Blender GPU Rendering: CUDA vs OptiX – The Good and The Bad

Blender is a powerful 3D modeling software that allows users to create stunning visual effects, animations, and more.

One of the key features of Blender is its ability to use GPU rendering to speed up the rendering process.

Two popular options for GPU rendering in Blender are CUDA and OptiX.

In this article, we will explore the differences between CUDA and OptiX. We will also determine which one is better for rendering in Blender.

What is CUDA and OptiX in Blender? 

Both CUDA and OptiX are NVIDIA’s GPU rendering technologies that can be used in Blender.

CUDA, short for Compute Unified Device Architecture, is a technology developed by NVIDIA for parallel computing on their graphics processing units (GPUs).

It has been around for a while and has proven to be a reliable and stable solution for GPUs. CUDA works by offloading the processing to the GPU, freeing up the CPU for other tasks. Many applications, including Blender, widely support CUDA.

OptiX, on the other hand, is a newer technology developed by NVIDIA.

It’s a GPU-based real-time ray tracing engine that provides fast and accurate rendering of 3D scenes, making it ideal for rendering high-quality reflections and refractions. OptiX is specifically designed for ray tracing, giving it an advantage over other solutions.

OptiX has the potential to deliver faster rendering times compared to CUDA, especially when using advanced features like AI denoising.

Also Read: The best laptops for 3D modelling: What to look for

CUDA vs OptiX: Is CUDA or OptiX faster in Blender? 

When it comes to rendering speed, both CUDA and OptiX have their advantages.

OptiX has a speed advantage of 60-80% over CUDA when using the same hardware. However, CUDA tends to be faster when rendering simpler scenes or using simpler materials, while OptiX is faster for more complex scenes with lots of reflections and refractions.

OptiX can offer faster rendering times than CUDA in certain scenarios, particularly when it comes to complex scenes that require a large number of rays.

However, this can depend on the specific hardware configuration and rendering engine being used.

In general, it’s recommended to test both CUDA and OptiX rendering on your hardware and compare the performance results to determine which one is faster for your specific use case.

Which one is better for GPU rendering in Blender? 

The answer is not straightforward, as it depends on your specific needs and hardware.

If you have a newer NVIDIA GPU that supports OptiX, then you may see significant performance improvements using this technology.

However, if your GPU does not support OptiX, then CUDA is still an excellent option that will provide reliable and stable rendering performance.

In general, if you have an NVIDIA GPU and you don’t need advanced ray tracing features, CUDA may be the better choice due to its wider compatibility and stability.

However, if you need advanced ray tracing features or you have a non-NVIDIA GPU, OptiX may be a better choice.

Ultimately, the best option will depend on your specific needs and hardware.

Below Bar diagram compares the rendering times for OptiX and CUDA rendering on a GTX 1660 Super GPU and an Intel i7-10700K CPU. You can also see rendering times for OptiX+CPU and CUDA+CPU.

Based on the results, it appears that the combination of OptiX and CPU produced the fastest rendering time for the Blender Classroom scene, followed closely by CUDA+CPU, OptiX alone, and finally CUDA alone.

This is consistent with the general understanding that OptiX is a faster rendering method compared to CUDA due to its real-time ray tracing capabilities.

However, it’s interesting to note that the combination of OptiX and CPU was able to outperform both CUDA and OptiX alone, indicating that CPU processing power can still have a significant impact on rendering times.

It’s worth noting that these results may not necessarily hold true for other scenes or different hardware configurations, and that rendering time is just one factor to consider when choosing a rendering method. Other factors such as image quality, ease of use, and compatibility with other software should also be taken into account.

Should I render with CUDA or OptiX?

 The choice between CUDA and OptiX ultimately depends on your specific needs and the type of project you are working on.

If you are working on a complex scene with lots of reflections and refractions, OptiX will likely be faster. If your scene is simpler, CUDA may be a better choice.

In general, if you have an NVIDIA GPU that supports OptiX, use OptiX for GPU rendering in Blender. OptiX is a newer technology than CUDA and is specifically designed for ray tracing applications.

It generally provides faster render times than CUDA, especially for scenes that have a lot of geometry and require complex lighting and shading.

However, if you are using an older version of Blender that does not support OptiX, you may need to use CUDA. 

Also, if you have a lower-end NVIDIA GPU that does not support OptiX, you may need to use CUDA instead. 

CUDA is a mature technology that has been used for GPU rendering in Blender for many years and is still a reliable and efficient option for rendering.

Ultimately, the best way to determine which option is best for your specific situation is to experiment with both CUDA and OptiX and compare their render times and performance for your particular scene.

You can also see the Blender documentation and community forums for more information on which option is best for your setup.

CUDA vs OptiX: What is the best Blender GPU? 

The best GPU for Blender depends on various factors such as budget, specific use cases, and personal preferences.

However, generally speaking, the NVIDIA GeForce RTX 4090 is currently considered the best GPU for Blender due to its high CUDA core count, large VRAM, and excellent performance in rendering tasks.

Also, other high-end GPUs such as the RTX 4080 and RTX 4070 Ti are great options for Blender rendering. They offer a good balance of price and performance.

Additionally, the AMD Radeon RX 6900 XT and RX 6800 XT are also powerful GPUs. These GPUs can deliver excellent performance in Blender rendering tasks.

Do I need CUDA for Blender? 

No, you do not need CUDA for Blender.

However, if you want to use GPU rendering in Blender, you will need a compatible graphics card with CUDA or OptiX cores.

CUDA is a parallel computing platform and application programming interface (API) developed by Nvidia. This allows software developers to use the power of Nvidia graphics cards for general-purpose computing tasks, including rendering.

OptiX is a newer, more advanced API also developed by Nvidia, which provides real-time ray tracing capabilities for more photorealistic rendering.

So, while CUDA is not strictly necessary for Blender, having a graphics card with CUDA or OptiX cores will significantly improve rendering performance in Blender.

Also, When it comes to rendering performance, a high-end CPU alone may not be enough to match the rendering speed of a powerful GPU.

GPUs are designed to perform many parallel calculations simultaneously, while CPUs are optimized for single-threaded performance.

This means that even a mid-range GPU with CUDA cores can outperform a high-end CPU for rendering tasks.

Are CUDA cores good for rendering? 

Yes, CUDA cores can be an excellent choice for rendering, particularly if you’re using a rendering engine that supports GPU acceleration.

CUDA cores are specifically designed for parallel computing and can significantly speed up the rendering process in Blender. However, the number of CUDA cores in a GPU is just one factor that affects rendering performance.

Many popular rendering engines support CUDA acceleration. For example, Cycles and OctaneRender can take advantage of the additional computing power provided by NVIDIA GPUs.

Using CUDA cores for rendering can lead to significant performance improvements and faster render times, particularly for complex scenes that require a lot of computing power.

However, it’s important to note that not all rendering engines support CUDA acceleration.

Also, the performance gains will depend on various factors such as the size of the scene, the complexity of the shaders and lighting, and the number and type of GPUs being used.

Which GPU is better for CUDA?

When it comes to selecting a GPU for CUDA-based workloads, such as rendering, the performance of the GPU will depend on a number of factors, including its CUDA core count, memory bandwidth, clock speed, and memory capacity.

Generally, GPUs with higher CUDA core counts, faster memory, and larger memory capacities will perform better for CUDA-based tasks.

NVIDIA is a leading manufacturer of GPUs that support CUDA, and they offer a range of products that can be suitable for different budgets and requirements. Some of their most popular GPUs for CUDA include:

• NVIDIA GeForce RTX 40 series: These GPUs feature the latest NVIDIA Ampere architecture and offer high CUDA core counts and fast memory. It also provides hardware support for features such as ray tracing and tensor cores. They can be an excellent choice for demanding workloads, such as rendering and machine learning.
• NVIDIA Quadro RTX series: Famous GPUs, designed specifically for professional applications, such as 3D modeling, animation, and visualization. They offer high CUDA core counts, fast memory, and advanced features such as ECC memory and NVLink connectivity.
• NVIDIA Titan series: These GPUs are a step above the consumer-grade GeForce series and offer high CUDA core counts and memory bandwidths. This makes them suitable for demanding workloads such as rendering, deep learning, and scientific computing.

Ultimately, the best GPU for your CUDA-based tasks will depend on your specific requirements and budget.

It’s recommended to review the specifications of different GPUs and compare their performance benchmarks to determine which one would be the best fit for your needs.

What does OptiX do in Blender?

OptiX is a GPU-based ray tracing engine developed by NVIDIA.

It is a real-time ray tracing solution that can provide high-quality and physically accurate images in real-time.

OptiX has been integrated into Blender as a rendering engine option, allowing users to take advantage of real-time ray tracing capabilities for faster rendering.

In Blender, OptiX allows for faster rendering times with the use of its AI-accelerated denoiser.

This denoiser uses deep learning to analyze and remove noise from images, resulting in cleaner and more realistic renders in a shorter amount of time.

It can also handle complex lighting and shading effects, such as caustics and reflections, with ease.

OptiX is especially useful for artists and designers who require real-time feedback on their work.

It can help them to quickly iterate and make adjustments to their scenes, without having to wait for long render times. Additionally, OptiX supports the use of GPU rendering, which can provide a significant performance boost when compared to traditional CPU rendering.

Importance of VRAM

Another factor to consider when choosing a GPU for rendering in Blender is the amount of VRAM (video RAM) it has.

VRAM is the memory on a GPU that stores the textures, geometry, and other data needed to render an image.

The VRAM or GPU Video Memory should not be confused with the system RAM that is attached to your workstation’s motherboard, although it functions in a similar way.

The more VRAM a GPU has, the more complex scenes it can handle without running out of memory.

Ultimately, the best GPU for Blender rendering depends on your specific needs and budget.

The amount of VRAM a GPU has affects its data storage capacity. This allows for more complex environment rendering.

When choosing a graphics card for professional work, memory bandwidth is another important metric to consider. This metric measures the speed at which data is transferred from the VRAM to the GPU.

A higher memory bandwidth will accelerate rendering tasks, resulting in time savings for the renderer.

In fact, the amount of VRAM in your graphics card can make the difference between rendering taking an hour to complete versus just ten minutes.

If you’re on a tight budget, a mid-range Nvidia GPU with CUDA support and at least 6GB of VRAM can offer good performance for most tasks.

If you have a larger budget and want the fastest possible performance, a high-end Nvidia GPU with the latest architecture and large amounts of VRAM may be a better choice.

Which renderer is best for Blender?

Blender comes with two built-in rendering engines: Cycles and Eevee. These engines allow you to render your scenes and create final images or animations directly within Blender.

Blender also supports render engines such as Radeon Prorender, Octane render, Corona render, LuxCoreRender, V-Ray etc.

However, these engines need to be installed separately before they can be used within Blender.

Again, the best renderer for your specific needs will depend on factors such as project requirements, hardware, and personal preference.

• Cycles: This is Blender’s default physically based rendering engine. This renderer provides high-quality output and supports a wide range of features such as ray tracing, global illumination, and volumetric rendering. Cycles can produce photorealistic renders, but it can also be slow for complex scenes.
• Eevee: This is a real-time rendering engine in Blender that uses modern GPU technology to provide fast rendering. Eevee is great for creating previews and visualizations in real-time, but it is not suitable for high-quality final renders.
• LuxCoreRender: This is a physically based rendering engine that supports unbiased rendering, bidirectional path tracing, and Metropolis light transport. This renderer provides high quality renders and support for advanced features such as motion blur, caustics, and subsurface scattering.
• Radeon ProRender: This is a physically based rendering engine developed by AMD. It supports CPU and GPU rendering and provides high-quality output, fast rendering times. Also, this renderer supports advanced features such as volumetric rendering and hair rendering.

When it comes to choosing a rendering engine in Blender, your decision may depend on your specific needs.

If you need photorealistic images and advanced features, Cycles is the way to go.

If you need real-time feedback and fast rendering times for interactive projects, Eevee is a better choice.

Also Read: How to Create 3D Cartoons and Animations with Blender 3D

Final Thoughts

In conclusion, CUDA and OptiX are both fast GPU rendering options in Blender. However, the choice between them depends on your specific GPU and project requirements.

When choosing a GPU for Blender rendering, consider factors such as CUDA cores, VRAM, and budget.

And when choosing a render engine in Blender, consider whether you need photorealistic images or real-time feedback for interactive projects.

Have you tried rendering with both CUDA and OptiX? What was your experience like?