Pre­pare a heavy CAD model

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at the end of 2017, New Com­mu­ni­ca­tion, a creative and mar­ket­ing agency from Kiel in Ger­many, was asked to cre­ate de­tailed im­ages of the largest Cater­pil­lar gen­er­a­tor set – the 16CM43 – for a press re­lease.

The Cater­pil­lar 16CM43 is a heavy-fuel off-shore gen­er­a­tor set that is used for power gen­er­a­tion. The brief set by the client was to use the data pro­vided by them to pro­duce this im­age, so that in the fu­ture, cut-out im­ages or de­tail shots of the gen­er­a­tor would be pos­si­ble.

From the start it was al­ready clear that this would not be an easy task, be­cause the data pro­vided by Cater­pil­lar would be of the high­est qual­ity. So be­fore we could even be­gin, we had to think about a smart and ef­fi­cient soft­ware/hard­ware pro­duc­tion pipe­line to fit ev­ery­thing into Oc­taneren­der, our ren­der­ing so­lu­tion of choice.

Our soft­ware pipe­line started with Rhinoceros 3D, which is mostly used by in­dus­trial de­sign­ers but is also great for con­vert­ing heavy CAD files. It ex­ports a very nice mesh qual­ity and works in a 64-bit en­vi­ron­ment.

We used a brand-new Dell work­sta­tion with 128MB of RAM, pro­vided by the client. It had a sin­gle 1080ti and a small graph­ics card for video out­put.

In this tu­to­rial I will show you how I han­dled the im­mense amount of data pro­vided and crunched it down for ren­der­ing.

01 Gen­eral prepa­ra­tion

Be­fore we be­gan we talked to the client and made it clear that a STEP file would be the best file for­mat for us. This way we had full con­trol over ex­port­ing into the de­sired file for­mat: FBX. When you can, it’s bet­ter to do the ex­port your­self rather than the client.

02 ref­er­ence im­ages

The client pro­vided us with many ref­er­ence im­ages from real-world gen­er­a­tor sets. These pho­tos were taken by Cater­pil­lar en­gi­neers. This was great be­cause self-taken pho­tos are mostly bet­ter than any­thing you will find on a Google search. They are high-res and give you a good ref­er­ence on even the small­est parts.

03 rhinoceros 3D/ DATA con­ver­sion

It took some time to open up the STEP file, but Rhino did so with­out prob­lems. Even if it’s prefer­able to nav­i­gate and fly around in the view­port, I sug­gest not to do it, as it can cause freez­ing. So just open the file, leave it as it is and se­lect all (Cmd+a), go to the File menu and ex­port se­lected. You can check the Layer tab and if there are lay­ers, you may ex­port sin­gle lay­ers. In my case there weren't, so I had to ex­port ev­ery­thing in one file.

04 DATA prep in cinema 4D: con­sid­er­a­tions

Rhino ex­ported in ten hours which was re­trace­able by the time the file was writ­ten on the sys­tem. So we had our nicely ex­ported FBX file, which had grown to a size of 3.75 gi­ga­bytes. Luck­ily it was un­der 4 gigs, be­cause that is the max size for FBX at the mo­ment.

Af­ter a few min­utes, check­ing RAM con­sump­tion as well, Cinema 4D opened the file. So I first saved a *.C4D file out of it be­fore do­ing any­thing else. Af­ter sav­ing the C4D I recog­nised that the Cinema 4D file was grow­ing to an im­mense 8 gigs. The first thing you can do is delete all UV tags to get the file al­most 50 per cent smaller.

05 or­gan­i­sa­tion

So how could I prep the file if I was not able to see any­thing? I de­cided to go for a sim­ple but ef­fec­tive way of cut­ting out a spe­cific amount of ob­jects and pasting them into a new blank scene. This worked very well as Rhino ex­ported ev­ery­thing or­derly so that ob­jects in a row were parts of a sin­gle gen­eral part.

The main chal­lenge was to fig­ure out how many ob­jects to cut out. I tried dif­fer­ent ob­ject counts, and fur­ther in the project I was lucky to hit al­most the cor­rect num­ber of ob­jects that be­longed to­gether. Ob­jects that did not be­long to one part were sep­a­rated as null ob­jects.

06 cinema 4D helpers

So af­ter fig­ur­ing out how to merge down this many ob­jects I had to think a bit fur­ther. Keep­ing

check your specs Be sure to have enough RAM in your ma­chine when you work with heavy CAD files.

in mind that we wanted to use Oc­tane Ren­der, know­ing the VRAM of the graph­ics card is the crux of the mat­ter. So I had to use a good bunch of Cinema 4D's Cloning Sys­tem and other small helpers that crunch the file down to a size that fits into the VRAM. There are many op­tions to help you with this, like ar­rays, in­stances, xrefs and of course Mo­graph Clones.

07 work with Xrefs

For the heav­i­est parts (re­fer­ring to the poly­gon count of the ob­ject) I de­cided to use the xref sys­tem of Cinema 4D. Sin­gle ob­jects were saved as new C4D files and then could be loaded as an xref into the main scene. Your scene per­forms quite a bit faster when you have heavy ge­om­e­try ex­cluded into an xref file. You can work on it in the ex­cluded file and hit re­fresh on the xref to up­date your ob­ject.

08 use The r19 poly­gon re­duc­tion Fea­ture

A freshly new fea­ture in R19 was the poly­gon re­ducer, which came in very handy! This works even with com­plex CAD ge­om­e­try. Sim­ply use it like a mod­i­fier ob­ject and af­ter some cal­cu­la­tion time you can see the re­sult. So for some ob­jects that had quite a large amount of poly­gons I made a lower ver­sion of some parts, just like a level of

Try it out first You can use a fully func­tional ver­sion of Rhinoceros 3D as a 90day trial, if you’d like to test out its fea­tures.

real-world scale Al­ways work with cor­rect real-world sizes in your scene. It’s help­ful when set­ting up cam­era and lights as well.

de­tail. The re­duced parts were used if the cam­era was some dis­tance away from the ob­ject.

09 Ar­rays

When you have ob­jects that are aligned in a ring-like pat­tern, ar­rays will come in handy. You can even check Ren­der In­stances to get more per­for­mance. I like ar­rays a lot, as I find that they per­form very well. Just put the de­sired ob­ject in the ar­ray and with the help of the pa­ram­e­ters you can ad­just al­most ev­ery­thing you need.

10 Mo­graph clon­ers AND in­stances

One of the most pow­er­ful in­stanc­ing sys­tems within Cinema 4D is Mo­graph and Mo­graph clones. This is the fea­ture I used most of the time. Ev­ery time a sin­gle ob­ject re­peats it­self a spe­cific amount of times, use Mo­graph. So for ex­am­ple I used it for cloning the cylin­der heads, ev­ery­thing that’s un­der­neath, or screws that were aligned on the out­side. You can even gen­er­ate an in­stance out of a cloned ob­ject, or use it in a sym­me­try ob­ject. Some­times it’s even use­ful to merge down a large num­ber of ob­jects.

11 ren­der in­stances AND oc­taneren­der

When you are us­ing mul­ti­ple clones in­side of Cloner, be care­ful. Some­how Oc­tane re­fuses to ren­der these cloned clones when they are checked as Ren­der In­stances. Be sure to look af­ter that be­fore ren­der­ing. Other en­gines like V-ray, Corona or the de­fault C4D Ren­der will ren­der it any­way.

12 or­gan­ise your scene

Be sure to have a good, ef­fi­cient method for or­gan­is­ing your scene. You will avoid trou­ble when you have a nice and clean struc­ture. For ex­am­ple, you can use lay­ers or null ob­jects to get ev­ery­thing or­gan­ised. When you have in­for­ma­tion from the client, it’s nice to name ev­ery­thing cor­rectly too. You can use ‘Icon Color’ for null ob­jects to split ev­ery­thing fur­ther in the ob­ject man­ager.

13 Delete Faces Man­u­ally

On very com­plex ge­om­e­try where the poly­gon re­ducer re­fused to work, I man­u­ally deleted poly­gons that would not be vis­i­ble – ba­si­cally ev­ery­thing that’s in­side and hence not im­por­tant for a hero shot. When you delete faces, Cinema 4D will leave the ver­tex points, so be sure to op­ti­mise your scene and check ‘Delete Un­used Points’ and you are ready to go. Be sure that you leave the orig­i­nal ge­om­e­try as a sin­gle saved file for a backup.

14 set up scene/ cam­era po­si­tion

For these im­ages I used a pretty long fo­cal dis­tance to avoid dis­tor­tions from the cam­era lens. A nice ad­di­tional way to get rid of these is hid­den in the Oc­tane cam­era tag: Per­spec­tive Cor­rec­tion.

15 Model weld­ing seams

For some parts it was nec­es­sary to model weld­ing seams. There are two ways to do this: mod­el­ling, or with a weld dis­place map. I de­cided to go for mod­el­ling be­cause it’s faster.

In my case I needed a ring-like weld seam. So, sim­ply use a ring ob­ject. Con­vert it to an ed­itable Poly­gon, go to Point mode and se­lect all Points. Use the ‘Set point value’ com­mand in the At­tribute win­dow, choose ‘Crum­ple(ax­ial)’ from the menu and try some val­ues un­til you get your de­sired look.

16 Ad­di­tional helpers

If you barely have time to fin­ish your work and there is an in­creas­ing work­load, you can cheat a lit­tle on mod­el­ling when you sim­ply use tex­tures with bumps and nor­mals. There are a lot of free tools on the mar­ket that are good for these pur­poses.

For ex­am­ple, Crazy­bump. I used this for an ana­log In­ter­face with some but­tons and some scale in­di­ca­tors as seen in the screen­shot.

17 clay ren­der­ing

When your model is set up in the way you want it, it’s al­ways nice to do some ren­der­ings in clay ‘mode’. It’s also a way to test if Oc­tane ren­ders it out or if there are any me­mory is­sues. So this is a smart method to test your scene and to have some first im­ages for your client that look bet­ter than some Opengl screen­shots.

You can use the day­light sys­tem with a sun or an HDRI en­vi­ron­ment, or sim­ply use the de­fault back­ground colour from Oc­tane and hit ren­der.

18 shade in oc­tane For A heat-ex­posed look

For tex­tur­ing/shad­ing I used the ref­er­ence im­ages that were pro­vided to build up some shaders. Mostly it was straight­for­ward. Use cor­rect IOR val­ues when you do glossy ma­te­ri­als. To break it up a bit I made a shader that looks like some parts were threaded with heat. It’s easy to do with Oc­tane Dirt in in­verse mode and a ramp with some nice colours to make it look like it was ex­posed to great heat.

19 light­ing in oc­tane

I de­cided to light it man­u­ally rather than us­ing an HDRI or us­ing HDRI Stu­dio, which is a great tool by the way. I placed Area lights around the en­gine and used smaller Area lights to lighten up spe­cific points of in­ter­est. You can uncheck ‘Vis­i­ble for Spec­u­lar’ in the light op­tions when you just want it for the dif­fuse or the other way. I also mixed some light colours to make it a bit more in­ter­est­ing. You can use the Kelvin slider in the light op­tions for the Oc­tane Light to do this.

20 ren­der set­tings in oc­tane

Ba­si­cally Oc­tane's ren­der set­tings are not that com­pli­cated; there’s not that much you can do wrong. I use the path tracer al­most ev­ery time as my main ren­der ker­nel. Be sure to have enough sam­ples es­pe­cially when you are work­ing with depth of field. There­fore, here we need some more sam­ples and it may even take a while un­til it’s free of noise.

When you have fire­flies or hotspots in your ren­der­ing, use the GI Clamp slider and lower it down un­til they dis­ap­pear. In the Oc­tane tab in the main ren­der set­tings en­able Ren­der Passes and choose your lay­ers for later post­pro­duc­tion. Use 16 or 32-bit im­ages when you are sav­ing your im­age.

21 post-pro­duc­tion

With the ren­dered multi-pass im­age I did some mi­nor colour cor­rec­tions in Pho­to­shop. As al­ways

I used a slight amount of Am­bi­ent Oc­clu­sion with a mul­ti­ply around 10-20%. Don’t use more, it will look un­nat­u­ral and dirty. With the ma­te­rial ID and the Pho­to­shop colour se­lec­tion I was able to do a quick se­lec­tion of parts that needed a bit more tweak­ing. Use the se­lec­tion to cre­ate masks and colour cor­rect in a non-de­struc­tive way. With the lay­ers in­cluded in your multi-layer im­age you can sim­ply ad­just the opac­ity, for ex­am­ple, for more re­flec­tion. For the ground shadow I used Cinema 4D's de­fault ren­der Am­bi­ent Oc­clu­sion be­cause I like it more than the Oc­tane Oc­clu­sion pass.

22 proof Fi­nal re­sults

One of the main tasks was to get as close as pos­si­ble to the typ­i­cal Cater­pil­lar yel­low, even in print! So we used our Print Proofer here at New Com­mu­ni­ca­tion to get as close as we could. We needed sev­eral at­tempts to get the de­sired re­sult. If you have re­flec­tive ma­te­ri­als on your ren­der it’s not easy to grade the colours to the ref­er­ence. So my ad­vice is to look for a re­gion on your ren­der where there’s al­most no re­flec­tion go­ing on, no shad­ows and no self shad­ow­ing. It’s the best place to do the grad­ing. We used Pho­to­shop to do the job but you can do it in other post-pro­duc­tion soft­ware as well.

Au­thor Michael Tsch­ern­ja­jew Michael works for New Com­mu­ni­ca­tion, a lead­ing creative agency in Ger­many. new-com­mu­ni­ca­tion. de

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