Iray Section Plane Caps artifacting bug - is this fixed in 4.15?

mwasielewski1990

So, I'm on DAZ 4.14. Whenever I use Iray Section planes, most of the times the render rolls back to CPU (running out of Vram not possible - RTX 3090 here), crashes DAZ, or renders a black image.

I read on the forum that a workaround is to enable Section Caps - and it indeed works, however... it produces wird artifacts on some surfaces, like hair for example, which is painted in the color selected in the "section caps" option.

Is this fixed in 4.15?

I'm in a middle of a project and I don't want to update DAZ for nothing.

thanks :)

ebergerly

I pretty much never use Iray Section Planes/Caps, but for what it's worth...

Just added a section plane to a random scene (I'm using 4.15), and it works fine. I can move and rotate it all over the place in Iray preview and no problem (see first image). I then enabled the Section Cap, and the result is in the second image. I assume the purpose of the cap is to close off any enclosed mesh it opens with a fake face which has the color that you set. Not sure why anyone would want that, but anyway...

For the image I posted, you'd think it would close off the outer room object and you wouldn't see anything inside, but apparently not. It paints the inner surfaces orange.

But for the most part it does seem to close off any separate mesh the plane slices, with some exceptions. Note the blanket on the bed is in orange (the cap color) even though the plane didn't slice any part of it. As well as the picture on the wall. But for the enclosed objects, like the bed and the other objects, as you slice them it does close them off.

So I'm not sure what logic it's using to decide what to close off and color orange. But seeing that the room object itself is colored orange on the inner walls makes me think it's determining the direction of the face normals as it slices, and thinks the room is inside-out or something. So yeah, it seems like it's kinda doing what it's supposed to, but in some cases not so much.

Although I've never really figured out the purpose of the section plane, and especially the caps. I suppose if you want to render the inside of an object. But I'd just take the surface I wanted to make transparent and turn the opacity to zero.  

mwasielewski1990

ebergerly said:

I pretty much never use Iray Section Planes/Caps, but for what it's worth...

Just added a section plane to a random scene (I'm using 4.15), and it works fine. I can move and rotate it all over the place in Iray preview and no problem (see first image). I then enabled the Section Cap, and the result is in the second image. I assume the purpose of the cap is to close off any enclosed mesh it opens with a fake face which has the color that you set. Not sure why anyone would want that, but anyway...

For the image I posted, you'd think it would close off the outer room object and you wouldn't see anything inside, but apparently not. It paints the inner surfaces orange.

But for the most part it does seem to close off any separate mesh the plane slices, with some exceptions. Note the blanket on the bed is in orange (the cap color) even though the plane didn't slice any part of it. As well as the picture on the wall. But for the enclosed objects, like the bed and the other objects, as you slice them it does close them off.

So I'm not sure what logic it's using to decide what to close off and color orange. But seeing that the room object itself is colored orange on the inner walls makes me think it's determining the direction of the face normals as it slices, and thinks the room is inside-out or something. So yeah, it seems like it's kinda doing what it's supposed to, but in some cases not so much.

Although I've never really figured out the purpose of the section plane, and especially the caps. I suppose if you want to render the inside of an object. But I'd just take the surface I wanted to make transparent and turn the opacity to zero.  

Many thanks for elaborating the problem.

I want to use section planes to get more light from a HDRI onto an indoor scene.

As for section Caps:  I only used them to get rid of the crashing bug....

Could you please just hit render and see what you get? My Iray preview renders okay too, but once I hit the actual Render button, it crashes, or renders the image black.

The only thing I would like to verify is if I could use Section planes without caps safely in 4.15 (without crashes, drops to CPU and other horrors).

ebergerly

Y'know, the more I think about it the more it seems that the logic the cap feature uses depends a lot on the composition of the mesh. Stuff like surface normals, whether each object is totally enclosed, etc.

For example, in my image above the room itself is not a totally enclosed object. The wall that the camera is looking thru doesn't exist, and I sliced the room with the section plane. Since the room object is not enclosed maybe it said "Oh wait, no orange cap for the room since it's not an enclosed object. One of the walls doesn't exist".

As far as the other objects that are orange-capped (blanket, painting, etc.), maybe they also are like the room, not fully enclosed objects, and they have unconnected faces or normals pointing in strange ways. 

In any case, I'm not sure I'd assume that there's anything that needs fixing as far as the cap feature, but I'd be more inclined to question the individual objects and how their mesh is configured.  

ebergerly

It renders fine (section caps disabled) on my GTX-1080ti plus RTX-2070 Super. No weird memory spikes. BTW, did you check your log file to see what it says? Also, keep in mind it may be scene-dependent, so just because it works in my scene doesn't mean you don't have some other issues going on that might cause even an upgrade to 4.15 to go bad...

Also, I'm trying to figure how you can use the section cap feature and still get the HDR lighting inside the capped object(s)? When it does the orange cap does it still admit light as if the cap didn't exist? These cap thingy's really have me scratching my head. 

mwasielewski1990

ebergerly said:

It renders fine (section caps disabled) on my GTX-1080ti plus RTX-2070 Super. No weird memory spikes. BTW, did you check your log file to see what it says? Also, keep in mind it may be scene-dependent, so just because it works in my scene doesn't mean you don't have some other issues going on that might cause even an upgrade to 4.15 to go bad...

Also, I'm trying to figure how you can use the section cap feature and still get the HDR lighting inside the capped object(s)? When it does the orange cap does it still admit light as if the cap didn't exist? These cap thingy's really have me scratching my head. 

Many thanks for the info, I'll update to 4.15 and see what I get :)

As for HDRI's - simply place the section planes just outside of your camera shot (so they're not visible) - on the sides and on the top (so three in total, you could also do the bottom one) - this way you'll get a 3-way HDRI light coverage. The planes are going to cut elements of your scene that are not visible in the camera shot, thus unblocking the way for HDRI light. This can be done by hand, but there also is a product for this:

https://www.daz3d.com/interior-light-pro-for-filament-and-iray

"The Iray culling camera has a slider attached to the camera that allows you to choose how much of your scene is culled. Once your scene around the camera is invisible, ambient light from the chosen HDRI can cast inwards and illuminate your scene."

ebergerly

Yes, I understand the role of the section plane, as is shown in the image(s) I posted. But my question was regarding the section CAP, which, after the section plane has opened the mesh to allow HDR light in, the cap (if enabled) seems to cover that opening with a color (orange in this case). So the question was "if the cap covers the opening you made with the plane, is that just a visual trick or does it cover over the section plane opening and block the HDR light?". You said the fix for the section plane crashing was to use the cap feature, and I'm trying to make sense of that. 

 

Richard Haseltine

ebergerly said:

Yes, I understand the role of the section plane, as is shown in the image(s) I posted. But my question was regarding the section CAP, which, after the section plane has opened the mesh to allow HDR light in, the cap (if enabled) seems to cover that opening with a color (orange in this case). So the question was "if the cap covers the opening you made with the plane, is that just a visual trick or does it cover over the section plane opening and block the HDR light?". You said the fix for the section plane crashing was to use the cap feature, and I'm trying to make sense of that.

The section plane cap makes an otherwisewatertight volume fully watertight. It's designed to work like a cut-away drawing (the description seems to offer the possibility of using more general shapes for cutting, but currently it's a Henry Ford-like any shape you want as long as it's an infinate plane).