You can use both "generator" and "vdb" to make a cloud in Octane. In this section we will use both to make clouds. Here you can download the mini tutorial scenes from the link below.
Download the "Cloud_01" scene from here
Making volumetric cloud from VDB file
01- Open the "Cloud_01" scene. When you open the scene you will see only the Octane Camera. Do not play with the camera settings for now. Create "Octane VDB Volume" from the Live Viewer Object menu. Load the "cloud_bed_003.vdb" file from the file section. This VDB file should be in the "Tex" folder in the scene you downloaded.
Change the parameters as you see in the picture below. If you look in the info box after loading the VDB file, you will see that the "Density" channel is used when creating this cloud. We will then adjust this volume reference for absorption and scatter in the Volume Medium. Density in Emission mapping is not a problem because we will not use emission in volume medium.
Info: The vdb file on this scene is taken from Travis Davids' "Free VDB cloud Package".
02- Now create an Octane Daylight and change the settings and coordinates as you see in the picture below.
03- Create an HDR environment from Live Viewer/Objects menu. Load the "05-01_Sun_D.hdr" picture in the "Tex" folder of the downloaded scene file and change the settings as you see in the picture below.
04- Now select VDB Volume from object manager and go to the Medium Tab. Add "Volume medium" from octane textures to Volume Medium slot.
05- Click on to the Volume Medium and change the volume parameters as shown in the picture below.
06- Now run Live Viewer. If you have done everything right, you will get the following result. As you can see in the picture, there is a fairly massive cloud in the foreground an it is matched to the HDR image. For such a cloud mass we kept the density high while we decreased Step Length. The important thing here is the Scattering parameter. In reality, even if they are very small, the clouds are optically thick. This will cause the clouds to scatter a significant amount of sunlight; in other words, the probability that the sun will pass through the cloud without being scattered is very weak. Clouds are also weak absorbers of the sunlight at the same time. As a cloud grows, the percentage of sunlight that it reflects increases.
The cloud in the picture absorbs little light. By changing this value you can make the cloud darker (you can, for example, make a rain cloud). Octane Daylight was set up to provide the necessary illumination to the cloud with the HDR image.
Making volumetric clouds usING GENERATe (not SO realISTIC but fast)
In this mini tutorial we will produce a volumetric cloud that is not so realistic but yields fast results. We will make this using noise from the "Generate Tab" section. We will produce the scene from scratch. So we did not provide a download link. If you're ready, let's start.
01- Create Objects/Octane Fog Volume from the Live Viewer menu. Then select the volume from the object manager and go to the "Generate" tab. From there, assign Cinema 4D noise to the texture section and change the settings as you see in the picture below.
Info: You can increase your Voxel size (editor) to work comfortably (eg 5). Then you can decrease to 2 or 3 in final render. Be very careful as you enter fewer than 2 and go with very small steps because as you said before, the number of voxels increases considerably and GPU ram is consuming rapidly. Crash probability is increasing.
02- Click on Cinema 4D Noise in the Texture slot and change the settings as you see in the picture below. With this noise texture we have created the cloud voxel.
04- Now create an Octane Camera and change both the coordinates and parameters as you see in the picture below.
05- Now let's make the lighting for the cloud. To do this, create Objects/Lights/Octane Daylight from the Live Viewer menu and change both the parameters and the coordinates as you see in the picture below.
06- From the Object Manager, select the "Volume" object and go to the Medium Tab. Add "Volume medium" from octane textures to Volume Medium slot.
07- Click on "Volume Medium" and change the volume parameters as you see in the picture below.
08- Now run Live Viewer. If you have done everything right, you will get a result similar to the following picture. As you can see in the picture, after we set the noise texture of Cinema 4D as Voxel input, we made shading from Volume Medium. You can animate this cloud by entering "Animation Speed" in the noise settings. Or you can create another type of cloud by changing the Noise Type. The number of cloud types you will create using Generate is endless. If you keep the voxel size at reasonable levels, you will get a quick render.