3D World

Shot light­ing in Ren­der­man

Dis­cover top light­ing tech­niques with this ex­pert ad­vice from Ren­der­man spe­cial­ist Leif Ped­er­sen

- Leif Ped­er­sen Tech · Movies · Pixar Animation Studios · The Walt Disney Company · Adobe Photoshop · Nvidia · Mac OS X · Short Film

Leif Ped­er­sen show­cases Ren­der­man’s top light­ing ca­pa­bil­i­ties for ef­fec­tive sto­ry­telling in an­i­ma­tion

Leif is a Ren­der­man spe­cial­ist at Pixar’s Ren­der­man team, where he loves to show­case some of the most artis­tic and tech­ni­cal as­pects of the ren­derer. leif3d.com

In this train­ing we’ll use a scene from Pixar co-op short film, Only a Dream, where we’ll learn to use some of the most ef­fec­tive Ren­der­man shot light­ing tools. Dur­ing this process, we’ll un­der­stand how to make mean­ing­ful artis­tic choices in or­der to tell the best story pos­si­ble, while dig­ging into some of the more tech­ni­cal as­pects of mas­ter­ing shot light­ing in Ren­der­man for Maya.

Our main goal as light­ing artists is to tell a story, in this case, a com­ing-of-age thriller. The aes­thetic we’re go­ing for is film noir with an anal­o­gous blue/ green colour pal­ette. In fact, one of the colour in­spi­ra­tions was the Ch­ern­abog De­mon se­quence from Dis­ney’s Fan­ta­sia. In or­der to achieve our look, we’ll mix a cou­ple of dif­fer­ent light­ing tech­niques, in­clud­ing low-key and mo­ti­vated light­ing, which will give the scene a bit of drama while heav­ily art di­rect­ing the shot to cre­ate the look we need.

01 MAS­TER LIGHT­ING

A use­ful way to start is through an en­vi­ron­ment light. We’ll use a Pxr­dome­light with an in­dus­trial HDRI map which is full of small and bright light­ing fea­tures, yet of­fers dim dif­fuse light­ing. This will give us in­ter­est­ing glints to bring out shiny sur­faces. If light is over­pow­er­ing, Ren­der­man of­fers de­cou­pling of dif­fuse and spec­u­lar un­der the Re­fine tab in all lights. Us­ing light tem­per­a­ture is also a great way to stay within a plau­si­ble aes­thetic, as it’s based on phys­i­cal Kelvin colour tem­per­a­tures, but don’t be afraid to add or re­move colour for a more stylised look.

02 DI­RECT YOUR SCENE

Light­ing di­rec­tion is cru­cial for the mood of the shot, and by us­ing low-key light­ing we can start to pro­duce a scarier mood. To achieve this, we are point­ing lights from the floor to the ceil­ing to bring a gra­di­ent of light in­ten­sity in our room. Rect and Disk lights work well for this but their di­rec­tion might be too ob­vi­ous, so adding Sphere lights is use­ful when we want to cover a larger area or soften shad­ows. If you’re look­ing for fur­ther re­al­ism, try us­ing IES pro­files which will cre­ate pho­to­met­ric light pat­terns com­mon in light bulbs.

03 SHOT LIGHT­ING BLOCK­ING

The Ch­ern­abog De­mon se­quence uses com­ple­men­tary colours to its blue pal­ette to high­light key mo­ments in the sto­ry­telling, such as or­anges and yel­lows. We’re do­ing the same with our key light in or­der to bring out the warm tones in our char­ac­ter’s face. The key light is com­ing from the bot­tom left, in or­der to cre­ate that low-key aes­thetic we’re aim­ing for. We’ve also added a bounce light in an op­pos­ing di­rec­tion to shape our char­ac­ter’s face. It’s some­times use­ful to nor­malise our lights to avoid in­ten­sity changes while scal­ing the lights dur­ing our block­ing stage.

04 REFINEMENT

Light­ing is a sto­ry­telling tool, so it’s al­ways good to bring out the char­ac­ter in a shot so that it doesn’t get lost in the frame, as

this helps the viewer to fo­cus on what’s im­por­tant. To do this, we’re cre­at­ing kicker lights to high­light the hair spec­u­lar­ity and rim lights to make our char­ac­ter pop from the back­ground. Our kicker light for the hair spec­u­lar­ity is giv­ing us un­in­tended high­lights in both the eyes and face; to con­trol this, we are re­mov­ing the con­tri­bu­tion of this light via Maya’s Re­la­tion­ship Ed­i­tor>light Link­ing.

05 LIGHT FOR AN­I­MA­TION

It’s very im­por­tant not to rely on a sin­gle frame for light­ing and al­ways check the an­i­ma­tion se­quence for con­text. In our shot, the char­ac­ter starts out in penum­bra, guid­ing the viewer to the item in her hand. As the shot then pro­gresses, we shift fo­cus to the char­ac­ter’s face and her re­ac­tion to that el­e­ment in the story. To do this, we are an­i­mat­ing the light in­ten­sity of our low-key bounce light to di­rect the viewer, as well as de­creas­ing the spec­u­lar­ity of that light by 80 per cent so that it doesn’t over­whelm the eyes with reflection­s.

06 BLOCK AND ISO­LATE LIGHTS

The cur­rent setup is go­ing in the right di­rec­tion, but it’s look­ing flat, so we need to shape it fur­ther. The most com­mon way to ma­nip­u­late lights is through light fil­ters, which pro­vide a non-de­struc­tive way to block, iso­late or colour lights, even por­tals! We’re us­ing Pxr­rod and Pxr­blocker light fil­ters in this scene in or­der to shape a film-noir aes­thetic in our char­ac­ter’s face. We can sim­ply right-click on our light fil­ter at­tribute and pick from a list of avail­able op­tions. Us­ing the same tools, we’ll re­fine and shape our en­vi­ron­ment as well.

07 LIGHT GROUPS

Be­sides AOVS and LPES, Ren­der­man can out­put ar­bi­trary light groups by sim­ply as­sign­ing a light group name to the light un­der Ad­vanced>light Group. We can then go to our Ren­der Set­tings>aovs tab and cre­ate a new chan­nel to dis­play our light group, such as a new beauty pass.

Don’t for­get to check Adapt All un­der Ren­der Set­tings>

Ad­vanced, so that your new passes are not noisy.

This comes in handy for com­posit­ing, or trou­bleshoot­ing, so that you can iso­late a sin­gle or group of lights with any ar­bi­trary lobe, and you can now do this in­ter­ac­tively too!

08 LIGHT POR­TALS

Due to the sam­pling prin­ci­ples in path trac­ing, in­te­rior light­ing is usu­ally less ef­fi­cient than ex­te­rior light­ing, be­cause cam­era rays have a harder time find­ing light sources when they are hid­den from the cam­era – as in the ex­am­ple of our dome light, which is be­ing cov­ered by the house. To make this more ef­fi­cient, Ren­der­man can use por­tal lights, which com­mu­ni­cate to the ren­derer where the light­ing is com­ing from. We’re us­ing one por­tal light for each win­dow or door open­ing, which can have a dra­matic ef­fect on sam­pling qual­ity, con­verg­ing ren­ders faster.

09 REN­DER EF­FI­CIENTLY

We’re tak­ing ad­van­tage of Pxruni­fied, Pixar’s own stu­dio in­te­gra­tor, which has so­phis­ti­cated ray ter­mi­na­tion and light learn­ing tech­nol­ogy. This will al­low us to have higher trace depths for our fi­nal frames, im­prov­ing the look of our hair and skin. We also have the De­noise but­ton checked on in our AOVS Dis­play tab, which will en­able us to use the Nvidia Op­tix denoiser in the IT viewer by press­ing ‘N’ (not avail­able on OS X) and will also take care of the de­noise process au­to­mat­i­cally for batch ren­der­ing.

If your com­puter is strug­gling with re­sources, try switch­ing res­o­lu­tions or ad­just­ing sam­pling set­tings in­ter­ac­tively. •

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