Basic usage

Overview

Altus Denoiser uses information from two rendered images to generate a high quality denoised image. This guide will explain how to setup and render the inputs to Altus. There are two concepts that Altus uses to generate denoised outputs:

AOVs (Arbitrary Output Variables) provide a way to render any arbitrary shaded component into different images. Typically renderers will only produce a final color for each pixel of the image (known as the beauty pass, or RGB pass), but you can break out renders into their component parts such as indirect lighting, diffuse color, reflections, shadows, mattes, etc. and save them as files individually or layers as part of a multichannel/multilayer EXR. See Recommended AOVs for more information.

Two images (called buffers) must be generated for each image. It’s important that each buffer is rendered with a different sample seed so that they will have unique noise patterns. The variance between the two buffers is what Altus uses to remove noise. Without variance, there is not enough information to remove noise. See Buffers for more information.

For information on how to run Altus once the correct inputs have been created see Usage.

This guide will explain how to denoise a given scene and adjust some filter settings. Start by downloading the demo scene we will be using: <link will be posted soon>

Demo Contents

The demo scene zip contains two folders of images: b0 and b1. Each folder was rendered with a different seed to ensure that b0, b1 have different noise patterns. Each folder contains all the render passes (AOVs) recommended by Innobright: Recommended AOVs. We will be using these contents to denoise the beauty images.

One of the beauty render (b0):

../../../_images/b0.png

Denoise the Demo Scene:

To start lets denoise the demo scene using default Altus settings. First ensure that Altus has been setup properly.

Setting up the config file

The easist way to run Altus is by using a config file. Config files (.cfg) allow us to define the image paths along with any filter settings. In this guide we will be using a config file. For more info see Configuration Files.

First to define in a config file are the paths to the b0, b1 renders. Lets start with the beauty:

For example:

rgb-0=C:\Example\Files\Pass 1\scene_render.exr
rgb-1=C:\Example\Files\Pass 2\scene_render.exr

Now we can add the position pass and normals:

pos-0=C:\Example\Files\Pass 1\scene_render_worldPosition.exr
pos-1=C:\Example\Files\Pass 2\scene_render_worldPosition.exr

nrm-0=C:\Example\Files\Pass 1\scene_render_normals.exr
nrm-1=C:\Example\Files\Pass 2\scene_render_normals.exr

Finally, we rendered out an AOV for reflections. Lets add that as an extra AOV to Altus. You can add as many extra AOVs to Altus, each AOV will increase the denoise quality:

extra-0=C:\Example\Files\Pass 1\scene_render_reflections.exr
extra-1=C:\Example\Files\Pass 2\scene_render_reflections.exr

Now that we defined all the input images, we should specify where the output will be saved. There are a couple options for that, we will append ”–out-dir” to the config file:

out-dir=C:\tmp\output

All together the final config file should look like:

rgb-0=C:\Example\Files\Pass 1\scene_render.exr
rgb-1=C:\Example\Files\Pass 2\scene_render.exr
pos-0=C:\Example\Files\Pass 1\scene_render_worldPosition.exr
pos-1=C:\Example\Files\Pass 2\scene_render_worldPosition.exr
nrm-0=C:\Example\Files\Pass 1\scene_render_normals.exr
nrm-1=C:\Example\Files\Pass 2\scene_render_normals.exr
extra-0=C:\Example\Files\Pass 1\scene_render_reflections.exr
extra-1=C:\Example\Files\Pass 2\scene_render_reflections.exr
out-dir=C:\tmp\output

Running Altus

Now that we have a config file, we can use it to run Altus. Note: if we dont specify any settings then Altus will use its default values.

To run Altus; first open a CMD/shell window and start Altus by typing the command in this form: <path/to/Altus.exe> –config=<path/to/config.cfg>

My command:

> C:\Program Files\Altus Denoiser\bin\altus-cli.exe --config=C:\tmp\example.cfg

Altus should begin to filter. Once it has completed the output image will be saved in the directory we specified with out-dir.

My denoised result:

../../../_images/altus.png

Basic Filter Settings:

Once you are confortable running Altus, you can expirement with the filter settings. See also Advanced usage for more options. The essential basic settings are as follows:

--radius or -r

Specifies the dimension of the filtering window. The default of 10 means that the origin pixel, plus 10 pixels up, down, left, and right will be considered. That is, the filtering window will be a 21x21 box.

Decreasing the radius will result in faster denoising, but may leave more noise behind.

Increasing the radius will result in significantly slower denoising, possibly removing more noise at the risk of “over-smoothing” an image.

Generally, reducing the radius will be more noticeable visually than increasing it.

--kc_1

This value scales how much color (beauty) will influence the small (detail) kernel blur. Low values will expose more detail at the risk of leaving noise behind.

--kc_2

This value scales how much color (beauty) will influence the large (edge) kernel blur. Low values will expose more detail at the risk of leaving noise behind.

--kc_3

This value is not used; it is present for legacy compatibility.

--kc_4

Controls removal of residual noise.

--kf

Controls the influence of feature AOVs (e.g. position, normals, etc) for all kernel sizes. Generally controls the trade-off between preserving edges and fine detail. Low values will expose more detail at the risk of leaving noise behind.

Denoise Again With Adjusted Filter Settings

Now that we understand the settings, lets try to change the settings on the image we denoised above. Using the config file we created as a starting point, lets change the kc values and window radius to the config file:

kc_1 = 0.25
kc_2 = 0.25
kf = 0.3
radius = 6

Finally the entire config file should look like:

rgb-0=C:\Example\Files\Pass 1\scene_render.exr
rgb-1=C:\Example\Files\Pass 2\scene_render.exr
pos-0=C:\Example\Files\Pass 1\scene_render_worldPosition.exr
pos-1=C:\Example\Files\Pass 2\scene_render_worldPosition.exr
nrm-0=C:\Example\Files\Pass 1\scene_render_normals.exr
nrm-1=C:\Example\Files\Pass 2\scene_render_normals.exr
extra-0=C:\Example\Files\Pass 1\scene_render_reflections.exr
extra-1=C:\Example\Files\Pass 2\scene_render_reflections.exr
out-dir=C:\tmp\output
kc_1=0.25
kc_2=0.25
kf=0.3
radius=6

And the denoised output:

../../../_images/altus.png

Final Notes

Congratuations on completing the basic usage tutorial for Altus Denoiser! If want to tweak Altus to perfection, see: Advanced usage.

Note

Explore our help site for more information on Altus and using Altus with third party software. Here are some places to get started:

For information on Altus CLD Animation.

For information on Altus CLD Output Options.

For information on Altus Studio Basic usage.

To use Altus with other software see: Integration with Third Party Software.