphere with Luminance at 300% and Sun light with sharp shadows at 250%. I took this settings from the examples that arrived with the C4D package.

Strat, I read your comments on the HDRIs, any other suggestion for realistic exterior illumination?

 

Here are some of the tests with times.

 

test01

DD 1, Stoch 300,min 75, max 150, pp 1, time 04:58

 

http://www.cgarchitect.com/forum/filepush.asp?file=Test01New_1.jpg

 

test03

DD 1, Stoch 600,min 75, max 300, pp 1, time 12:37

 

http://www.cgarchitect.com/forum/filepush.asp?file=Test03New.jpg

 

test09

DD 3, Stoch 150,min 25, max 75, pp 1, time 12:55

http://www.cgarchitect.com/forum/filepush.asp?file=Test09.jpg

 

test10

Increasing the Stochs to 300, min 50,max 150,did not help much but the time - 1:16:03

 

http://www.cgarchitect.com/forum/filepush.asp?file=Test10.jpg

The time is for image size 320/240

 

I checked all the setting in the prefrencesfor Multithreding ..- Optimal

 

Is the exterior illumination the problem?

 

Thank you in advanve

Best regards

Viktor

[STRAT]

ultimately, to get more realistic lighting, you need to either use stoch mode rendering or set normal gi accuracy as high as possible. in the 90's atleast.

 

but this slows down rendering.

 

we use additional fill omnis inside for this very reason. ideally you'd use a skydome and a sun spot for the external GI and lighting, and set the DD to 4 or 5 or sommit, but this takes aaaaaggggeeeessssss to render.

 

for my scenes i use 2 spheres around the scene: -

 

1 sphere around the whole scene with a blueish luminance material applied to it (set to about no more than 100% usually). this is the gi sphere, and a render tag should make it invisible to all except GI.

 

and another similar sphere i use for the backround or sky image. this should be made invisible to all except rays and camera.

 

internally you'd ideally use a nice dd of 3+, but since most of us dont own super computers a value of 2 is used with some low light emmitting attenuated omnis. this is quite normal.

 

your new tests certainly look better, but i really wouldn't be afraid of adding a few omnis in and lowering the dd to 2 or sommit.

 

but again, each scene is unique and individual. you'll have to experiment.

 

my opinions about HDRI - cinema cant actually output a 64 bit image, it'll crop the colour value down, but it can use hdr maps for rendering purposes.

Take a look at my HDRI thread at the tut i posted for tips. You'll not see a big noticable result in hdri rendering, especially not all the hoo-har everyone bangs on about, (that goes for every 3d app), but you will notice an extra 'lift' or sparkle to certain reflective or shiney elements to the scene.

Ultimately it's image based lighting you're talking about here and not hdri rendering.

 

Also you asked about displacement illumination?

you got that slightly wrong.

It's 2 separate options. displacement AND illumination.

displacement is a material slot, hence the check box, and illumination is a general properties box.

 

And no, it's not a blur tool. displacement works similar to displacement mesh mapping. look at the help files to see further.

[ingo]

Originally posted by STRAT:

for my scenes i use 2 spheres around the scene: -

 

1 sphere around the whole scene with a blueish luminance material applied to it (set to about no more than 100% usually). this is the gi sphere, and a render tag should make it invisible to all except GI.

 

and another similar sphere i use for the backround or sky image. this should be made invisible to all except rays and camera.

Why dont you use the backround sphere also for GI ? Gives more realistic results i guess.

 

ingo

[STRAT]

because c4d has a funny way of applying that.

 

doing it that way would make the objects that pick up the gi look almost invisible. it maps the backround and the GI solution in the same 3dspace, so using the backround as the gi would kinda make things look see through. thats why backround and gi need 2 diff mapping co-ords to work.