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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I attach the lighting file.. don't know if it's useful. You make me to put attention to points I didn't notice before: the countour of the opening in the ceiling above the piano is washed by some light, but light itself doesn't enter by the entrance. The glossiness of the black painting (the chalkboard) is not present in none of the engines. The flowers of the orchid are too dark in e3, but I suppose that this is due to the contast with the too luminous exterior. Yeah, the bulb light of the Arco lamp is definitely much better in e2 and e3.


Here it is (with the version I'll upload soon) at 300k pixels for 15 minutes daylighting only-- I reset everything I could find to default.  Almost artifact free.  I'm running a 15 minute Path Tracing now for comparison.

Excelent! There's a strange light diagonal reflection between the two plants close to the sax. But it might be due to the cristal table.

Here they are side by side.  Path tracer has a much longer way to go.  The diagonal stripe you noticed is absolutely a caustic-- with contributions coming from the floor and the table.  As predicted, it's absent in e1.

Still have to perfectly understand what a caustic is, but nice btw!

Un caustico es el reflejo o paso de luz atravez de un objeto transparente

10 minutes with 2 lights.  Jorge is correct-- the caustic in the case above is the bounce from the shiny (glossy) portion of the floor.

On E2: There are no reflections on the armchair and the piano chair, the color of the wall under the picture is strange, the light above the picture (and the fluo neonlight?) seems to be not enough strong. I prefer the general colors of the E1(sky saturation?), and the spots on the ceilling are less aesthetic than some regular specks. In real photo, we could find these grainy effect, but never these spots. But the E2 looks so fast... So promising! E2 seems to have almost finished its work.

There's clearly a bit of a problem with slightly glossy materials like the chairs-- the same problem showed up in Jan's scene where a slightly glossy floor was missing some reflection.  Not sure what's up yet.  The "strange" lighting by the piano and the picture on the right are artifacts which will resolve, as are the "spots" on the ceiling.  This engine will produce larger spots than the path tracer.

 " and the spots on the ceilling are less aesthetic than some regular specks."

and the grainy speckles which are most irritating on plain surfaces can be removed somehow with the despeckle filter in PS

Hi Roy any chance for the next development to have a option of more sharper underside lighting for external. cos to dissolve the noise really need extensive time . the default external rendering dun light the underside with diffused liglighting from the sun.





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