AccuRender nXt

advanced rendering for AutoCAD

This one introduces two new engines.  Both of these are very experimental at the moment. I may not retain either of them if they don't prove useful.  Although they appear very stable, there may be some hidden bugs.  Be careful using these for production until we have some confidence in their stability and characteristics.  The engines are only accessible via the nXtEngine AutoLisp command use (nXtEngine 2) -OR- (nXtEngine 3).

Both engines include more light pathways than the current product does and can therefore potentially provide more accurate solutions.  Two "tricks" which are used in the first two engines, transparent shadow rays and daylight portals, are not used in these new engines.  This gets rid of two big sources of inaccuracy.  Caustics pathways are automatically included.

Engine 2 can be much less noisy than the Path Tracer for most interiors.  It's convergence, on the other hand,  is not as graceful and will include some discrete artifacts.  It's usually a lot faster than the Path Tracer for interiors.

Engine 3 is a little more accurate than Engine 2, particularly when window coverings are involved.  It converges more gracefully, but slower for some interiors.  It is considerably faster on some exteriors.

Some things to keep in mind with these engines:

  • Light leaks in the corners are possible when doing interiors.  Make sure walls, floors and ceilings are modeled as slabs with thickness.
  • Both engines start slowly and accelerate.  Pixels/sec should increase as they proceed.
  • Using accurate IORs is very important.  IORs of 1.00 should not be used for glass.
  • Designating glass as Thick/Thin is more important with these engines.
  • Translucency is not implemented.  Allow Surface Roughness is.
  • These engines use more memory than the previous two.  64 bit is recommended.  Start your testing and low resolutions.

Let me know what you think-- I'm looking for feedback here.

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After loading nxt and trying to execute nxtengine2 or nxtengine3 this is what i get:

Unknown command "NXTENGINE3".  Press F1 for help.

I am using windows 7 64bit and autocad 2008



You have to follow the instructions exactly.  It's an autolisp command, parentheses and spaces are important.

A little emberassed... resolved. thank you!

Esta imagen la genere con motor 2, 9 horas 27 minuto 155 pases. Me gusto la textura de las paredes, el piso y la cantera en los muros, sin embargo creo qeu tiene demasiado birllo la ropa de cama y almohadas, tambien creo que le falta un poco a la textura de la madera. Creo qeu si es mas rapido el proceso y los resultados mejores en cuanto a la profundidad de los colores y contraste entre los elementos

Engine 3 is exhibiting some light leaks at the edges of the wall.  You'll want to model the floor and ceiling with thickness to avoid some of this (both should extend to the outside face of the wall.)

When using e3, and adding fog trough the advanced tab by checking the enable fog checkbox, there is no fog that appears on the render.

I haven't implemented fog or sub-surface scattering in the new engines.

And what about the combine path trace? Is it possible to combine nxtimages generated by the new engines?

Good question-- not in the same way, no-- but I'm working on this problem.

3 renderings. Path tracer and engine 3 1200 passes, engine2 about 600 passes (took forever). Only daylight is involved, hdri sky and sun. None of them is completely resolved. By comparing everything it strikes me that the transparancy of the curtains is more natural in the path tracer. Also the wooden floor has the most natural look and the subtle bump is visible when you look in detail. For the moment (correct me if i'm wrong) i'll stick with te path tracer for this kind of work.

Absolutely nothing wrong with sticking to the Path Tracer for the time being.  I am working on Engine 2 quite a bit-- about to put out a build by the end of today.  I'm getting the thing to converge a lot faster.  Each pass will probably be a little slower, but fewer will be required.  It would be great for me if you could repeat the Engine 2 test once I put it out.

Some notes--

Engine 3 which I'm not working on and may discontinue has a significant light leak along the top of the wall (ceiling modeled as a flat plane?)

Just comparing e2 and e1 (Path T)--

e2 is showing some very nice caustics paths which are not present in e1.  These are most readily apparent in the area by the end table.  Caustics due to the metal couch legs and end table are nicely accounted for. The central table is also exhibiting some caustics.

The back left corner of the room is also better illuminated using e2.  The reason is likely that the caustic path from the glossy floor is not properly accounted for in e1.

Hi Roy, I'm right finishing some tests and I will upload images in a couple of hours with some personal considerations.




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