How to reduce polycount on your SketchUp models
What are Polys?
Polys or polygons refer to a face that creates the mesh of an object, this can come in the form of triangles or quadrilaterals. These shapes are made from edges which are exactly what they say. Where these edges meet, these points are called vertices.
Why is this important?
The more edges and polys a model has the more effort is required to load, view, edit and generally look at the model which means that some machines can become very slow on start up or just slow in general as the computer has to put in so much work to just look at the model.
How to check poly/edge count?
Once you notice SketchUp is going slow, reducing your face count is a good start to try and help speed things back up, but first you’ll need to know what you’re working with.
- Head to Window > Model Info > Statistics and look at Edge and Face count
Models can be any amount of polys, and alongside textures and your machine specs, there is no set number to stick to or worry about. However I can say on a Mac with M1 chip, 6 Million polys is where I had noticeable frame rate loss. (I tested this by duplicating a mid-quality tree 16 times from the 3D warehouse)
Understanding the 3D warehouse
A number of these issues comes from people finding objects in the 3D warehouse. Which is great, it builds the community and allows other peoples work to be featured and appreciated. But there are some key numbers to take note of. Lets go through them
- The first is Polygon Count which we have already gone over. Organic structures will generally be much higher so have a look at multiple options before picking the first one you see. Take this tree for example, if I know I am going to be using it over and over then the 200 thousand polys will soon add up so I may go away and look for one in the 100 thousand range for those mid range shots and keep this for close ups or to use sparingly to create texture in the scene by adding variety.
- The next is file size, simply how big the object is and the storage it will take up. This does not directly correlate towards poor performance, a model of 500KB can cause more issues that one that is larger but worth keeping track of so not to enlarge your file. Especially if you plan to share or move the file around.
- Material count is the amount of materials used. This is more relevant for organisation or for rendering using plugins (Read below). Again more materials won't cause performance issues but having large or high quality textures will, most textures will be either 2K or 4K quality anything larger you may want to swap out sooner rather than later. If you plan to use the model as a background image/prop then having a 1k texture or even just a colour is plenty as that is not the focus and sometimes not even visible.
- The last to look at is Distance from Origin. This means how far away it will be from 0,0,0 in your scene (where the person spawns on a new file generation). While this won't cause performance issues, it can cause you to lose your models when you import them and if you don't find and remove them then you can start to notice performance issues as SketchUp is still thinking about that tree a few kilometres away and everything in between, for example.
When importing and testing different models from the warehouse after you delete the model the information and textures are actually left in the file, this can bloat the file size as well as cause a mess in the materials area. To sort this there is a Purge unused button in the model info area which removes that hidden information and any materials that are not currently assigned to a object. The fix button is also located here which can be used to allow SketchUp to look for any errors and attempts to automatically fix them.
Fixing the issues
If your model/scene is large, like a site plan for example, then hiding certain components will help. The usual cause of issues are trees and bushes, having them tagged can help quickly turn their visibility on and off or even group them based on the different sections you are working on.
Also changing the ‘Profiles’ of your edges in your style area will also help get some performance back. But to see more on speeding SketchUp up then see this article here which covers some of what was mentioned here but also has other tips
Turning off or hiding what’s causing your problem will help but to really fix this you need to look at your own work and the faces you are creating. As you draw, push/pull or generally add geometry to your file it's best to think how you might be able to reduce the amount of faces or even think if it’s going to be visible or not? Like cups in a cupboard, even if the cupboard is open will you be able to see past the first row of cups? If not, remove the rest.
How to avoid increasing that number?
As mentioned above trees and bushes are the main culprits of enlarging the polycount and other 3D warehouse objects are often not made with optimisation in mind. In the 3D warehouse there are two numbers. One is the size of the file and the other is the polycount. Both are worth looking at and keeping in mind, but also file size is caused by more than just the poly count so look at those numbers separately.
Proxies and Scattering
Some render engines have the capability to help you out, here we will talk about V-Ray as it has both of the tools someone might need to help reduce the work load on SketchUp. Note that these tools help SketchUp rather than help the rendering process.
A proxy means to be represented. In the rendering and SketchUp world this means that we can transform a model into a proxy. For SketchUp/V-Ray specifically, this comes in the form of a simplified model with no textures and only when looked through the eyes of the render engine does it then see the actual model with all its textures.
Scattering can take a library of models and then place that randomly over a set area with a set amount of instances (copies). This does achieve a similar result to proxies in terms of keeping your SketchUp space as empty or simple as possible to improve performance
Plug ins
While we are talking about plug-ins, let's talk about some options to help reduce the number of polys. Most plug ins will look at the mathematical way to reduce poly count so you can lose some of the artistic/organic value of a model when doing it this way but worth some investigating if you do plan to import models on a regular basis. Whenever bringing in objects from the 3D warehouse or from other 3rd party sites you never know how they were created or if they have been converted from another site/program, so it is always recommended to see if you can create your own version as if you have a low poly count or simplistic design in mind. That being said, not everyone has the time or experience to do this so let's look at some options.
Paid
V-Ray/Enscape - as these are both Chaos plug-ins, they have the same Proxy techniques mentioned above and can be useful for rendering and reducing poly count
SimLabs - This is an importer but worth noting it does have a strong polycount reducer when importing
Free
Universal Importer by Samuel Tallet on SketchUcation - While this is purely an importer it does have a low level polycount reducer when importing objects
CleanUp 3 by ThomThom - This can provide multiple options to clean up your model/scene in general not only reducing polycount
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