Zbrush displacement in Clarisse / January 12, 2015 by Xuan Prada

This is a very quick guide to set-up Zbrush displacements in Clarisse.
As usually, the most important thing is to extract the displacement map from Zbrush correctly. To do so just check my previous post about this procedure.

Once your displacement maps are exported follow this mini tutorial.

In order to keep everything tidy and clean I will put all the stuff related with this tutorial inside a new context called "hand".
In this case I imported the base geometry and created a standard shader with a gray color.
I'm just using a very simple Image Based Lighting set-up.

Then I created a map file and a displacement node. Rename everything to keep it tidy.

Select the displacement texture for the hand and set-up the image to raw/linear. (I'm using 32bit .exr files).

In the displacement node set the bounding box to something like 1 to start with.
Add the displacement map to the front value, leave the value to 1m (which is not actually 1m, its like a global unit), and set the front offset to 0.

Finally add the displacement node to the geometry.

That's it. Render and you will get a nice displacement.

If you are still working with 16 bits displacement maps, remember to set-up the displacement node offset to 0.5 and play with the value until you find the correct behaviour.

Sketch shader / October 17, 2014 by Xuan Prada

First attempt to create a shader that looks like rough 2D sketches.
I will definitely put more effort on this in the future.

I'm pretty much combining three different pen strokes.

Clarisse, layers and passes / September 17, 2014 by Xuan Prada

I will continue writing about my experiences working with Clarisse. This time I'm gonna talk about working with layers and passes, a very common topic in the rendering world no matter what software you are using.

Clarisse allows you to create very complex organization systems using contexts, layers/passes and images. In addition to that we can compose all the information inside Clarisse in order to create different outputs for compositing.
Clarisse has a very clever organization methods for huge scenes.

For this tutorial I'm going to use a very simple scene. The goal is to create one render layer for each element of the scene. At the end of this article we will have foreground, midgrodund, backgorund, the floor and shadows isolated.

At this point I have an image with a 3DLayer containing all the elements of the scene.

I've created 3 different contexts for foreground, midground and background.
Inside each context I put the correspondent geometry.
Inside each context I created an empty image.

I created a 3DLayer for each image.

We need to indicate which camera and renderer need to be used in each 3DLayer.

We also need to indicate which lights are going to be used in each layer.
At this point you probably realized how powerful Clarisse can be for organization purposes.

In the background context I'm rendering both the sphere and the floor.

In the scene context I've created a new image. This image will be the recipient for all the other images created before.

In this case I'm not creating 3DLayers but Image Layers.
In the layers options select each one of the layers created before.
I put the background on the bottom and the foreground on the top.
We face the problem that only the sphere has working shadows. This is because there is no floor in the other contexts.

In order to fix this I moved the floor to another context called shadow_catcher.
I created a new 3DLayer where I selected the camera and renderer.
I created a group with the sphere, cube and cylinder.
I moved the group to the shadows parameter of the 3DLayer.

In the recipient image I place the shadows at the bottom. That's it, we have shadows working now.

Oh wait, no that fast. If you check the first image of this post you will realize that the cube is actually intersecting the floor. But in this render that is not happening at all. This is because the floor is not in the cube context acting as matte object.
To fix this just create an instance of the floor in the cube context.
In the shading options of the floor I localize the parameters matte and alpha (RMB and click on localize).
Then I activated those options and set the alpha to 0%
That's it, working perfectly.

At this point everything is working fine, but we have the floor and the shadows together. Maybe you would like to have them separated so you can tweak both of them independently.
To do this, I created a new context only with the floor.
In the shadows context I created a new "decal" material and assigned it to the floor.
In the decal material I activated receive illumination.
And finally I added the new image to the recipient image.

You can download the sample scene here.

Love Vray's IBL / August 19, 2012 by Xuan Prada

When you work for a big VFX or animation studio you usually light your shots with different complex light rigs, often developed by highly talented people.
But when you are working at home or for small studios or doing freelance tasks or whatever else.. you need to simplify your techniques and tray to reach the best quality as you can.

For those reasons, I have to say that I’m switching from Mental Ray to V-Ray.
One of the features that I most love about V-Ray is the awesome dome light to create image based lighting setups.

Let me tell you a couple of thing which make that dome light so great.

First of all, the technical setup is incredible simple. Just a few clicks, activate linear workflow, correct the gamma of your textures and choose a nice hdri image.
Is kind of quick and simple to reduce the noise generated by the hdri image. Increasing the maximum subdivisions and decreasing the threshold should be enough. Something between 25 to 50 or 100 as max. subdivision should work on common situations. And something like 0.005 is a good value for the threshold.

The render time is so fast using raytracing stuff.
Even using global illumination the render times are more than good.
Displacement, motion blur and that kind of heavy stuff is also welcome.
Another thing that I love about the dome light using hdri images is the great quality of the shadows. Usually you don’t need to add direct lights to the scene. If the hdri is good enough you can match the footage really fast and accurately enough.

The dome light has some parameters to control de orientation of your hdri image and is quite simple to have a nice preview in the Maya’s viewport.

In all the renders that you can see here, you probably realized that I’m using an hdri image with “a lot” of different lighting points, around 12 different lights on the picture. In this example I put a black color on the background and I changed all the lights by white spots. It is a good test to make a better idea of how the dome light treats the direct lighting. And it is great.

The natural light is soft and nice.

These are some of the key point because I love the VRay’s dome light :)
On the other hand, I don’t like doing look-dev with the dome light. Is really really slow, I can’t recommend this light for that kind of tasks.
The trick is to turn off your dome light, and create a traditional IBL setup using a sphere and direct lights, or pluging your hdri image to the VRay’s environment and turn on the global illumination.
Work there on your shaders and then move on to the dome light again.

My favourite V-Ray passes / July 18, 2012 by Xuan Prada

Recently working with V-Ray I discovered that these are the render passes which I use more often.
Simple scene, simple asset, simple texture and shading and simple lighting, just to show my render passes and pre-compositing stuff.

Global Illumination
Direct lighting
Normals
Reflection
Specular
Z-Depth
Occlusion
Snow (or up/down)
Uvs
XYZ (or global position)

Linear Workflow in Maya with Vray 2.0 / May 16, 2012 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.

Faking SSS in Softimage / October 29, 2011 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.

xuan prada