PIPE­LINE TECH­NIQUES: Ren­der with Redshift in Hou­dini

Stefan Kang on his op­ti­mum set­tings for Redshift ren­der­ing

3D Artist - - CONTENTS -

in this tu­to­rial you will learn about my process to set up the pri­mary ren­der set­tings us­ing Redshift in hou­dini. We’ll start off by set­ting up a ma­te­rial. Then, we’ll set up par­ti­cle ren­der and cus­tom AOVS. Fi­nally, we’ll ad­just the uni­fied sam­pling to get a pro­duc­tion qual­ity ren­der and set up some ba­sic AOV map for mul­ti­pass com­posit­ing. i’m break­ing it up into a cou­ple top­ics to make sure that i cover as much as pos­si­ble in my set­tings.

My goal is to show you the ad­van­tages of us­ing Redshift so you can utilise the GPU ren­der.

i will also cover some im­por­tant fea­tures that will help with your work­flow. i hope this tu­to­rial will en­cour­age you to use Redshift in your own projects.

To ac­com­plish this tu­to­rial, it’s im­por­tant that you have a ba­sic un­der­stand­ing of hou­dini and are fa­mil­iar with ren­der en­gines. The Redshift ver­sion i’m us­ing here is 2.5.51. Please make sure you have the lat­est ver­sion in order to fol­low the tu­to­rial.

01

Ma­te­rial setup Let’s start by set­ting up a sim­ple ma­te­rial be­fore we move into ren­der­ing. here, i’m creat­ing a dis­place­ment ma­te­rial us­ing a colour layer to get the vein de­tails on the sur­face.

To en­able the dis­place­ment tex­ture, you need to add a Redshift Ob­ject pa­ram­e­ter on the SOP level of the ge­om­e­try. Then find the Tes­sel­la­tion/dis­place­ment tab to en­able the dis­place­ment. it’s more ef­fi­cient to use the Redshift na­tive cat­mull-clark tes­sel­lated sur­faces, be­cause the ex­trac­tion time will be lower and the fi­nal ge­om­e­try is more GPU mem­ory ef­fi­cient.

Then i use a tex­ture im­age over the colour layer as a mask to cre­ate dif­fer­ent veins and con­trol their colour. The rea­son i’m us­ing the blend­ing mode to cre­ate the vein is be­cause i want to be able to fully ma­nip­u­late its po­si­tion in ren­der­ing, so it can be ap­plied on dif­fer­ent shapes of ge­om­e­try. next, go to the sub­sur­face sec­tion, ap­ply the trans­mit­tance colour and set the ab­sorp­tion scale to 30 with 1 as the scat­ter scale. The higher the ab­sorp­tion scale, the more den­sity in the trans­mit­tance colour.

02

Cus­tom AOV setup next, let’s set up some cus­tom AOVS. This step is handy if you have al­ready gen­er­ated a cus­tom at­tribute to con­trol your ef­fects. i of­ten like to do this be­cause i can cre­ate my own cus­tom RGB layer and out­put it into the AOV map. This way the com­pos­i­tor will be able to fur­ther con­trol the

ef­fects us­ing the AOVS. Go to the ma­te­rial net­work and add a Rs colour user data node. This node will al­low you to im­port the at­tribute and store it un­der the ma­te­rial. Then you’ll need to go to the Redshift ROP out­put un­der the AOV tab and cre­ate a cus­tom AOV chan­nel. name the at­tribute name un­der the Redshift ROP out­put. it’s im­por­tant to make sure the AOV name and the at­tribute name are the same. Keep in mind that there are a cou­ple of dif­fer­ent types of data. My at­tribute is mainly RGB colour (float value) re­lated, so i’m only us­ing the store­colour To AOV node. if you are look­ing to ex­port scalar or in­te­ger value, then you should use the other rel­e­vant node to store the value (the node i dis­abled).

03

Par­ti­cle ren­der­ing now we will set up a Par­ti­cle ren­der in Redshift. By de­fault, the Par­ti­cles won’t show up in the ren­der un­less you en­able them. To en­able Par­ti­cle ren­ders in Redshift, use the op­tion avail­able in the Par­ti­cles of the Redshift OBJ spare Pa­ram­e­ter and make sure to en­able Ren­der Ob­ject as Par­ti­cles. By de­fault, un­der Redshift OBJ> at­tributes, the au­to­matic at­tribute ex­trac­tion is en­abled. i usu­ally turn it off and spec­ify the only at­tribute i need to use. This will help op­ti­mise the mem­ory. now i’m al­low­ing the use of this at­tribute un­der ma­te­ri­als to con­trol the shader. For this par­tic­u­lar project, i’m us­ing the pscale> Rs­math­range (it’s sim­i­lar to a fi­trange) to remap the dif­fuse and re­flec­tion, so the re­flec­tiv­ity will be var­ied based on the size of the par­ti­cle.

04

Ren­der setup – uni­fied sam­pling now we will set up the sam­pling in the Redshift ren­der set­tings. The uni­fied sam­pling in Redshift is de­signed to han­dle AA, depth of field, mo­tion blur and so on.

There­fore, it’s im­por­tant to set the lo­cal sam­ples (spec­u­lar, Re­frac­tions, Brute Force Gi, Lights, AO) higher than the max sam­ple. it’s rec­om­mended to have lower set­tings for the adap­tive thresh­old like 0.003, to get pro­duc­tion qual­ity re­sults. here i am us­ing 4 minimum sam­ples and 512 max­i­mum sam­ples. The sam­ple set­tings here are what i found best for this project, but be aware that dif­fer­ent en­vi­ron­ments re­quired dif­fer­ent sam­ples for a bet­ter re­sult. i also cre­ated a cou­ple of ma­te­ri­als like AO, Point Po­si­tion pass, uv pass for bet­ter con­trol in post com­posit­ing.

05

Set up Brute Force and ir­ra­di­ance cache next we will jump into set­ting up the Gi en­gines. For this shot, i’m fo­cus­ing on us­ing Brute Force as the Pri­mary Gi en­gine and ir­ra­di­ance Point­cloud for the se­condary. This way the ir­ra­di­ance Point­cloud will help the Brute Force en­gine to solve the ar­eas that are harder to solve by av­er­ag­ing the pixel colour vari­a­tion. This process will use the se­condary Gi en­gine for mul­ti­ple bounces. if you com­pare the two, you will no­tice the ar­eas with noise now be­come smoother.

06

Mul­ti­pass com­posit­ing Lastly, we will be set­ting up the AOV passes so we can do a beauty re­build in the com­posit­ing stage and make fi­nal tweaks and con­trols to your im­age. i love do­ing this be­cause a lot of the time you will need to re-ad­just colour grad­ing or add some 2D ef­fects like glow or depth of field and mo­tion blur to en­hance the com­po­si­tion. All the AOV passes i’m us­ing to re­build are: dif­fuse fil­ter, dif­fuse light­ing raw, global il­lu­mi­na­tion raw, sub­sur­face scat­ter­ing raw, spec­u­lar light­ing, re­flec­tions, re­frac­tions, caus­tic, emis­sion, mo­tion vec­tors, Zdepth. The im­age on step 6 shows you how i put to­gether the passes with dif­fer­ent blend­ing modes with nuke be­ing used for coloura­tion to Lin­ear, which is ef­fec­tively dis­abling the cs set­tings for that im­age. nor­mal maps es­pe­cially should never be colour cor­rected, as their colour val­ues are for con­trol­ling nor­mal di­rec­tion, so chang­ing them will up­set your nor­mal. Any colour tex­tures should of course be colour man­aged, and set to the de­fault SRGB, to match SRGB dis­plays cor­rectly.

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