Redshift Volumes in Cinema 4D: OpenVDB, Pyro, Volume Materials and GPU Memory
Clouds, smoke and fire render in Redshift from OpenVDB files or Cinema 4D Pyro. The main points from Maxon's documentation:
- Load the VDB: Create a Redshift Volume object from the Volume menu, set Path, and read the channel names in its Information section.
- Shade with the Standard Volume material: Maxon recommends it over the legacy Volume shader. density drives scattering, temperature drives emission; Pyro has a ready Pyro Volume preset.
- Memory is the hard limit: Volume rendering does not use out-of-core memory, so each volume must fit in the GPU memory of every card that renders it.
- Light it correctly: Volume Trace Depth controls multiple scattering, which only works with Brute Force GI. Light linking and User Data nodes do not work with volumes.
- Rendering heavy simulations: Volumes need memory per card, so iRender servers with RTX 5090 (32 GB per GPU) give the most room; check the volume in the RenderView before rendering the sequence.
Smoke, fire, clouds and explosions are some of the heaviest things you can render on a GPU. This guide covers how Redshift loads OpenVDB files and Cinema 4D Pyro, which material to use, why volumes run out of GPU memory when the rest of the scene does not, and how to light volumes so they do not look flat.
Checked against the Cinema 4D and Redshift documentation, November 2026.
1. How do you render an OpenVDB file in Redshift?
OpenVDB files are to volumes what EXR files are to images: they store voxels, three-dimensional pixels, organised into named grids such as density or temperature. In Cinema 4D you load them with a Redshift Volume object, or a Cinema 4D Volume Loader for better viewport display, and shade them with a volume material (Maxon: Redshift Volume Object).
Settings of the Redshift Volume object
From Maxon's Volume Object documentation.
| Setting | What it does | Tip |
|---|---|---|
| Path | The VDB file or sequence to render. | Keep sequences in the project folder. |
| Mode / Timing | How a sequence plays: Off, Simple, Loop or Ping-Pong, timed by Frame, Time or Range. | Detect Frames fills start and end automatically. |
| Start Offset / Frame Rate | Shift the first file used and set a custom playback rate. | Retime a simulation without re-simulating. |
| Preview / Prune Threshold | Viewport display as bounding box or points; low-value voxels are hidden in Points mode. | Display only; does not change the render. |
| Volume Padding | Expands the bounding box, in voxels, to allow volume displacement. | Large values can increase render times. |
| Velocity Grid X/Y/Z, Velocity Scale | Velocity channels used for motion blur; a single vector grid goes in X. | Velocity Scale often needs large values. |
| Information | Lists the grids (channels) in the loaded VDB. | Use these exact names in the volume material. |
Sources: Maxon Redshift: Volume Object, OpenVDB.
2. How to set up a volume in Redshift (step by step)
Settings checklist (copy or follow line by line):
Volume menu › Redshift Volume Path .................. VDB file or sequence Detect Frames ......... for sequences Information ........... note the exact grid names Material ................ Standard Volume (Pyro: Pyro Volume preset) Scattering ............ density Emission .............. temperature (fire) Lights .................. dome light + key light Check ................... GPU memory in the Redshift Feedback Display
Step 1: Create the volume object
Choose Redshift Volume from the Volume menu, set Path to the VDB file or sequence, and click Detect Frames for a sequence.
Step 2: Check the channels
Open the Information section to see the grids in the file. You will need these exact names.
Step 3: Apply a volume material
Use the Standard Volume material, which Maxon recommends over the legacy Volume shader for better light scattering and volumetric displacement. Connect density to scattering and temperature to emission for fire. For Cinema 4D Pyro, apply the Pyro Volume preset, which already uses density and temperature.
Step 4: Add light that reaches the volume
Volumes need lights to scatter; a dome light and a key light are a good start.
Step 5: Watch memory
Render a test frame and check GPU memory in the Redshift feedback display before rendering the sequence.
Quick check: if the volume renders empty, compare the grid names in the Information section with the channel names in the material; they must match exactly.
3. Why do volumes run out of GPU memory?
Because volume rendering does not use Redshift’s out-of-core system. Textures and geometry can spill into system RAM when a GPU is full; volumes cannot. The figure shows what that means on a machine with more than one GPU.
Redshift renders each frame on all GPUs, but every GPU keeps its own copy of the scene, volume included. So two, four or eight GPUs make a volume render faster, while the largest volume you can render is set by the memory of one card. Maxon notes that too many or very high-resolution volumes can abort the render with an out-of-VRAM error (Maxon: Volume Object).
Illustrative calculation: a fully dense 500 x 500 x 500 grid holds 125 million voxels; stored as 32-bit floats that is about 500 MB for one channel. OpenVDB is sparse, so real files are usually smaller, but every extra channel and every doubling of resolution, which multiplies the voxel count by eight, adds up quickly.
- Simulate at the resolution the shot needs: Maxon notes that resolution matters most for how smooth a volume looks, so spend it where the camera is close.
- Keep only the grids you shade with: export density, temperature and velocity rather than every simulation channel.
- Split large effects: several smaller volumes that are not all in frame at once are easier to fit.
4. How to light volumes so they do not look flat
Clouds and smoke get their soft, bright look from light scattering many times inside the volume. In Redshift that is controlled by Volume Trace Depth in the render settings; Maxon’s examples compare depths of 1, 11 and 31 and recommend raising it slowly as needed (Maxon: Volume Shader).
- Brute Force GI: volume multiple scattering only works with Brute Force global illumination.
- No light linking: volume objects are not compatible with light linking, so control light on volumes with separate lights instead.
- No User Data: User Data nodes do not work with volume shading, so per-object variation must come from the volume grids themselves.
- Motion blur: volumes are stored frame by frame, so motion blur comes from velocity grids set on the Volume object or in the Redshift Object tag.
5. Where should you render volume simulations: SaaS or IaaS farm?
VDB sequences are large and must fit in GPU memory. A SaaS render farm suits a volume whose memory use you already know, uploaded with the full sequence. An IaaS render farm such as iRender lets you copy the VDB sequence to the server, open the scene on the GPUs that will render it, check memory and lighting in the RenderView, and choose RTX 5090 cards with 32 GB per GPU when the volume needs more room.
These videos show Cinema 4D and Redshift jobs on iRender multi-GPU servers.
On iRender you rent a whole server with 2x, 4x or 8x RTX 5090 or RTX 4090 GPUs, with Cinema 4D and Redshift pre-installed; Prime members get activated Cinema 4D and Redshift licenses. Related: Redshift motion blur, including velocity grids and GPU memory per card compared. Real render times are in our Redshift benchmark, and plans are on the Cinema 4D Redshift render farm page.
6. Redshift Volumes FAQ
How do I render an OpenVDB file with Redshift in Cinema 4D?
Create a Redshift Volume object from the Volume menu, set Path to the .vdb file or sequence, then apply a Redshift Standard Volume material and connect the channel names listed in the object’s Information section, such as density for scattering.
Why does my Redshift volume run out of VRAM?
Volume rendering does not use Redshift’s out-of-core system, so the whole volume must fit in GPU memory. Too many or very high-resolution volumes can abort the render with an out-of-VRAM error. Reduce resolution, crop or split the volume, or use a GPU with more memory.
Do more GPUs let me render bigger volumes?
No. More GPUs render each frame faster, but every GPU has to hold the volume in its own memory. A larger volume needs more memory per card, not more cards.
How do I render Cinema 4D Pyro with Redshift?
Apply a Redshift Pyro Volume material preset to the Pyro object. It comes with the density and temperature grids already set for scattering and emission, so you can render right away and then adjust the look.
Why does my smoke look flat or too dark in Redshift?
Light scattering inside a volume is controlled by Volume Trace Depth in the render settings. Raise it gradually for brighter, softer clouds. Multiple scattering in volumes only works with Brute Force global illumination.
Can I use light linking or User Data nodes on volumes?
No. Maxon’s documentation states that volume objects are not compatible with light linking, and that User Data nodes do not work with volume shading.
