STEP BY STEP: Discover the power of Renderman 22
Follow along to see how this homage to the walking teapot was created with the help of Renderman 22
Master the new Renderman 22
The purpose of a praxinoscope is to create an optical illusion as it spins, causing a series of static drawings to appear to animate. The Renderman Walking Teapot proved to be a good subject for this particular rendition of a praxinoscope by making a series of 12 sculpts appear to walk. Created to function as a real object, this CGI prototype was built with Autodesk Maya, Substance Painter and the new release of Renderman 22. This tutorial shows the power found in Renderman’s impressive new levels of interactivity, so now you can work directly in the renderer from modelling all the way through to final lighting. We’ll also look at interesting techniques for look development, light set-up and how to make sophisticated photorealistic images fast and effectively with Renderman 22.
You can work directly in the renderer from modelling all the way through to final lighting
01 Walk this way A good walk cycle is an essential requirement. first, create a 12-frame walk cycle (ours was made by rotoscoping åa video of a real walking teapot in Maya). next, we’ll use that cycle to generate a series of 12 static teapots, placed around the origin. To validate the cycle it’s just a matter of key framing the group of teapots to make a full rotation once every second. It’s simple to play the animation in Maya and adjust as needed (with Maya’s frame Rate set to 24fps and Playback Speed to 24fps x 0.5) until we have our walking teapot.
02 Position the mirrors Placement of mirrors is important if we want a properly functioning praxinoscope. fortunately, the new IPR in Renderman 22 makes that simple, allowing the creation, positioning and editing of geometry so we can see exactly how the reflection looks in interactive time. In fact, we can start up Renderman in the Maya viewport, and then it’s just a matter of creating a polygonal cylinder with 12 sides (you’ll want to add hard edges), attaching a Mirror shader (you’ll find one in Renderman’s Preset Browser) and editing the geometry until the result is perfect. fast and easy, just how we like our CGI.
03 It’s not old… it’s vintage! for art direction, the goal is to create something that wouldn’t have looked completely out of place in 1876, the year the praxinoscope was invented, meaning old-fashioned components made of worn metal, painted metal and glass. As with the mirrors, build everything during an IPR session to get final-pixel feedback on how the models will look. Use the Renderman Preset Browser to quickly try out various looks on objects. We’ll add a base, roof, rails and planks to the praxinoscope and a magnifying glass and floor to the scene.
04 Look development with substance To create the appearance of a vintage object we’ll need to make the surfaces look aged and worn. Substance Painter is a fantastic tool for creating these types of looks using a combination of proceduralism, textures and surface topology. To do this you’ll want to install the Renderman for Substance Painter plugin written by Philippe leprince, which you can find here: github.com/pleprince/rfsp. This plugin allows you to create shaders in Painter and export them directly to your Renderman Preset Browser, making the process straight-forward. however, the shaders usually require some further tweaking for best results.
05 Two lobes are better than one Renderman ships with the advanced Pixar Surface shader. Pixar Surface supports multiple specular lobes, and we’ll use this feature to enhance some of our shaders we exported from Painter. In our examples we have simple surfaces with diffuse, specular and bump. now we will add a second specular lobe, Clear Coat and modify its bump independently to have a value of zero (in the Clear Coat’s Advanced tab). This will make the Clear Coat smooth while the other specular lobe with have bump, giving depth to the surface. fancy, and it’s easiest to see the results in the images.
06 Easy colour variation The real world is full of slight imperfections, and adding these variations to your CGI scenes can make them more believable. The downside of adding variation is that it can make scenes more complex to create and manage. fortunately, we can create complexity non-destructively so you get the best of both worlds… complexity that’s easy to manage. In this example we will add colour variation to the planks. Simply plug a pxrvary node into the colour of the shader and begin tweaking parameters, and remember you can see the updates immediately in your IPR session.
To create a vintage object we’ll need to make the surfaces look aged and worn. Substance Painter is a fantastic tool for creating these types of looks using a combination of proceduralism, textures and surface topology
07 Different textures for teapots The paint on each teapot is worn, but we don’t want them all to have the same worn pattern. At the same time, it’s easier to manage with one teapot shader. We can do both. Attach our shader from Substance Painter to all the teapots – one for the body and one for the lid – and then randomly assign different texture sets to each object by adding the node pxrmultitexture. The node pxrmultitexture (connected to a pxrtilemanifold) allows up to nine textures to be randomly assigned to different objects based on name, id or primvar. now it’s easy to add more texture variations, or change them completely.
08 Vary hue with primitive variables The next goal is to have the teapots transition from red to yellow for a cool effect when animated. Instead of attaching multiple shaders, we can do this with the same Pixar Surface (one for the body and one for the lid). Add a pxrhsl node (hue, Saturation and luminance) to the teapot’s Diffuse Color, and feed the pxrmultitexture into it. next connect a pxrprimvar node into the value of pxrhsl’s hue. now add a primvar (primitive variable) to the Shape node of each object called ‘hue’ and specify an appropriate hue value, from red to yellow. now one shader will assign a different hue to each teapot.
09 Interactive lighting now it’s time to light the scene. If it isn’t already running, start an IPR session. Because Renderman’s lights and shaders are physically based, one useful thing to do is to create a mirrored sphere, grey sphere and a white sphere in your scene so you can balance the lights and shaders accordingly. Remember surfaces absorb energy, so for the white ball set your Color to RGB=0.8, which is the appropriate setting for white acrylic, and set your grey sphere to RGB=0.18. next add an area light and an environment light (pick one from the Renderman Preset Browser). Tweak until the lighting is blocked in.
Adding variation to these objects is desirable for our final look, but it’s inefficient to add a separate shader to each individual object
10 IES profiles for realism Previously we added subtle variation to our Pixar Surface shaders to make things look more realistic. now we’ll add some realism to our lighting with IES Profiles. You can download your own IES profiles from Philips here: usa.lighting.philips.com. The profile will shape the light in a natural way, giving the lighting subtle characteristics based on the profile. In the area light, load an IES Profile in the light Profile section.
You will see the result immediately in the IPR session. You’ll find advanced controls for IES Profiles in the Renderman Advanced tab of the Render Settings.
11 Create a light filter The light filters in Renderman are the same used in Pixar productions and allow lighting to be creatively directed without having to adjust the lights themselves. It’s another non-destructive workflow. There are several types of filters: Barn Door, Cookie, Gobo, Multi-light, Ramp-light and Rod-light. In this case we’ll add a Rod-light filter to our Area light, so right-click in the light filters field to select a Rod-light. In the other environment light, right-click in the light filters field as well. You’ll see and can pick the filter that was just made. now this Rod-light will affect both lights.
12 Position the filter We’ll take our new Rod-light and move it around in our scene, scaling and adjusting until it surrounds the prax in scope. In the IPR session you’ll see that everything inside the Rod-light is black. To create the effect of a spotlight, toggle Invert so everything outside of the Rod-light is in shadow. Try moving the Rod-light around and changing different parameters to try out different looks; you’ll be able to see the results immediately in the IPR session. Multiple filters can be added to the same light as well. filters offer many ways to sculpt light intuitively and non-destructively.
13 Composition now we have the praxinoscope in all of its glory, fully shaded and lit. for our final rendering we need to compose a shot. To make things more interesting, frame the shot through the magnifying lens. With the IPR session running, move the camera and the magnifying glass and create an interesting composition. If the refraction doesn’t look right, try scaling the lens to increase or reduce the amount of distortion. With immediate feedback in IPR it’s easy to frame this somewhat tricky shot.
14 Pixar Camera To finish up our praxinoscope we’ll add some imperfections to our camera using a custom pxrcamera. Select the Maya Camera and enable Depth of field. Adjust until the Dof is to your liking. next, go to the Renderman tab of the camera. once in the Renderman tab we can toggle enable Camera Projection and right-click on the new field to select pxrcamera. here we can add a vignette to the camera, as well as more complex effects like Tilt Shift Dof, which we can also view in our IPR session. The physical camera controls are capable of creating some unique looks.
15 Render with the Denoiser finally, before rendering an animated sequence enable the Denoiser, which allows images to be rendered with fewer samples for faster renders. The Denoiser runs as a post-process, removing any artifacts. In the new Renderman for Maya, it’s straightforward to denoise specific passes, Aovs and lpes as the Denoiser is now found in the Aovs tab in the Render Settings (just select the Beauty Pass). And that’s how we made our praxinoscope!