3D World

Ren­der with a sky­dome Hdri in maya

Dis­cover how to ren­der a re­al­is­tic scene with a sky­dome light us­ing the Arnold ren­der en­gine in Maya

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Find out how to ren­der a re­al­is­tic scene with a sky­dome light us­ing Arnold in Maya

The Arnold ren­der­ing en­gine by Solid An­gle is the new­est pho­to­re­al­is­tic ren­derer in­stalled by de­fault in Maya 2018. Arnold uses phys­i­cally based ren­der­ing to ac­cu­rately sim­u­late light­ing in the real world. When ren­der­ing scenes that re­quire re­al­is­tic light­ing from an en­vi­ron­ment, an Arnold sky­dome light is par­tic­u­larly use­ful. It is com­bined with an im­age file for light­ing in the en­vi­ron­ment, and can be used for re­flec­tions on ob­jects.

The im­age file used for a sky­dome must con­tain suf­fi­cient im­age in­for­ma­tion. Nor­mal dig­i­tal pho­to­graphs do not con­tain enough in­for­ma­tion cap­tured from the ac­tual en­vi­ron­ment to re­pro­duce the light­ing in­for­ma­tion. The Im­age-based Light­ing (IBL) uses a High Dy­namic Range Im­age (HDRI) mapped to the sky­dome to re­pro­duce light­ing in the scene.

The equirect­an­gu­lar 360 is a spher­i­cal or Lat­long im­age file, and is one of the more com­mon en­vi­ron­ment map pro­jec­tions; it is com­monly used in map­ping the Earth onto a flat sur­face. Sim­i­larly, when cap­tur­ing a 360 photo, it projects the en­vi­ron­ment as a sphere onto a flat plane.

There are sev­eral ways to cap­ture an equirect­an­gu­lar 360 photo of an in­te­rior or ex­te­rior en­vi­ron­ment. Dif­fer­ent cam­eras and dif­fer­ent meth­ods will pro­duce vary­ing re­sults. The meth­ods will vary based on your bud­get, or what sort of cam­era you have ac­cess to. For this tu­to­rial, I am pro­vid­ing an HDRI for you to use, and I will demon­strate how to use any HDR im­age as a sky­box and cre­ate a re­al­is­tic ren­der in Maya us­ing Arnold.

01 cap­ture An hdr im­age

You can use ei­ther a 360 cam­era or a dig­i­tal cam­era on a nodal tri­pod head to shoot pic­tures of an en­vi­ron­ment you want to use. There are some won­der­ful com­pact 360 cam­eras on the mar­ket right now, but a nodal tri­pod head will work with a stan­dard dig­i­tal cam­era. There are many re­sources on the in­ter­net for tak­ing HDR pho­tos.

02 merge im­age files of brack­eted ex­po­sures

There are sev­eral soft­ware pack­ages that can do this – since I use Pho­to­shop, there is a built-in Merge to HDR func­tion. In Pho­to­shop, choose the File menu>au­to­mate> Merge to HDR Pro. This will ask you for the im­ages to com­bine and the ex­po­sure dif­fer­ence be­tween each im­age. If you have Adobe Cre­ative Cloud, and have Adobe Bridge in­stalled, you can also se­lect the im­ages and choose Tools>pho­to­shop>merge to HDR Pro. Once com­bined the im­ages will need to be con­verted to 32bit, and then saved as a Ra­di­ance (HDR) or OPENEXR for­mat.

03 Save im­age file

Save the im­age file as an OPENEXR or Ra­di­ance (HDR) file. When us­ing Pho­to­shop, if nei­ther of the two file for­mats are avail­able when sav­ing, make sure the im­age mode is set to 32 bit (Im­age>mode>32 Bits/chan­nel).

04 Stitch im­age

If needed, use stitch­ing soft­ware to com­bine the im­ages to cre­ate the fi­nal equirect­an­gu­lar 360 im­age file. If you are us­ing

Pho­to­shop, choose the File menu>au­to­mate>pho­tomerge. Then se­lect the files or an en­tire folder con­tain­ing the im­age files to com­bine. Try the auto lay­out func­tion first, but if that doesn’t give you the best re­sults then try other lay­out meth­ods.

05 Set the maya project Direc­tory

Use the in­cluded project files through this tu­to­rial. It’s al­ready a project direc­tory and just needs to be set as the Maya project be­fore the scene file is opened. Do this by start­ing up Maya first, then choose File>open Scene. In the Open win­dow, click the Set Project but­ton. In the Set Project win­dow, se­lect the direc­tory for the project (just click once on the project direc­tory to high­light it) then click the Set but­ton. When the Set Project win­dow closes, choose the scene file hdr_sky­dome_2018_s­tart.ma and click the Open but­ton.

06 maya Scene file

You can ei­ther use the scene file I pro­vided for this tu­to­rial, or you can cre­ate your own scene. Based on the 360 photo you use, this scene can be ei­ther an in­te­rior or ex­te­rior en­vi­ron­ment. This tu­to­rial uses some ba­sic ob­jects in the out­doors and al­ready has some tex­tures for a ta­ble in the scene.

07 en­able the Arnold plu­gin

The Arnold plu­gin adds a top-level menu in Maya, ti­tled Arnold. If this menu is not avail­able it could be that the Arnold ren­der plu­gin is not en­abled. Arnold is the de­fault pho­to­re­al­is­tic hard­ware ren­der en­gine in­stalled with Maya 2018. From the Win­dow menu>set­ting/ Pref­er­ences>plug-in Man­ager, look for the mtoa plu­gin and check the box next to Loaded.

08 pre­pare the hdr im­age

Place an HDR equirect­an­gu­lar photo in the sour­ceim­ages direc­tory of the Maya project direc­tory. I in­cluded one of my HDR equirect­an­gu­lar 360 im­ages for you to use, but you can cer­tainly use one you cre­ated. There are also many re­sources on the in­ter­net where

you can down­load and use HDR IBL im­age files. Make sure that you are us­ing a true HDR file.

09 ADD A Direc­tional light

First off, if you are cre­at­ing your own scene, and cre­at­ing an in­te­rior scene, you will not need to add a direc­tional light. Direc­tional lights mimic light from the sun. This type of light projects light rays that are par­al­lel and orig­i­nate from the di­rec­tion the light is fac­ing. Ro­tat­ing this light changes the di­rec­tion of the light rays. Trans­lat­ing (mov­ing the light around the scene) will not change the di­rec­tion of this light at all. Choose Cre­ate>lights>direc­tional Light.

10 use Direc­tional lights

Since the sky­dome light af­fects the scene with colour and light emit­ted from the im­age file, this can af­fect the colour of tex­tures used in the scene. For in­te­rior scenes an HDRI file con­tains light­ing in­for­ma­tion that is more re­al­is­tic, so us­ing an in­te­rior light is not nec­es­sar­ily re­quired, and the IBL could be suf­fi­cient for the scene. Since the sun pro­vides so much light in the out­doors, adding an ad­di­tional light will pro­vide more re­al­is­tic shad­ows and light­ing in the scene, while the IBL pro­duces ad­di­tional light­ing in­for­ma­tion and adds re­flec­tions.

11 ADD An Arnold Sky­dome light

The Arnold ren­der en­gine adds some of its own lights. While Arnold can use Maya stan­dard lights to add im­age-based light­ing (IBL), Arnold uses its own sky­dome light. This cre­ates a sphere in the scene that can have an im­age file mapped to the colour chan­nel. Add the sky­dome by choos­ing Arnold>lights>sky­dome Light.

12 map im­age file node

To map an im­age file to the sky­dome light, con­nect an im­age file node to the colour chan­nel of the sky­dome light. Just like all map­pable chan­nels in Maya, click the check­ered box next to the colour chan­nel in the Sky­dome Light at­tributes in the At­tribute Edi­tor. In the Cre­ate Ren­der Node win­dow,

se­lect the 2D Tex­ture sub­sec­tion un­der the Maya sec­tion on the left side of the win­dow, then click the File op­tion in the right-hand side of the win­dow.

13 con­nect the hdr im­age file

Click the folder icon next to the Im­age Name in the Im­age At­tributes sec­tion of the At­tribute Edi­tor. In the Load Im­age File win­dow, choose the sour­ceim­ages direc­tory, and se­lect the HDR equirect­an­gu­lar photo to use. Then click the Load but­ton. You should now see the im­age on the sky­dome light’s ge­om­e­try in the scene.

14 Set Sky­dome light At­tributes

In the Out­liner win­dow, choose the aisky­dome­light to see its at­tributes in the At­tribute Edi­tor. Set the Res­o­lu­tion at­tribute to the same width of the im­age file used. The im­age I used is 7,744 pix­els wide, so this at­tribute is set to 7,744. Never set this at­tribute higher than the hor­i­zon­tal res­o­lu­tion of the HDR map, as Arnold uses this to cap­ture de­tails from the im­age file. Make sure the im­age is set to Lat­long for equirect­an­gu­lar 360 im­ages. Keep the Ex­po­sure at­tribute set at zero. Chang­ing this at­tribute will ad­just the in­ten­sity of the light­ing in the im­age. Make sure that Il­lu­mi­nates By De­fault is en­abled.

15 cre­ate A ren­der cam­era

Cre­ate a dif­fer­ent cam­era to use for ren­der­ing. To cre­ate a new cam­era in the scene head to Cre­ate>cam­eras>cam­era. Re­po­si­tion the cam­era in the scene by trans­lat­ing or ro­tat­ing.

16 name the new cam­era

Change the name of the cam­era to some­thing dis­tinc­tive, I call my ren­der­ing cam­eras Shot­cam­era. With the new cam­era se­lected open the At­tribute Edi­tor for the cam­era’s trans­form node at­tributes, and en­ter the new name. Do not change the name of the shape node. Chang­ing the name of the cam­era’s trans­form node will up­date the name of the shape node au­to­mat­i­cally.

17 view through the cam­era

Look through the cam­era by choos­ing the Pan­els menu in the main view­port, se­lect Per­spec­tive> Shot­cam­era1, or the name of the

ren­der­ing cam­era. Now you can move the cam­era around with the nor­mal cam­era move­ment tools. Turn on the Res­o­lu­tion Gate in the view­port to see what will ren­der.

18 change ren­der Set­tings

Open the Ren­der Set­tings win­dow, from Win­dows>gen­eral Edi­tors>ren­der Set­tings and make sure Arnold Ren­derer is the se­lected ren­der en­gine in the Ren­der Us­ing menu at the top. You can also change the Im­age Size to the tar­get size to ren­der.

19 test the Arnold ren­der

While Maya has a Ren­der View win­dow, the Arnold Ren­derview win­dow is a bet­ter method when ren­der­ing with Arnold. From the Arnold menu, se­lect Ren­der, this will open the Arnold Ren­derview win­dow and start a sin­gle frame ren­der au­to­mat­i­cally.

20 change Direc­tional light Set­tings

If the ren­der is too dark, you can ad­just the in­ten­sity of the light, or ad­just the Ex­po­sure at­tribute in the Arnold set­tings in the At­tribute Edi­tor for the light. To make shad­ows softer, ad­just the An­gle value. This is the an­gu­lar size of the light in de­grees. A larger An­gle value will soften shad­ows in the scene. Chang­ing the Sam­ples value in the At­tribute Edi­tor to more than 3 will im­prove the edges and de­tail of the shad­ows. Be aware that in­creas­ing this value too high will dras­ti­cally in­crease ren­der times.

21 Ad­just light Di­rec­tion

Se­lect the Di­rec­tion Light, and press the ‘e’ key to ro­tate the light. Change the di­rec­tion of the light so that the ar­rows are fac­ing in the same gen­eral di­rec­tion as the sun in the sky­dome im­age. While this does not need to be ex­act, it should be in the same gen­eral di­rec­tion so that the shad­ows are fac­ing the cor­rect di­rec­tion.

22 Depth of field

Ev­ery­thing in the fore­ground and the back­ground in the cur­rent ren­der will be in fo­cus, which might be ideal, but does not look very re­al­is­tic. If this was a picture taken in the real world, due to the na­ture of the cam­era lens, it would not be able to keep ev­ery­thing in fo­cus. Adding depth of field to the ren­der cam­era will cre­ate a more re­al­is­tic and be­liev­able ren­der.

23 De­ter­mine Dis­tance to the cam­era

Look­ing through the ren­der­ing cam­era, de­ter­mine the dis­tance to an ob­ject by se­lect­ing it in the scene and check­ing the Dis­tance From Cam­era value in the Heads Up Dis­play. This will be in the up­per

right of the main view­port; if this is not dis­played, turn it on by choos­ing Dis­play>heads Up Dis­play and check the Ob­ject De­tails op­tion.

24 en­able Depth of field

Se­lect the ren­der­ing cam­era and scroll down to the Arnold sec­tion in the At­tribute Edi­tor. Check the box next to the En­able DOF at­tribute. En­ter the value of the ob­ject dis­tance to the cam­era into the Fo­cus Dis­tance. This value does not have to be ex­act, es­pe­cially since the dis­tance to an ob­ject is where the pivot point is lo­cated.

25 change Arnold Set­tings

The Arnold Ren­derview will up­date as the depth of field is ad­justed. In­crease the Aper­ture Size to make less of the back­ground and fore­ground in fo­cus in the ren­der – this is called a shal­low depth of field. When the back­ground and fore­ground are both in fo­cus, it is called deep depth of field. De­crease the Aper­ture Size value in or­der to achieve a deeper depth of field.

26 Set up for fi­nal ren­der­ing

Open the Out­liner win­dow, and se­lect the aisky­dome­light. In the At­tribute Edi­tor in­crease the Sam­ples to 3. In­creas­ing this value im­proves the edges of the shad­ows. Al­though, in­creas­ing this value too high will dras­ti­cally in­crease the ren­der times.

27 change the ren­der op­tions

Open the Ren­der Set­tings win­dow and se­lect the Arnold tab. Change the AA Sam­ples, which is set to 3 by de­fault. Since we are in­clud­ing cam­era depth, in­crease this value to 7 or higher.

28 ren­der the fi­nal im­age

Switch to the Shot­cam­era (ren­der­ing cam­era), open the Arnold menu and se­lect Ren­der. Again, this will open the Arnold Ren­derview win­dow and start a sin­gle frame ren­der. Ad­just­ing any set­tings in Maya will restart the ren­der, but al­lows you to in­ter­ac­tively see the re­sults. •

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 ??  ?? re­al­is­tic light­ing Arnold’s sky­dome light can be used with hdr im­ages to per­form im­age­based en­vi­ron­ment light­ing
re­al­is­tic light­ing Arnold’s sky­dome light can be used with hdr im­ages to per­form im­age­based en­vi­ron­ment light­ing
 ??  ?? Stephen Studyvin is a VFX and an­i­ma­tion artist and ed­u­ca­tor, teach­ing and work­ing in Maya since 2000. He has an MFA in An­i­ma­tion from Acad­emy of Art in San Fran­cisco. art­sta­tion.com/ pixonti
Stephen Studyvin is a VFX and an­i­ma­tion artist and ed­u­ca­tor, teach­ing and work­ing in Maya since 2000. He has an MFA in An­i­ma­tion from Acad­emy of Art in San Fran­cisco. art­sta­tion.com/ pixonti
 ??  ?? what is an hdri? High dy­namic range, or HDR im­ages, cap­ture the en­tire dy­namic range of the vis­i­ble world. In stan­dard dy­namic range im­ages, a cam­era can­not cap­ture bright sun­light and dark shad­ows at the same time. Pho­tomerge func­tion in Pho­to­shop’s File menu 04
what is an hdri? High dy­namic range, or HDR im­ages, cap­ture the en­tire dy­namic range of the vis­i­ble world. In stan­dard dy­namic range im­ages, a cam­era can­not cap­ture bright sun­light and dark shad­ows at the same time. Pho­tomerge func­tion in Pho­to­shop’s File menu 04
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 ?? maya project direc­tory When start­ing new projects in Maya, es­pe­cially since this scene will pull from sev­eral im­age files, cre­at­ing or set­ting a Maya project direc­tory will help to keep ev­ery­thing or­gan­ised. ?? 09
maya project direc­tory When start­ing new projects in Maya, es­pe­cially since this scene will pull from sev­eral im­age files, cre­at­ing or set­ting a Maya project direc­tory will help to keep ev­ery­thing or­gan­ised. 09
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 ??  ?? 15 re­al­is­tic ma­te­ri­als in Arnold For more re­al­is­tic ma­te­ri­als you can use the Arnold Stan­dard Sur­face shader, as it al­lows dif­fer­ent at­tributes to cre­ate a va­ri­ety of sur­faces.
15 re­al­is­tic ma­te­ri­als in Arnold For more re­al­is­tic ma­te­ri­als you can use the Arnold Stan­dard Sur­face shader, as it al­lows dif­fer­ent at­tributes to cre­ate a va­ri­ety of sur­faces.
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 ??  ?? check the Arnold light man­ager View sim­ple set­tings for all the lights used in a scene by us­ing the Arnold Light Man­ager. This al­lows you to quickly change some set­tings for the lights. Choose Arnold>util­i­ties> Light Man­ager.
check the Arnold light man­ager View sim­ple set­tings for all the lights used in a scene by us­ing the Arnold Light Man­ager. This al­lows you to quickly change some set­tings for the lights. Choose Arnold>util­i­ties> Light Man­ager.
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