This page provides a step-by-step guide to optimizing V-Ray render settings.
In this tutorial we will optimize the render settings and use targeted sampling in order to speed up the render times.
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1) Set up the Adaptive Sampling
We start with the scene set up as per the end of the QuickStart Intro, with the Adaptive sampler used to clear up the noise by using a Min shading rate of 16, and 16 Max subdivs.
In order for the sampling to be used in a more targeted manner, you need to reduce the Min shading rate to 1, and the Max subdivs to 4. This means that the Adaptive sampling will be focusing on antialiasing over GI and reflections. It will also fire far fewer samples. We can target the samples to where they are most needed.
Do a test render and make a note of the noisy areas. We'll go about updating in the order of materials, lights, and GI. Each problem needs to be tackled in turn, so we will start by looking at materials.
2) Increase Reflection Rays
The biggest problem is the fireflies on the LP covers, so locate both the LP cover materials in the Shader Tree. Set the Reflection Rays to 1024 in the material ref tag.
Next find the Nickel, Anisotropic Steel, and the Earcup materials and set their Reflection Rays to 256.
It will also help to increase the Reflection Subdivs of V-Ray Materials in the scene. To do this, we must first enable the Use Local Subdivs parameter in the DMC Sampler. To access this setting from the Shader Tree, select the Render. In the Properties, go to the V-Ray Main tab and expand the DMC Sampler rollout.
Once Use Local Subdivs has been enabled, select your V-Ray Material from the Shader Tree. You will find that the Reflection Subdivs parameter in the Reflection layer rollout can be edited now. Here, we have increased the default value of 8 to 16.
A test render should reveal that the LP covers are somewhat better but still need improving, and that the metals are still noisy. Since there has been no change in the metals, we can deduce that more reflection rays are not the answer; light samples are the cause of the problem.
3) Increase Light Samples
Select all the area lights in the scene. Then go the to V-Ray Light tab and enable Use V-Ray subdivs. Set the V-Ray Subdivs to 24 and render.
4) Final Material Tweaks
The wooden table is still a little noisy after increasing the samples in the lights, so this means it needs some additional reflection samples. Locate the Table Top material in the Shader Tree and increase the Reflection Rays to 256.
You will notice that there are still a few fireflies on the LP covers, so draw a Render Region in the top right of the frame. Increase the Reflection Rays on the LP cover materials to 8192. A test render should result in much cleaner results without the fireflies.
5) Clean up the DOF AA
There is a also a little noise in the DOF. This is a pure anti-aliasing problem. Draw a render region around the far earcup and return to the Adaptive Sampling settings to increase the Max subdivs to 12.
Do a test render and the results should now be clean.
6) Optimize the Global Illumination
The GI in this scene is not computationally expensive because we have four area lights providing most of the illumination. This means we do not need to use Brute Force for the first bounce. We can set Primary Engine to Irradiance Mapping, then choose the Medium preset from the Irradiance Map quality drop-down menu.
Reduce the number of Subdivs in the Light Cache, which is used for calculating the second bounce, to 500.
These changes should give a small speed improvement. Do a final test render. Note that the render is now both faster and cleaner than the original render which used the Adaptive sampler to brute force the sampling.
When render times are important, optimizing on a case-by-case basis (for each material, light, and for GI) will give cleaner and faster results.