A long time ago N3V posted 200 poly equivalents overhead per texture, 300 per mesh and it referenced GMAX with lots of small textures. It's probably based on that.
Cheerio John
That rang a bell John, and I've investigated it a little further.
I downloaded 18 recent single-mesh Sketchup assets and analysed them for poly count and textures, compared to what the RubyTMIX descriptions say.
"System load from geometry" is simply the triangle count, as verified by PEV Mesh Viewer.
"System load from textures" is calculated from the number of textures. Since it's added directly to the actual triangle count to give a total system load, it's units must also be triangles (or "triangle equivalents"). I would still love to know how that equivalency between textures and triangles was derived and whether it's even approximately valid.
Here is the linear equation that RubyTMIX is apparently using to calculate texture load;
System load from textures = (Number of textures x 300) - 300
So it looks like the important factor is 300, not 200, but it’s basis is obscure.
The large white data point on the graph is not a measurement, but an extrapolation of the line to the X-axis. It means that, according to RubyTMIX, an asset with 1 texture has no "system load" from the texture (!). In reality, that cannot be right because 1 texture is at least 1 draw call. It would be more realistic if the line started at the 0,0 point, meaning no texture = no texture load. In other words, RubyTMIX's calculation systematically
under-estimates the contribution of textures to the total load.
Also note that this linear relationship takes no account of how large or complex a texture material is (i.e. image sizes or number of maps involved, such as diffuse map, normal map etc). So it is definitely a very over-simplified measure.
Rearranging the equation gives this;
Number of textures = (System load from textures/300) + 1
For people downloading RubyTMIX assets from the DLS, you can read the texture load details from the asset description and calculate the number of textures involved before you decide to download. Anything over “300” for texture load means there are more than 2 textures. And remember that each texture is
at least 1 draw call.
.