Use a finer mesh. The raytracer can do only mesh level displacements, not micropolygons.

The raytracer can do only mesh level displacements, not micropolygons. I see. Is this a bug or a feature?

It's by design. A REYES renderer breaks up your scene into millions of micropolygons, which is how it can do these fine displacements. Since all these micropolygons would not all fit in the computer's memory at the same time, only those micropolygons that are necessary for the patch that is being currently rendered are being created and deleted once they have been rendered. A raytracer instead needs access to the whole scene, as it doesn't know in advance what objects the reflected ray will intersect. To save memory, the raytracer gets to see only the base mesh, not the micropolygons. FireFly is a hybrid renderer, so it incorporates both a raytracer and a REYES engine. REYES is being used for the main rendering, and effects like reflection, refraction or ambient occlusion are being handled by the raytracer.

stewer Poser5 render the micropolygons as well in the reflection and this feature in Poser6 is a BUG, I try to use many displacement maps and not one relfect the displacement map correct in poser6 as it have to be... Cath

Really? I have to try that out.

salt (bookmarking)

I've used real skin shader with displacement in P6 and have had problems with the reflections.

I have never been able to get displacement to render in P5 or P6.

"I don't have P5 here on my computer anymore and I found this one, I made series of the images with the same fur effect that reflect in the reflection, and used displacement maps..."

That image seems to confirm the same thing Stewer was saying, Cath. The "displacement" you see in the reflection looks more like a bump map, while the object itself is obviously real displacement. If you look closely at the edges of the object in the reflection, you'll see that they're still very smooth, while the displaced object above it has "furry", roughly displaced edges. It seems all P5 did there was turn your displacement map into a bump map in the reflection. It looks close, but not the same. :-) It's definitely not representing the displacement on the micro-polygon level in the reflection. Message edited on: 08/10/2005 19:25

My understanding is that it is a known issue that was done to reduce raytracing render times. I don't want to speak for them but I have mentioned it to E-frontier and they already knew about it.

"My understanding is that it is a known issue that was done to reduce raytracing render times. I don't want to speak for them but I have mentioned it to E-frontier and they already knew about it." You mean it was deliberate "feature" they decided on? Hmmmm. Sounds like a lame excuse from E-frontier to me. ;-P If someone is using raytraced reflections with displacement, it seems logical that they would want the displacement reflected, regardless of rendertime impact. Otherwise, why bother using a reflective surface in the first place? Sounds more to me like a problem that they just haven't figured out yet. ;-) If it IS even technically possible to get micropolygon displacement visible in raytraced reflections, then why not the option of allowing us to turn it on or off? Maybe in a future update. ;-) Stewer, does micro-poly displacement show up in reflections with other hybrid REYES renderers? I don't know the answer, just curious if you do.

I just know they know about it and it sounded like a render time concern atm. Don't get too outraged or anything. I don't want to get in trouble. Look at it like this. It might be easy to change in the future. :)

"Don't get too outraged or anything. I don't want to get in trouble." LOL. No worries, Anton. It takes a lot more than displacement and reflections to get me outraged. ;-P

NaCl (Bookmark)

Stewer, does micro-poly displacement show up in reflections with other hybrid REYES renderers?

Well, some of them simply create a finer mesh and send that to the raytracer, the way non-micropolygon renderers like C4D do it, in which case you get all the disadvantages of that method (memory consumption, non-view dependent tessellation). SideFX' Mantra or Pixie require the user to define the tessellation level. Pixie's documentation notes that "True displacements for raytracing may be very expensive. "

The documentation of 3Delight 4.5 says the following:
"By default, 3Delight renders ray traced displaced geometry using bump mapping, meaning that only surface normals are affected by displacement shaders, not geometry.

OK, default is the same as FireFly's. Let's read on:

*it is important to note that there is an additional cost when using true geometric displacements in the context of ray tracing, for the following reasons:

3Delight needs more memory to hold displaced geometry (even though it uses a caching mechanism to reduce memory allocations).

Displacement bounds expand primitives' bounding boxes, this has a bad effect on ray tracer's space partitioner, meaning less efficient ray / primitive intersections. It is clear that badly set displacement bounds (or extreme displacement) can make ray tracing of true displacements very costly.

For many primitives, geometrical intersections are less efficient than the analytical algorithm 3Delight uses for non-displaced ray tracing."*

No information is given about the tessellation level or how to control it. And I can't experiment with it because 3Delight claims my license is expired and a new one refuses cooperation.

Pixar's PRMan - I have never used it and don't have it's manual, but judging by the papers the published, Pixar has put a lot of research work into raytracing large scenes, on-the-fly tessellation, multiresolution caching etc. Sounds like they have figured something out, and will probably sue your butt off if you implement the same ;)

BTW, Renderers like 3ds or C4d are not doing micropolygon displacement. For example, see this discussion:
http://forums.cgsociety.org/showthread.php?t=189573

Aha! That explains some of the effect I saw in P5 while rendering reflections of displacement maps. With improperly adjusted min displacement bounds, I would get vertex clipping artifacts in the direct view, but reflections appeared to show the displacement properly. I now realise I was seeing a bump map representation of the displacement in the reflections. Shining by reflected light ;-) Thanks for the detailed explanation Stefan :-)

Well, at least it's good to know. If you want to make a complex scene that relies on displacement reflection, it's good to know before you do it...