Why Is Blender Not Able To Complete My Renders?

Like any software of its kind, Blender is prone to crashing depending on certain scenarios. One scenario where crashing is very common in blender is when attempting to render complex scenes and animations.

Blender may not be able to complete your renders if the render requires more video memory than what your GPU possesses. Blender can even shut down and close the project if you attempt to render an image that exceeds the limitations of your hardware.

The event of Blender crashing during the rendering process is perhaps one of the most frustrating events that can happen to any 3D artist that uses the software. Let’s go through some of the main things that can happen when Blender is not able to complete your render and how to fix them.

Blender Cannot Render An Image That Requires More Memory

If you attempt to render an image and then halfway through the rendering process, Blender effectively halts that rendering. The most likely reason for this is going to be memory. To be more specific, we’re talking about video memory, which is specifically attributed to graphics cards or GPUs.

This is not to be confused with system memory, which is referred to as RAM or random access memory. Instead, we are talking about VRAM with GPUs specifically.

VRAM is a type of random access memory that focuses on the display of your data as an image on your computer’s desktop. This is the key difference between VRAM and can traditional RAM. VRAM is focused on the display of image data in real-time. This is one of the key factors that makes graphics cards so useful for 3D modeling and playing video games.

In terms of 3D modeling with Blender, our scenes require a certain amount of video memory or VRAM. There are many factors in our scene that can attribute to the final output of memory required to render that scene.

If the required memory of your scene is greater than the total memory of your GPU’s VRAM. Then during the rendering process, you are likely to experience a failure of the rendered image. Blender would likely also display a command prompt indicating that you have run out of memory during the rendering process.

Regardless of how far along you are in the render, at the point of failure. Blender will not complete any aspect of that render. This can be slightly frustrating as sometimes Blender can go through several minutes of rendering before it fails.

The best way to keep on top of this is to view the memory requirements of your scene in the bottom corner of the Blender user interface. Make sure this value stays below the threshold of your current hardware.

A workaround to all of this is to use the Eevee render engine instead of cycles. Scenes created using the EV render engine are far less intensive on your CPU and your hardware in general as they focus on rasterized rendering instead of path tracing.

Another workaround is to use the CPU itself for rendering in cycles. The rendering process is likely to take much longer with your CPU than it is with your GPU. However, your CPU will not be bound by the limitations of your graphics card VRAM.

The way that your image is rendered is different on a background level between the CPU and GPU. So there may be some instances where the CPU is the only way to go. Especially if you want to maintain the use of the Cycles render engine for your projects.

However, a failure to render does not always amount to a crash, and something else can be the issue.

Objects Need To Be Made Viewable To The Render Engine

One of the most common issues that you will find when rendering your scenes is when your objects are invisible to the camera.

For example, you go to render a scene, and then the rendering process does complete, but at least one or more of your objects are missing from view, even though you’ve checked in your 3D viewport to see if your camera is looking at them.

In Blender, we have what are known as restriction toggles which can prevent you from either viewing or selecting your objects. In this scenario, it is likely that we have set up a certain object to not be visible when we render our image. Objects can be made invisible to the viewport, to the render, or both.

If we go to the outliner panel we will see that besides each of our objects, we have a couple of options. One of them looks like an eye icon. This indicates whether or not the object is visible in the 3D viewports.

If the eye is closed, then the object is invisible. This option, however, does not change whether or not that object can be rendered, and if you hide your objects in the viewport and then go to render the image, then that object will still be rendered as a part of the final scene.

The icon next to the eye looks like a camera and this will allow you to toggle the visibility of that object when rendering. If the camera icon is not highlighted and is instead greyed out, then that indicates the objects in question will not be rendered.

So left click on this icon to ensure that the object will be rendered the next time you click on that button.

Previewing Your Scene Through Your Camera

A good way to ensure that you have everything set up for your render is to preview your scene through your camera object. In order to render your scene in Blender, you will need at least one camera object to exist in your viewport.

The camera object defines many properties such as the direction and orientation of the camera shot, as well as other attributes like the depth of field and motion blur.

But what you see in the 3D viewport is not a direct representation of what you will see in the render, so you will want to look through the eyes of this camera object, not only as a means of previewing your scene, but also as a means of positioning your camera object into the correct location.

If you press the N key on your keyboard, you will open up the side panel. In the side panel, there are a series of tabs. Go to the view tab, and under the view lock option ticked the box labeled camera to view.

Next, press the Zero key on your number pad to transition into your camera’s view. You will notice that the center of the 3D viewport will be highlighted as normal inside of a border. And on the outside of that border, everything will be darkened. What you see within this box or border is the view of your camera object.

By the way, if you do not have a number pad, you can go into your camera view by going to the view menu in the header part of the 3D viewport. Then go to the viewport menu, highlight it, and from the sub-menu that pops up select camera. This will also take you into the camera’s view.

Because we have locked our camera to the view, if we attempt to orbit around our scene while viewing it through our camera, then the camera will move as well depending on how we navigate.

So if we orbit our view, the camera will orbit as well. We can pan the view to alter the camera positioning and we can even zoom to move our camera to and from a specific point of reference. This way we will be able to both preview our scene and adjust our camera positioning so that we can get our render just right.

Viewing A Blank Screen In Your Render

Sometimes you may find that you have a blank or empty screen in your render. And there are a few reasons why this can happen. The number one reason for render failure, as mentioned above, is the lack of a camera object in your scene. If you don’t have a camera object then Blender won’t understand exactly what it is you want to render.

In modern versions of Blender, it will not even attempt to render if you don’t have a camera and will just tell you that you don’t have a camera in the viewport.

If your render appears black, then this could mean that your exposure levels for your scene are set to 0. Every scene has a default level of lighting, even in terms of its environment. While lighting objects are used to define the character of a scene, they are not strictly required to provide base lighting as this can be done with the environment itself, although not recommended.

However, if the exposure level of our environment is set to zero, or if the light strength of our environment map is also set to zero, then the scene will appear blank. If there is no other lighting present in our viewport.

A far less likely reason when using the Cycles X render engine is that the surface option has been filtered out. The surface option is one of the hidden options in Blender that can be toggled on and off to display viewports geometry. 99% of the time you’re not even going to know where this is, let alone accidentally press it. But it is still a way to result in a blank screen, so we’re going to cover it here.

Go to the View Layers tab in the properties panel and then go down to the filter section. In this section you will find an option for surfaces. If this box is not ticked, then that means that Blender will not render any geometry for your scene. Make sure that this option is ticked so that it doesn’t prevent Blender from rendering geometry.

One last troubleshooting method is to focus on the clipping value for your camera. Like the 3D viewport itself, your camera has a clipping value that will not render anything outside of that range.

For example, you could have a minimum clip value of 0.1 meters and a maximum value of 100 meters. With these clipping values in place, any object below 0.1 meters in size will not be rendered. Likewise, any objects above 100 meters will not be rendered either.

You can change the clipping values in the 3D viewport by going to the view tab in the side panel. However, while this would fix issues in the 3D viewport, it is not the same setting As for the camera object.

If you want to change the clipping values for your camera, then select the camera object, then go to the object data properties tab in the properties panel. It will look like a green camera icon from the column of tabs.

Under the lens section in this tab, you will find the clip starts and clip ends. The clip start is the minimum value and the clip end is the maximum value. Adjust these to whatever values you require to view your larger or smaller objects.

How To Render A More Complex Scene Easily

If Blender is struggling to complete the rendering process because the scene is just too intensive, then there are a few methods that you can try to make complex scenes easier.

The quickest method is to reduce the base resolution of your render. This can be done in the output tab of the Properties panel. It’s the first option you will see, so you will be able to change the resolution either as a hard value or as a percentage of the base value.

You could also change your render engine from cycles to Eevee. This engine is a lot simpler in terms of how it renders in terms of geometry, materials, and especially lighting. It’s therefore going to be a lot less intensive on your hardware and much easier to render as well as it being much faster.

The only downside to switching to Eevee is that it will have a profound impact on the appearance of your scene. Eevee is built for speed, while Cycles is built for realism. So the more realistic you try to make your scene, the more it will be impacted when you switch over to Eevee.

Another method is to reduce the total amount of geometry in your scene. Geometry density plays less of a role these days in modeling and in game design as it’s no longer as impactful on the performance of most machines.

Despite that, though, there are some limitations, especially if you’re using slightly older hardware. A good idea is to assess all of the objects in your scene and judge whether or not the amount of geometry is necessary for the detail that is provided for each object.

If an object is too dense in terms of its geometry, then you can use specific tools to reduce that geometry density without dramatically reducing the detail.

A quick and dirty method is to use the decimate modifier, which you can use to have full control over how much geometry you want that object to have. Keep in mind that this method can destroy the topology of the model, which will affect things like animations.

A slightly more complex method of making complex scenes easier to render is to bake some of the properties of that scene. Baking is a process where you take an attribute of a scene and you in a way bake it ahead of time or render it ahead of time, at the cost of it becoming a permanent fixture in the scene.

One example of baking is to bake shadows onto your objects. You can position your lighting and then bake the shadows of objects onto other models. This then reduces the need to re-render that property in the final render. You can also do this with other attributes, such as the finer details of your geometry by baking normals. As well as being able to bake texture maps onto your models.

Not Having A Camera In Your Scene

To successfully render a scene you will require at least three objects. The first will be at least one mesh object that is the actual geometry that you will view in your render.

The second object will be the lighting which will be used so that you can actually see what is in your scene and not just a black canvas.

And then finally, you will require a camera object which is going to act as the eyes for your scene. Without your lighting, your camera, or your mesh object, you will just end up with a blank render or a prompt saying that you are unable to render at all, which is the case when we do not use the camera object.

Make sure that you have at least one camera object at all times in your 3D viewport and then Blender will always default to that camera as the view for your render.

No Active Lighting In The Viewport

While the environment itself can have a degree of lighting to it, this will be a very flat type of lighting, unless it comes in the form of a HDRi image.

It is important to have at least one type of light object to provide a direct light source to your models. Ideally, though, you should have more than one in certain scenes to create shadows that follow different directions.

Blender has an add-on that would allow you to create a three point light setup so that you can better view the objects in your scenes. Indoor environments in particular can sometimes have multiple light sources, such as the roof light as well as monitors like televisions and desktops as well as mobile phones.

Thanks For Reading The Article

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