Second Life Render Metadata

You may have noticed the item in the Develop menu labeled Render Metadata. At this week’s Content and Mesh Creation user group meeting Zed Tremont asked about getting more information for items in this menu. Nyx Linden provided some insight into these items.

Second Life Viewer’s Render Metadata Menu

If you have not noticed the item look in the top menu try: Develop (Ctrl-Alt-Q – Advanced has to enabled in some viewers to see it Ctrl-Alt-D)-> Render Metadata.

These tools are more for developers than ‘for creators.’ But, creators can use some of them. Unfortunately most of the items are not explained in the Second Life™ Wiki. Nyx says, “…at the moment our documentation around this *is* the source code, most of these displays are mostly used by our graphics engineers, they’re not intended to be general-use displays (hence the lack of documentation).”

Bounding Boxes – To provide the illusion of solid objects in a purely mathematical world a physics engine (another piece of software) is used to calculate when things collide. That keeps our avatar from walking through walls. You can activate this item to show bounding boxes in the viewer.

Bounding Boxes Display

One can use bounding boxes with mesh objects to see how physics and collisions will be handled. You may also be able to see when an object is overly complex and find ways to simplify it.

 

Color Legend for Bounding Boxes

The next problem is understanding what all the colors mean. Viktoria Dovgal has figured that out: Bounding Box Colors. Her’s was the only key I could find and Darien Caldwell tipped me off to that page.

Normals – Normals are known by 3D modelers. They are a line drawn from a surface/polygon to show which direction is the ‘front’ of the surface. In Second Life only the front or outward facing surface is rendered. When working with mesh the faces may be oriented the wrong way and seemingly disappear. This display can show a creator what the problem is.

Displaying Normals

If one is using Blender there is a setting to show normals in the display. In the right side panel of the 3D View in the Mesh Display (you must be in Mesh Edit mode) section is the control to turn on Display Normals.

Octree – Nyx describes the octree as: “… shows how the world is divided up into different ‘zones’ for purposes of updating, etc. You see colors change as various items need to get updated – the higher the frequency of updates, the more load. You can see a bunch of updates happen as you zoom in and out.”

Octree Display

I am assuming that red stuff is showing the items placing the most load on the viewer.

Shadow Frustra – Nyx says, “I presume faces are showing up shortly while updating ambient occlusion or “shadows”. This deals with our shadow rendering, its more for developers, less helpful for creators.”

Shadow Frustra Display

Physics Shape –  Nyx says, “Interesting to see where to reduce physics shapes on a sim, though [color] legend is missing. Physics shapes are more helpful, as it shows you what shapes the server uses for detecting collisions. This is particularly important for imported meshes and Pathfinding characters. This is probably the most useful one for creators trying to optimize their content.

Drongle McMahon describes the item as, “I don’t know the actual numbers, but the color indicates the magnitude of the physics weight, that is the strain it puts on the physics engine. Blue is nice and simple, going from green to yellow to orange to red as the weight becomes excessive.

It shows you that the default convex hull is smaller than it should be!

Physics Shape Display

In February this feature had some bugs and failed to show some convex hulls correctly. I don’t know if that has been fixed. So, few people use these items fixes are low priorities. But, this is an excellent tool for testing mesh objects to see how they are seen by the physics engine.

If you have not read Physics Optimization, consider reading it. That information and this display should help you reduce the prim count/land impact cost on your land.

Occlusion – While I know what occlusion is about, I’m not at all sure there is any use for the item or exactly what it is displaying.

Occlusion Display

Render Batches – Nyx said, “[Render Batches] are groups of content that can be drawn together in one pass. Every time you change the properties of an object (textures active, shiny, etc). then the whole pipeline needs to stop in reset, so batching things is good.

Render Batches Display

Here are a number of items I don’t know about and haven’t found any information about. These are for internal use by the Lindens developing the render engine.

  • Update Type
  • Texture Animation
  • Texture Priority
  • Texture Area
  • Face Area
  • LoD Data
  • Build  Queue

Lights – This shows lights in the visible scene. I suppose it could help builders light their scene.

Display Lights

Collision Skeleton – Nyx: …which shows you the bones that your camera can focus on for picking.

RayCast – This is an interesting display. For those of us making clothes and wanting to know what the SL Avatar skeleton looks like in world, this display shows it. I suppose for combat gamers this is the closest display there is to show the collision shape of the avatar.

RayCast Display – Interesting

Where you place your cursor greatly affects this display.

Wind Vectors – I wrote about this one some time ago in: #SL News 2 Week 41. Check out that article if you are interested in this display.

Render Complexity – Nyx: …which uses the display weight algorithm to give a “score” to each avatar in the view as to how complex they are to draw. There actually is documentation on this one! Keeping these numbers low will help with your performance.

Advanced Build Panel – Complexity

The only thing is this feature has been broken for a long time. The equations for the process were finalized in October 2011, just a hair over a year ago.

There is a wiki page Nyx made describing the math: Second Life Render Complexity.

We also see the Render Complexity displayed in the Build Panel’s Advanced panel. The Weights section’s Display is the Render complexity of the selected item.

Use the “Display Weight” metric in the build tools while working on attachments to help here.

Attachment Bytes – shows how much data is needed to store each avatar’s attachments. The value of this is an indicator of how much trouble and time will be needed to get you from one region to another.

Sculpty Texture Display

Sculpt – shows the size of the sculpt maps used in sculptie objects. Using this display creates lots of jammed together numbers. You can use it to see how complex a hair-do is or any sculpted object.

Texture Density – There are 4 settings for this item. I am not at all sure what it does.

Summary

Some of these will drag down your frame rate. Others will take a couple of minutes to update.

Hopefully this information gives you a few more tools for gaining insight to your building in SL.

3 thoughts on “Second Life Render Metadata

  1. The one for lights is also really handy for finding unusual stray light sources. For example, you might pick up a chair from somewhere that emits light for some bizarre reason, and place it in your home during the day. Then some time later during the virtual night, you notice that you have light where you shouldn’t. A chair isn’t a usual suspect for being a light source so you might easily overlook it. Turning on the light metadata is a good way to find and identify objects like this.

  2. Occlusion Display helps to see how objects are visible or now when you use Object Oclusion. You can see in this mode, how some objects disapear while you look at them through others. For example, using a big prim as wall, look at what is behind and then move your camera slowly till the big prim hides all objects that was behind this one. Every object have an area like the bounding box, when certain percentage of that box is covered (hidden) by another object, that object disapears making the render engine to get better performance. It also works on things when you arent facing them. Depending of the size, placement, distance and nature of the object, this can or not disapear.

    I did a small video long ago showing a friend what all that means and how good is to raise the viewer performance.

    http://www.youtube.com/watch?v=wg7NnlT8d9s

    Regards.-

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