Fractal Trees vs Images for trees

[Albert D Hart]

"I'm usually rendering fairly detailed AutoCAD architectural models on 3D
modeled sites with lots of AccuRender trees and shrubs.  I was wondering
what AccuRender 4 (using Acad2004) and AccuRender nXt (using Acad2011)
actually "sees" when you select a view to render.  Do they "see" and have to
"consider" the 50 trees behind the building (adding a lot of calculating
time to a rendering), or do these programs "hide" and never consider the
stuff that's hidden in a view by other entities?"

Everything in the models takes time to render, so we recommend you use images for background trees, and only use fractal trees for tree for which the additional detail will make a difference.

The 3D Fractal Plants show more and more detail, the more you zoom in on them.

But for plants which are in the background, the 2D images work well and save considerable rendering time.

Here is a rendering of two plants - zoomed in - the one on the left is rendered as a 2D image, the one on the right is rendered as a 3D, Fractal plant. If you look closely you can see the better detail in the 3D, Fractal plant.

However, when these two plants a zoomed out a bit the difference is almost not noticeable.

[Steve Wojtynek]

Sounds like good method... something I need to look into as I've never used tree images.

Assuming I want to continue working the old way using only fractal trees... Does AutoCAD and AccuRender take time to calculate trees hidden by buildings etc?  I can see from the on-screen messages that go by, that the first step AccuRender does is to change all the AutoCAD render-able objects to faces.  I assume it converts all the objects in the model (including the hidden stuff).  Does it then use the "front row" of faces to hide the "back row" of faces?  If that's the case, I can see that turning off the trees that are hidden would save a lot of time.  (But then again... I charge by the hour!  Just kidding... I don't like wasting time.)

[Roy Hirshkowitz]

nXt doesn't really work like that-- all of the objects need to be taken.  An object which is hidden from view may show up in a reflection, a shadow, refracted through glass, contribute to diffuse reflection of light in the scene, etc..  

OTOH turning off objects which don't participate does not usually save a lot of time unless you are in a low-memory situation.