Table of Contents

This tutorial shows the steps needed to generate a Gaussian splat and render it with V-Ray for Cinema 4D.


Generating a Gaussian Splat File

Gaussian Splatts take information from a series of panning images or videos of a scene or object and convert it into a 3-dimensional point cloud. The point cloud is then converted into Gaussians, which can hold information like size, color, and transparency. These Gaussians are then optimized until they are photorealistic, but they remain very light to render.


As a first step, you will need images or footage of a scene or object panning around at a moderate speed. For this tutorial, we have used the bicycle footage in the 3D Gaussian Splatting for Real-Time Radiance Field Rendering paper.

You need to import the materials into software that generates Gaussian Splat files. There are numerous out there, but we have used postshot.

Download the footage from the paper and import it (either as is or converted into separate images) in postshot.

You can leave the settings at their default. They will produce a good result. Click Import to start the training.


Click on the image to view it in full size.



Here is how the 3D scene looks after it is done.






Once the training is done, go to the File menu and select Export Splat Model... This exports only the model, which is what we need. We will add cameras within V-Ray for Cinema 4D.

Name the .ply file, select a destination, and click Save.


Click on the image to view it in full size.



Rendering with V-Ray for Cinema 4D

Open Cinema 4D. In the Render Settings, set the Renderer to V-Ray.

Go to the V-Ray menu > Geometry and select the V-Ray Gaussians.


Click on the image to view it in full size.


Load the generated .ply file to the Gaussians geometry. Click on the icon and select the file we just exported.

It imports with a very small Scale - 1cm. Increase it to around 100 cm.

The axes of postshot are positioned differently from Cinema 4D. Thus, we need to adjust them to match Cinema 4D's environment. Set Flip Axis to Rotate XZ + Flip Y. 



This is how the V-Ray Gaussians look in the Cinema 4D viewport.



Navigating the scene this way is not easy. Let's reduce the radius of the point cloud. In the Gaussians' settings set the Point Radius to 0.003. Leave the rest of the Preview settings as they are.



Now we can zoom in, and the bicycle is distinguishable from the scene. This allows us to better position our camera, without needing to render the scene.




Add a Camera

Let's create a camera for our scene. If your viewport is positioned like in the previous step - looking at the bicycle, when you go to the V-Ray menu > Cameras > Physical Camera, the camera inherits the same position (with an applied V-Ray Physical Camera tag). This is a good way to easily set up your camera view.

Here is our viewport preview and the rendered image.


render Before image
viewport After image


For reference, the camera in this particular render is placed at these coordinates:

  • P.X = 461 cm
  • P.Y = -43 cm
  • P.Z = 309 cm
  • R.H = 109 °
  • R.P = -1 °


Add Geometry

Let's now add two people talking in our scene. We will use the Chaos Cosmos Browser's library. 

  • Firstly, we will add Herbert Standing 001. Download and import the asset into the scene.
  • The asset is a bit small. Select the Cosmos geometry and, in the Coordinates tab, set the S.X, S.Y., and S.Z. to 2.
  • Then, we need to place it so it 'belongs' in the scene. Again in the Transform properties, set:
    • P.X = -390 cm
    • P.Y = -200 cm
    • P.Z = 577 cm


Click on the image to view it in full size.



Then, we will add the second person standing and talking.

  • Add Elbert Standing 002. Download and import the asset into the scene.
  • This asset requires the same resizing as the previous one. Select the geometry and set the S.X, S.Y., and S.Z. to 2, in the Coordinates tab.
  • Then, we need to place it so it 'belongs' in the scene. Again in the Transform properties, set:
    • P.X = -378 cm
    • P.Y = -200 cm
    • P.Z = 404 cm
  • We need to rotate this person so they are facing towards their counterpart. Set R.H. to -170°.


Click on the image to view it in full size.

Add Light

To preview geometry added to the Gaussian Splatts, you need to add a light.

This scene is very cloudy, a soft atmospheric light would be ideal. Add a Dome light. This will serve as our final render light.

Leave the Dome light settings at their default. 

Remember that the Gaussians geometry has light baked into it, but it does not emit any of that light. You always need to add a light source when adding additional geometry to a scene.





This is how the viewport render looks.





To change the viewport used for rendering, click on the View menu in the selected viewport's toolbar and enable Use as Render View.



Add Shadow Catcher

We now have geometry in our scene, but it does not look as if it 'belongs' in the scene. Let's add a Shadowcatcher object under our two people talking to add realism. Create a Plane geometry and place it under the Cosmos assets. In this case, the needed coordinates are:

  • P.X = -381 cm
  • P.Y = -171 cm
  • P.Z = 576 cm





Next, Select the Plane and click on the V-Ray menu > Tools > Make Shadow Catcher. This tool automatically sets all the matte properties needed to transform the selected object into a Shadow catcher.

Read more on the Make Shadow Catcher page.





Camera Setup

The current camera settings create a too-narrow preview; let's increase the field of view.  Go to the Physical Camera tag. In the General tab, set the Focal Length (mm) to 31.

If you need to adjust both the Focal Length (mm) and the Film Gate (mm) parameters, it is easier to use the Field of View property, as its value overrides both these parameters. However, we don't need further adjustments, and in this case, we don't need to use the Field of View property.


We are only lighting the scene with a Dome light. Thus, to achieve proper lighting, we need to increase the camera's light sensitivity. Increase the Film Speed (ISO) value to 400.


Click on the image to view it in full size

Let's now make animate a slow pan of the camera through our scene. Go to the camera objects, and open its Coordinates tab, and set the R.H parameter to 109°. Make sure your Timeline is set to frame 0. Click on the icon next to the R.H parameter. We will be changing the value of this property over time. When the icon becomes red, this means that that property is set to the current value for the current frame. 


Click on the image to view it in full size



Then, go to frame 45 in the Timeline and set R.H to 90°.  Now, if you pan through the timeline, you can see how the camera moves throughout the animation.


Render

All we need to do now is render our animation. This will take a while, as every separate frame needs to be rendered. Consider using Chaos Cloud to speed up the process. 

Remember to set the Output Frame Range to Manual and set the range From 0 To 45. This way, when you begin a render, it will render out the entire animation.




Here is how the final animation looks. Remember, there is no actual geometry in this scene besides the two people talking. Using Gaussian Splatts, we can create entire scenes without much work. Try it yourself - create a scene for your next project using V-Ray Gaussians!




Reference




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