Ray trace objects On/Off

Started by AndyWelder, October 01, 2011, 06:56:38 AM

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AndyWelder

Thank you for the link, Kadri, very interesting; I wouldn't have found this in the huge pile of search results on "micro render".

What's interesting and very promising is this reply from Matt: Would it help you if there was the option to specify the rendering method on a per object basis?
My answer to this question would be "YES!" because this would solve the problem I ran into.
"Ik rotzooi maar wat aan" Karel Appel

dandelO

#16
Then I'm not sure I understand your problem at all, Andy. You say the needles on Walli's trees don't use image mapping, and they are each six sided polygons per needle, is that what you're saying? Surely the trees would soon become pretty unmanageable if every single needle on every single twig were an object in itself!

I really can't see that being the case, I can even see repeating needles in the hi-res renders the NWDA guys posted to show off these trees, although, I'm often very wrong. I don't believe that these trees use no image maps for the needles and that you are, indeed, seeing the mesh in your 3D preview before needle alpha has been taken into account.

Kadri


Andy i tried one object and there was the same problem.

I tried some very near and far renders to better see what the problem could be.
Not sure but it is as if the two renderer's do some kind of different detail rendering-or level of detail.
Looks like Martin is right, because the problem gets more apparent as you get farther from the object.

dandelO

#18
I asked about this in 2009, here's my version of the question(the part in bold type regarding difference between RTO and MP rendered grass clump objects) and Matt's reply...

Quote from: dandelO on December 16, 2009, 01:10:40 PM
I'm still noticing a real difference in render time with objects in scenes, specifically internal grass clumps, since they were mentioned before. Using the micropolygon renderer is nearly twice as fast as the new ray traced objects option. Even with low AA settings. This seems to be contrary to the release notes.

Micropolygonal rendering seems to also look better, aswell. Ray tracing grassclumps seems to me like using very low quality settings in the old MP renderer. They are barely visible when raytraced. I'm confused.

I'll wait on more documentation on these settings, like Matt said was coming soon.

EDIT: Thanks for the clarification on which objects are ray traced, Matt. We posted at about the same time so I'd missed your last post.

P.S. I'm not complaining, not by any means, just confused. Thanks for the input and help. :-[
Quote from: Matt on December 16, 2009, 03:12:04 PM
Quote from: dandelO on December 16, 2009, 01:10:40 PM
I'm still noticing a real difference in render time with objects in scenes, specifically internal grass clumps, since they were mentioned before. Using the micropolygon renderer is nearly twice as fast as the new ray traced objects option. Even with low AA settings. This seems to be contrary to the release notes.

With simple objects or very few objects, ray tracing the objects may be slower. The big speed gains come with large, complex objects or populations, but in most scenes you will probably cross that threshold pretty quickly. The alpha testers have found that the complexity doesn't need to be very high to get the benefits of ray tracing.

Quote
Micropolygonal rendering seems to also look better, aswell. Ray tracing grassclumps seems to me like using very low quality settings in the old MP renderer. They are barely visible when raytraced. I'm confused.

The ray tracer is more accurate. The micropolygon renderer tends to make thin parts of objects appear thicker than they should be. It's unfortunate that they don't look exactly the same, but I can't make the ray tracer completely match the old look. To get the best quality that wouldn't be desirable anyway.

Quote
P.S. I'm not complaining, not by any means, just confused. Thanks for the input and help. :-[

Not at all :)  I know these are big changes that need explaining well.


jo

Hi guys,

I'm not sure what the issue with the potential problems (not sure if they are problems exactly) some people are seeing but I thought I would say something about the general differences between having raytrace objects on and off, and expand a bit on what dandelO and T-U are saying. When we first added the raytrace objects option I spent quite a lot of time doing comparisons between both modes so I feel qualified to speak about this at least :-).

Generally speaking the raytracer gives a more accurate depiction of objects. The micropolygon renderer tends to make fine details blockier than the raytracer. This can make a raytraced scene look less "dense" but if you do a few comparisons you will find the raytraced images look much better. A good thing to compare is leaves silhouetted against the sky. Even for more general objects than plants there can be a quality improvement.

There are some differences between how shadows are renderered by the raytracer and micropolygon renderer. Here again the raytracer will give more accurate results although there are more cases with this that I found I preferred the "less correct" results from the micropolygon renderer. OTOH if I wasn't comparing the two I probably would never have noticed the differences!

Another advantage of the raytracer is that it gives much higher quality results with lower AA settings in a shorter time. I had to push the AA settings for non-raytraced object renders way up to get about the same quality as a raytraced render.

The tradeoff with the raytracer is that although it gives better results quicker it of course doesn't do actual displacement. It does take displacement information and convert it into bump information, but that doesn't give quite the same effect as actual displacement. If the displacement information is important then you would want to use the micropolygon renderer.

I found that for the objects I was testing with, which didn't have large displacements, the lack of displacement wasn't too much of a problem in anything except closer objects. I think many people would have come to this conclusion already though. I do think that it would be useful to have the option of specifying raytracing on/off on a per-object basis so you could have hero objects and foreground objects with displacement. In the future we would like the raytracer to support displacement though.

Regards,

Jo

jo

Hi Andy,

Quote from: AndyWelder on October 04, 2011, 11:58:45 AM
Let me rephrase the question posed here: Why do object parts not show in a render though they are clearly visible in the 3D preview with " Show as wireframe" checked?

The wireframe display shows the outline of the polygons in the model. As dandelO said, it doesn't show any texturing information. Imagine an extreme case where you have a model but assigned fully transparent alpha maps to the whole model. The model would show up in the 3D Preview as a wireframe but nothing would appear in the full render.

Regards,

Jo

Kadri


Thanks Jo and Martin.
Martin i remember that thread now. Strange i forget the difference of the renderer's so quick!

dandelO

#22
Quote from: jo on October 04, 2011, 10:26:28 PM
... There are some differences between how shadows are renderered by the raytracer and micropolygon renderer. Here again the raytracer will give more accurate results although there are more cases with this that I found I preferred the "less correct" results from the micropolygon renderer. OTOH if I wasn't comparing the two I probably would never have noticed the differences! ...

Regards,

Jo

Doink! I'm now quite confused myself over something you just said, Jo. ^^
Aren't all shadows rendered by the ray tracer?

*EDIT: The renderer option(checked on by default) to 'do ray traced shadows' will completely remove any cast shadows, from geometry or atmosphere.
All that is left after unchecking this option is that the side of a surface facing the light(for example) will be lit and the side away from the light will appear dark, unlit by the direct light, as direct light can't reach the opposite side. All cast shadows are omitted by unchecking 'do ray traced shadows'. I've spent some time testing these settings before and I thought I understood what was happening there, until now! :D ::)

AndyWelder

Look what happens while you're working: You miss everything that's going on! ::)
@ dandelO: I never did mention walli's objects, I was talking about the pine trees that I created, they're the only objects of which I have this level of information. And yup, you're right: Because the needles are small objects the resulting tree-files are huge indeed (Over 100MB) I could create needles with even more details/polygons but because of the resulting crazy filesize I didn't. The only reason I did create pines with the current  level of detail is that I tried to make them needles appear in my render. Now I know what's going on I can cut back on the level of detail and distribution of the needles.
@ Jo: Thank you for this information; very helpful I think though I will have to read this a couple of times more to fully understand.
QuoteThe wireframe display shows the outline of the polygons in the model. As dandelO said, it doesn't show any texturing information.
Hmmm.... Like I said, the needles are objects but let me see if I can make chocolate of it (as they say over here) later tonight after re-reading this a couple of times.
"Ik rotzooi maar wat aan" Karel Appel

dandelO

Hi, Andy. Sorry, man, I assumed(insert ass comment here) that you meant the NWDA pines because that's the ones you had in the preview shots in the first posts here that you were experiencing the problems with.

And... Wow! You're a braver man than I to have modelled individual needles over an entire tree to use in TG. That'd probably shut me down in a second! :D Hope you get the issues fixed. :)

AndyWelder

QuoteI assumed(insert ass comment here) that you meant the NWDA pines because that's the ones you had in the preview shots in the first posts here
Grin, those are NOT the NWDA pines but my own. I have to admit that the NWDA pines were my inspiration though...
"Ik rotzooi maar wat aan" Karel Appel

dandelO


jo

Hi Andy,

Quote from: AndyWelder on October 05, 2011, 12:48:31 PM
QuoteThe wireframe display shows the outline of the polygons in the model. As dandelO said, it doesn't show any texturing information.
Hmmm.... Like I said, the needles are objects but let me see if I can make chocolate of it (as they say over here) later tonight after re-reading this a couple of times.

I would need to see it but with detailed geometry it could be that the 3D Preview looks denser because of the way the polygons are drawn in wireframe. Let's say the lines used to outline the polygon are 1 pixel thick so drawing a needle might have two lines for the sides which looks like 1 or 2 pixels thick in the preview. However the actual renderer, especially the raytracer, would render that needle much more accurately and it might be less than a pixel on screen. By the time antialiasing and filtering has gone on the needle might not end up being very visible at all.

I've done some work on a smooth shaded mode for the 3D Preview. With the smooth shaded mode the interior of the polygons is filled, as opposed to wireframe where a line is drawn around the edge of the polygons. I've found that with the filled polygons objects with fine detail can look much less dense than wireframe, in fact quite a lot closer to the final render. I should add that the smooth shaded mode probably won't be in the next release of TG2.

Regards,

Jo