Basic displacement in RenderMan /  by Xuan Prada

  • Select the object’s shape node in the Attribute Editor and then go to Attribute -> RenderMan -> Add Sudvision Scheme. This will create a smooth surface.
  • Load your displacement texture in the Hypershade.
  • Play with the Alpha Gain and Alpha Offset to scale the image.
  • Alpha Offset should be half negative than Alpha Gain. So if Alpha Gain is 2 Alpha Offset should be -1
  • Drag the displacement texture on to the displacement material in the shading group attributes.
  • This will create a displacement node.
  • Select the displacement node and go to Attributes -> RenderMan -> Add Displacement Attribues.
  • Set the displacement bound to something similar to your highest displacement value.
  • If you are using ray trace rendering you need to add ray traced attributes to your displacement.
  • Select your shape node and go to Attribute -> RenderMan -> Manage attributes and select TraceDisplacement.
  • Turn the shading rate down to increase the quality of your displacement. You can add a RenderMan attribute to control this instead change the global render options, you’ll save a lot of render time.

Linear Workflow in Maya with Vray 2.0 /  by Xuan Prada

I’m starting a new work with V-Ray 2.0 for Maya. I never worked before with this render engine, so first things first.
One of my first things is create a nice neutral light rig for testing shaders and textures. Setting up linear workflow is one of my priorities at this point.
Find below a quick way to  set up this.

  • Set up your gamma. In this case I’m using 2,2
  • Click on “don’t affect colors” if you want to bake your gamma correction in to the final render. If you don’t click on it you’ll have to correct your gamma in post. No big deal.
  • The linear workflow option is something created for Chaos Group to fix old VRay scenes which don’t use lwf. You shouldn’t use this at all.
  • Click on affect swatches to see color pickers with the gamma applied.
  • Once you are working with gamma applied, you need to correct your color textures. There are two different options to do it.
  • First one: Add a gamma correction node to each color texture node. In this case I’, using gamma 2,2 what means that I need to use a ,0455 value on my gamma node.
  • Second option: Instead of using gamma correction nodes for each color texture node, you can click on the texture node and add a V-Ray attribute to control this.
  • By default all the texture nodes are being read as linear. Change your color textures to be read as sRGB.
  • Click on view as sRGB on the V-Ray buffer, if not you’ll see your renders in the wrong color space.
  • This is the difference between rendering with the option “don’t affect colors” enabled or disabled. As I said, no big deal.

Physical Sun and Sky and Linear Workflow /  by Xuan Prada

  • First of all activate Mental Ray in the Rendering Options.
  • Create a Physical Sun and Sky system.
  • Activate Final Gather. At the moment should be enough if you select the Preset Preview Final Gather. It’s just for testing purposes.
  • Check that the mia_exposure_simple lens shader has been added to the camera. And Check that the gamma is set to 2.2
  • Launch a render and you’ll realize that everything looks washed.
  • We need to add a gamma correction node after each texture node, even procedural color shaders.
  • Connect the texture file’s outColor to the “Gamma Correction” node’s value. Then connect the “Gamma Correct” node’s outValue to the shader’s diffuse.
  • Use the value 0.455 in the gamma node.
  • The gamma correction for sRGB devices (with a gamma of approximately 2.2) is 1/2.2 = 0.4545. If your texture files are gamma corrected for gamma 2.2, put 0.455 into the Gamma attribute text boxes.
  • If you launch a render again, everything should looks fine.
  • Once you are happy with the look of your scene, to do a batch render you need to put the gamma value of the lens camera shader to 1.
  • Under the quality tab, in the framebuffer options, select RGBA float, set the gamma to 1 and the colorspace to raw.
  • Render using openExr and that’s it.

Mari to Maya /  by Xuan Prada

Yes I know, make your Mari textures work inside Maya could be a bit weird specially if you never worked before with multi UV spaces.

I hope to give you some clues with this quick and dirty step by step tutorial.

I’m using the blacksmith guy from The Foundry who has 40 textures with 4k resolution each.

  • First of all check your model and UVs.
  • Export all your textures from Mari. You know, right click on the desired channel and export.
  • Now you can type the naming convention that you want to use. I like to use COMPONENT_UDIM.tif COL_1001.tif for example.
0003.png
  • Check your output folder. All your textures should have been exported.
  • Import your model in Maya and check the UV mapping. You need to understand how the UV shells are called inside Maya to offsetting your texture maps.
  • The default UV space is 0-0 the next one on the right will be 0-1 the next one 1-1 and so on.
  • Open the first texture map called COL_1001.tif in the hypershade and rename the image node to COL_1001 and the 2D placement node to UDIM_1001.
  • Do the same with all the textures.
  • Select all the texture nodes and open the attribute spread sheet.
  • Set the default color RGB to 0.
  • Select all the 2D place texture nodes and open again the attribute spread sheet.
  • Switch off wrapU and wrapV.
  • Type the properly offsets in the translate frameU and translate frameV.
  • Create a layered texture node.
  • Select all the texture images nodes and click and drag with MMB from an empty space of the hypershade to the layered texture node attributes tab. This will create one layer with each texture map.
  • Delete the default layer.
  • Set the blending mode of all the layers to lightnen.
  • Connect the layered texture to the input color of one shader of your election.
  • Repeat the whole process with all your channels. (SPEC, BUMP, DISP, etc)

Mari to Softimage /  by Xuan Prada

Recently I was involved in a master class about texturing and shading for animation movies, and as promised I’m posting here the technical way to set-up different UV sets inside Softimage.
Super simple process and really efficent methodology.

  • I’m using this simple asset.
  • These are the UVs of the asset. I’m using different UV sets to increase the quality. In this particular asset you can find four 4k textures for each channel. Color, Specular and Bump.
  • You probably realized that I’m using my own background image in the texture editor. I think that this one is more clear for UV mapping than the default one. If you want you can download the image, convert it to .pic and replace the original one located on C:\Program Files\Autodesk\Softimage 2012\Application\rsrc
  • This is the render tree set-up. Four 4k textures for color, specular and bump. Each four textures are mixed by mix8color node.
  • Once everything is connected, you still need to offset each image node to match the UV ranges.
  • I know that the UV coordinates in Softimage are a bit weird, so find below a nice cart which will be so helpfull for further tasks.
  • Keep in mind that you should turn off wrap U and wrap V for each texture in the UV editor.
  • Really quick render set-up for testing purposes.

Faking SSS in Softimage /  by Xuan Prada

SSS is a very nice shader which works really great with a good lighting setup, but sometimes  is so expensive shader when you´re using Mental Ray.
Find below a couple of tecniques to deal better with SSS. Just keep in mind that those tricks could improve your render times a bit, but never will reach the same quality than using SSS for itself.

  • I’m using this simple scene, with one key light (left), one fill light (right) and one rim light.
  • A SSS compound is connected to the material surface input, and the SSS_lightmap (you can find that node in the render tree -> user tools) connected to the lightmap input of the SimpleSSS. And then, the Simple SSS lightimap connected to the material lightmap input.
  • Write the output and resolution of your lightmap.
  • Hit a render and check the render time.
  • Disconnect the lightmap.
  • Render again and check the render times as well. We have imprpved the times.
  • If you need to really fake the SSS and render so fast, you can bake the SSS to texture using RenderMap, but keep in mind that the result will be much worst than using SSS. Anyways you can do that for background asset or similar.
  • Now you can use another cheaper shader like blinn, phong or even constant with your baked SSS.
  • As you can see the render is now so fast.