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Cathy Foil

100% transparency on one face of a mesh increases display weight! WHY?

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While trying to cut down on lag I been going through my builds.  As many of you probably also do I use a combination of mesh, sculpties and regular prims depending on which is best suited.  So I decided to try and make my regular prims less demanding by going through and making all the faces that are hidden 100% transparent and a blank texture.

My thought is if it is 100% transparent then the graphics card won't have to work as hard seeing as it won't be rendering it thus making my regular prims less laggy.  To check this I clicked on "More info" on my build window.  To my shock the Display Weight actually went up not down.  I then rezzed a mesh, that I had several different textures, and made one of the faces 100% transparent.  To my shock the display weight went from around 300 to over 2200!

I could see if something was not 100% transparent like say 50% having a higher display weight because the graphics card would have to render the semitransparent texture and what is behind it.

So can anyone explain this?  Is it just a waste of time to make hidden faces of a regular prim invisible?

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The GPU renders what you tell it to, it doesn't care if it's fully transparent. It's not a waste of time tho because the next viewer update won't render fully transparent faces. ^.^

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Transparency is transparency.  It doesn't matter if it's 100% or 1%.  If its present at all, it requires an extra render pass to calculate.

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Chosen Few wrote:

If its present at all, it requires an extra render pass to calculate.

A special render pass that does some extra things is a better way of putting it. Extra pass implies that the viewer would only need one pass otherwise which is a few orders of magnitude off. The viewer has to do thousands of passes (draw calls) each frame to draw everything. You can see the exact number needed by turning on Develop->Show Info->Show Render Info, it will add an overlay in the bottom right that tells you all kinds of details, "Render Calls" is the one we're looking for in this case.

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Pamela Galli wrote:

Adding a partially transparent face increases the LI?  I have not seen that.

LI (Land Impact) is server side cost, and transparent textures won't increase it, Display Cost is viewer side cost where it shows up.

 

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LindaB Helendale wrote:

LI (Land Impact) is server side cost, and transparent textures won't increase it, Display Cost is viewer side cost where it shows up.

LI is determined by the combination of all the weights, or rather the highest weight. server cost is server side cost, so is physics weight. display weight is indeed viewer side. In other words, you can have something with little impact on the servers and still get a high LI.

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LI is dertermined by the highest of Download, Physics and Server weights. These all include server resource use, and download weight is also an estimate of part of the client (viewer) resource use.

Display weight is an estimate of  the amount of client rendering resource use. It includes a part proportional to the download weight, but also many other factors, such as transparency (4x multiplier), that do not affect the other weights. It does not contribute to Land Impact.

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Kwakkelde Kwak wrote:


LindaB Helendale wrote:

LI (Land Impact) is server side cost, and transparent textures won't increase it, Display Cost is viewer side cost where it shows up.

LI is determined by the combination of all the weights, or rather the highest weight. server cost is server side cost, so is physics weight. display weight is indeed viewer side. In other words, you can have something with little impact on the servers and still get a high LI.

Download weigth, server weigth and physics weights all measure server side load, download cost is the bandwidth needed in the server to send the stuff to view, physics weight is the physics simulation cost in the server and the server weight is the prim bookkeeping cost in the server.

 

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"Download" weight takes into account geometric complexity which does measure some part of the rendering effort. And currently we do render fully transparent objects, but we are changing that.

 

Charlar

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