Why is the prim count so high?

David Starling · November 27

Total beginner here with Blender.

Why is it so high? Even though I scaled it down and it's tiny?

It's a basic spring, how on earth is that so high with land impact?

ChinRey · November 28

58 minutes ago, David Starling said:

Why is it so high? Even though I scaled it down and it's tiny?

It's the Lowest LOD model. If you can get it down to 12 tris or less you should be fine.

I don't normally recommend this cheat but if I understand you right it shouldn't do any harm in this case: In the Level of Details tab, change Lowest to "Generate reliable" and the limit for it to 0.

Edit:

Looking closer at the image, you have another unrelated problem: It's not possible to have an object with a size smaller than 1 cm in SL so you have to find a way to work around that too. The simplest way would be to add a larger horizontal triangle with its own material and apply a fully texture to it. Try to make it as big as 10x10 cm or so. That would also compensate a bit for the LOD butchery I suggested as a solution for the LI issue.

To explain a bit more, download weight is first calculated separateky for each LOD models and then the four values are weighed towards each other depending on how often each is estimated to be displayed (which again depends on the size of the object). For an object as small as this, the low, mid and high models will only be used when you cam in very closely onto it, so it's really only the lowest LOD model that counts. Unfortunately it also means that the lowest model is the one you actually see in-world and you can't really make a credible spring without adding quite a few tris, far more than you want for the lowest LOD models. A spiral is one of the most awkward object shapes you can make for SL.

You can compensate to some degree by artificially increasing the object's nominal size. Getting this absolutely right is a very fine balance but even the crude increase you need to get it over the 1 cm limit should help a bit. If you are willing and able to put in some time, you can experiment with different sizes for the transparent triangle. Ideally you want it to be just big enough to get the download weight to 0.5 but anything up to ... say 2.0 should be acceptable.

Another solution is to use an impostor for the LOD models but I'm not sure if that really is a beginner's technique.

Edited November 28 by ChinRey

Aquila Kytori · November 28

As @ChinRey has already mentioned you need to work on reducing the complexity of the Lowest LOD model.

What are LOD models ?

to save time I asked Chatgpt :

" LOD (Level of Detail) models are different versions of the same object in a game, with each version having a different level of detail. The idea behind LOD is to use simpler models when you're far away from an object and more detailed models when you're close to it. This helps the game run faster and look better without using too much computer power.

Here's how it works:

High-LOD model: This is the most detailed version of an object, with lots of polygons (the little flat shapes that make up 3D objects). It looks great when you’re close to it because you can see all the fine details.
Low-LOD model: This is a simpler version of the object, with fewer polygons. It looks less detailed, but it’s good enough when you’re far away from the object, and it helps the game run faster.

Why are LOD models used?

Games are full of objects, and rendering (drawing) every object in high detail all the time can slow down the game, especially if there are lots of objects on screen. So, LOD models are used to make sure that objects closer to the player are detailed, while objects farther away are simpler, saving processing power and helping the game run smoothly.

In short, LOD models are like different "versions" of a game object that change depending on how close you are to them!"

Second life mesh uses 4 different LOD models.

example of naming the LOD models in Blender

High LOD model, Spring
Medium LOD model Spring_LOD2
Low LOD model Spring_LOD1
Lowest LOD model Spring_LOD0

The added suffixes _LOD2, LOD_1 etc are important. The SL mesh uploader will look for these and if found in the same fold as the high LOD model will upload the lower LOD models automatically for you.

To create each of the lower LOD models we can make a copy of the High LOD model then use Blenders Decimate modifer set to Un-Subdivide on each copy.

The Lowest LOD version of the spring will be just a simple cylinder of 12 triangles.

The Un-subdevide option of the Decimate modifier works best if we start our spring with a number of vertices = to the power of 2 for example 8 , 16 or 32.

We will use 16 vertices per edge ring.

This is the High LOD Spring model: As @ChinRey mentioned Bounding Box dimensions are going to be important. The smallest an object can be in SL along X, Y or Z axis of its BB is 10mm. The spring is smaller than that along X and Y. We will fix that later on but for now just note that we can view the BB of an object in Blender by checking the Bounds > Box option in the Object data panel > Viewport Display.

Now we have our High LOD Spring object and given it a name in the Outliner we can make a copy of it for each lower LoDs.

Select the Spring object > Shift + D to make a copy then move it along the Y axis 0.03m. G Y 0.03. This will be the Medium LOD model. Give it the name Spring_LOD2 in the outliner.
Repeat for the other 2 lower LoD models. Spring_LOD1 and Spring_LOD0

Now we start reducing the complexity / triangle count of each of the lower LoD models.

In Object mode select Spring_LOD2 object.
Add a Decimate modifier to it.
Set it to use the UN-subdivide method.
Set Iterations to 1. This will reduce the number of triangles for Spring_LOD2 by 50%.
Apply the Modifier.

Repeat for the Spring_LOD1 object but this time set the number of iterations to 2. This will reduce the number of triangles to 25% of the original model.

As mentioned above we are going to replace the lowest LoD model by a simple 6 sided cylinder.

Because we moved the copies of the Spring object in Object mode the origin should still be at the base of the model.

In Object mode select the Spring_LOD0
Move the 3D cursor to the same position as the object origin with Ctrl + S > Cursor to selected.
Add a mesh circle at the position of the 3D cursor ...... Shift + A > Mesh > Circle. In the Last operator panel that pops up bottom left hand corner of the viewport set the number of vertices for the circle to 6 and the radius to 0.003m.

Next in Edit mode we extrude the circle up along the Z axis until its top edge is aligned to the top vertices of the Spring.

Edit mode , select circle, E to extrude followed by G Z and drag extrude edge ring upwards. Eyeballing it is close enough.

Back in Object mode select the circle object ( now its a cylinder) and to remove the hard vertical edges we shade it smooth. Object menu > Shade Smooth.
We can now select the Spring_LOD0 and delete it.
Rename the circle object Spring_LOD0

Our lower Lod models are almost complete now :

All that is left to do is to extend the Bound Box so that it is greater than the 10mm along each axis. we are going to do this by first adding a plane at the base of the Spring object.

Select the Spring object.
Ctrl + A > Cursor to selected.
Shift + A > Mesh > Plane to add a plane at the position of the 3D curosr.
In the last Operator pop-up panel set the Planes Size to 0.02m

If we now join the Plane object to the Spring object this will increase the Bounding Box dimensions to be 0.02 x 0.02 x 0.02m.

In Object mode, first select the plane then Shift select the Spring object.
Ctrl + J will join the 2 objects to be a single object.

We could leave it as is with the plane at the base of the Spring, give the Plane its own material then when rezzed inworld set the plane to be 100% transparent. But I prefer an alternative method of dealing with the unsightly plane. We can reduce the plane first to a triangle then we can collapse the triangle so that it as zero area and looks like it is a single edge. when rezzed inworld this triangle will be invisible. so lets try that.

In Edit mode, select one of 4 vertices of the plane then Shift select a second vertex on the same edge.
With both these vertices selected hit the M key to open the Merge menu and choose the At Last option. We are left with a single triangle at the base.
Next we collapse the triangle by selecting one of the triangles vertices and sliding it along the edge until it stops at a second vertex. Select a vertex hit G twice. Then drag the vertex along an edge until it stops when it meets a second vertex. (Using the G G command confines the movement of the vertex to one of the 2 edges of the triangle). The result should look like we have a edge across the bottom of the spring where before the plane was. In reality this is stil a triangle consisting odf 3 vertices but no area.

IncreaseBB.gif.9ba5150a95700f07bb5aef3390f8b2e7.gif

Repeat for the other 3 Lower LoD models.

To do that in edit mode you could select the collapsed triangle make a copy of it using Shift + D the separate it using the P key. Then in Object mode with the copy of the collapsed triangle selected move it to the base of the next Spring object using G Y 0.03. then joining it to that lower Lod model using Ctrl J as we did before. But I think it may be easier for you to simply add plane at the base of each of the lower LoD models and repeat the joining and collapsing method.

Now we are ready to export our models out of blender. Select the Spring object > File > Export > Collada (.dae) and in the Collada export window select the sl+open sim preset then give the model the name Spring and then export. Repeat for each of the other 3 objects. Giving each the correct suffix. _LOD2 LOD_1 and LOD_0.

Upload to SL using the SL uploader. Build > Mesh Model.... select the Spring.dae file and the uploader will automatically upload the lower LoD models for you.