Houdini Resources

Updated on June 26  2024



Deborah R. Fowler



Houdini Lighting

Render Basics

This is an extensive topic, but the intention here is just to get you started with a simple scene. There is so much you can do with lights, shaders and rendering in Houdini! There is also a new tutorial by Scott Keating called the Mantra User Guide.

Assigning a shader:

There are two places shaders can be assigned to an object - at the container level - which means everything in that container is affected. (Not the preferred method - it is what happends when you drag a shader to an object for example).

MISSING
        IMAGEThe shader is referenced in the Material parameter in the Render Tab of the container node



MISSING
        IMAGEThe preferred shader assignment is to use a material node in the network and assign the shader in that specific node.

Later on you will also see groups used to assign shaders to groups of objects or even parts of objects, but for now this will get you started.


Shadows:

Lights in Houdini are computed using Ray Tracing. Do not believe outdate forums that say that raytracing is too expensive for shadow computation - it is no longer valid. A few things to mention:
MISSING IMAGE
Here the illumination and the shadow has been turned off on the tube_object1 by the expression ^tube_object1


MISSING IMAGE

The shadow intensity is lessened to .9 allowing light to "bleed" into the shadow area. (As a rule of thumb you should never go below .8)

MISSING IMAGE

Color has been added to the shadow in a very small amount.

This parameter is useful for two things:

Render Tab on the Object Node:

Worth mentioning at this point (although you are likely not to have to use it in a basic set ups) is the Render Tab on each object container node. Here you are able to select objects that you may want to exclude from a reflection or refraction for example.
MISSING
        IMAGEFor light selection use the Data Tree (see section on Light Instancing)


Render Nodes:

 Next, let's take a quick look at the render node - in our case - mantra

MISSING IMAGE
At the top, you can set a Render Frame Range. At first these will be set, delete parameter and set them to the desired value.

You can select Render to Disk (writes to a render folder), Render to MPlay (similar but better than fcheck) or Render to Disk in Background (so you can keep working)

Override Camera Resolution
you should be using all the time. Do not waste time waiting for feedback when you can render smaller and see what you need.


Rendering / Sampling Tab

MISSING IMAGE
Set your Rendering Engine to Physically Based Rendering (PBR)

You will be using this for 99.99999% of renders in mantra. There is a long history here but I will summarize to say that the selections here are a combination of algorithms to compute the shaders/lights and rendered pixels of an image. The most popular method currently is Raytracing with physically based materials and light shaders.

The most common tabs you will use under the Rendering tab are Sampling (shown on the left) and Limits (see below)
For the moment, you may leave the other settings. Those will be discussed in the render optimization section.
Min/Max Ray Samples are usually tweaking before turning up Pixel Samples but we'll discuss later.

You will want to check on Sample Lock.

Rendering / Limits Tab

MISSING
                IMAGEIn the Rendering / Limits tab you will want to turn up Diffuse Limit from the default value of zero to 2.


MISSING
                IMAGEThis example shows that with Diffuse Limit, and a simple Sun/Sky lighting set up, we are getting some color bleed, bounced light and occlusion.

MISSING IMAGEThe difference can be more dramatically seen in this gif toggling between the two.

That brings up two important lighting tools:
  • Squinting (yes squinting)
  • Toggling between subtle changes