I'm trying to learn Redshift in Houdini 18.0.499, but I'm having trouble rendering a simple smoke sim that I cached. Does anyone have anyone have any idea why it shows up bigger in the Redshift IPR than in the Scene View? It shows up correctly if I try and render it in Mantra. I tried a bunch of things including starting a new project and re-sourcing just the sim from scratch which is what you see in the screenshot. I also tried opening the scene in Houdini 18.0.460 but I got the same result.

It looks like to me that you're just zoomed in on the render. Move your mouse into the render window and use the mouse wheel to zoom out until you see the edge of the frame.

Thanks for the reply, but I most certainly would not be posting on here if that were the case. As you can see in the screenshot. I’m using the Redshift Render view which has fixed scale set to 100% at 1280x720, and that custom desktop I made is specifically designed to fit that ratio in that exact space. So, zooming in or out on the render does not fix or change anything. Not only that, but the same thing happens in the Houdini Render View in different versions of Houdini. I feel like it’s got something to do with that volume cache because other geometry shows up correctly, including the source on the original setup I had going. For example, if I were to make a box it would also show up properly. And, as I said before it renders properly in Mantra. Or, perhaps the fact that I set it up in Mantra first caused some bug to show up. Either way, it seems like I should be able to easily convert a Mantra scene to a Redshift scene without having to rebuild and recache everything no?

One thing I notice is your Redshift Renderview says <Auto>, you sure it's really showing cam1?

I definitely tried changing the cam1 back and forth between auto and cam1, but since there's only 1 camera in the scene I think it defaults to cam1 and I get the same result. It seems to be a really strange issue, or perhaps a bug. I've been using Redshift for a couple years in C4D now, so I'm no stranger to the way the renderer works, and at first I was excited by how well it seems to be integrated into Houdini, until I ran into this issue. I've never seen Redshift, in any app, show one object bigger in the render view than it is in the scene, but show all others the right size. I'm doing a render right now, so I can't post a screenshot proving this, but I'll try it again when my render's over.

Weird. If you're allowed to share the scene file I'd be happy to have a look.

I’d love to. As soon as I’m done with this render, I’ll open it up again and have a look to make sure I’m not missing something. I can upload it with the cache, if you don’t mind downloading it, but I’m worried that the problem might exist within the cache itself. And, if you recache it on your end it might work. So, I wanna try and recache on my end even though it seems like that really shouldn’t be the issue. If it still shows up huge after the new cache I’ll definitely upload it cause I wouldn’t know where to go from there.

This is what one of the admins on the Redshift forums had to say:

“…these problems come from working with grids that have different voxel size inside the same vdb object, for example, the velocity grids. Redshift doesn’t support this, and although the plugin has some workarounds, they don’t always work.

Removing these grids or converting the whole volume from “vdb” to “volume” primitives usually resolve this issue…”

I don’t know anything about grid size to VDB voxel size relationship, so any information about that would be useful, or if anyone knows of a good tutorial that covers it that would be great. Anyway, I’ve uploaded the file. I assume you’ll have to re-cache everything. I hope that it’s not something as simple as caching it again once it’s set up in Redshift. Do you think switching from Mantra to Redshift could be the thing that cause the issue?

Ah.

You are caching the volumes at 2x the resolution. Change “Render with take” on your cache node from “HQ” to “Current” and the render will match what you see in the preview.

(Middle click the dopimportfield1 node and you'll notice the voxel sizes are 0.066667 and 0.033333. Now middle click the cache node and look the voxel sizes have halved. Redshift obv gets confused by this and renders the volume at double the size rather than double the resolution.)

Or you could render at HQ, but add a Convert VDB node and see if that helps Redshift as per the forum admins suggestion. Or maybe Redshift will get it if you stick to one voxel size, say 0.033333 (0.016667 after caching as HQ).

Edit: Or not?

Interesting! I guess I'll have to be careful when using different quality takes. I wonder why Steven doesn't mention that as a potential gotcha in Volumes II? It seems like such a frustrating thing to try and troubleshoot when you're still learning because it works in mantra and then all of a sudden you switch to Redshift and the volume's huge and there appears to be no reason why. Anyway, I'll try messing with it again when I get a minute. Big thanks for taking a look.

So, switching Render With Take to current didn't seem to work for me. The guys on the Redshift forum told me to disable the rest fields, which I did in the Initial Data section of the smokeobject and the rest field section of the pyrosolver. Once I resimmed that seemed to do the trick even with the take set to HQ.

However, does anyone have any idea why the ground plane cyc won't render? I thought it was maybe because I built it for Mantra, so I tried to rebuild from scratch and a normal grid SOP shows up in the Redshift RenderView, but as soon as I convert it to NURBS and add an edit SOP it disappears in the render. Pretty frustrating that it's so hard to render this basic stuff, but I'm sure I'm missing something obvious.

Happy to hear you worked it out! And sorry if appearing somewhat bombastic in my suggestions, seemed to do the trick on my end though.

No worries. So weird that switching takes actually worked on your end, but in the end I wouldn’t have wanted to switch takes. I definitely want to render at 600 and not 300. 300 was just meant to speed up working…

I guess I just had to switch that NURBS geo to polys to get the BG cyc to show up properly. But, I’m still having trouble getting displacement to work on it. This time it shows up correctly in the Redshift IPR, but not in the bucket rendering. There’s just some ugly noise instead. I’m definitely gonna ask the Redshift guys about this, again…

However, I’m starting to wonder if it’s worth it to learn RS for Houdini if there’s so many annoying issues like this that work out of the box in C4D. It’d be so much faster and more pleasurable to export the smoke to VDB and render in Cinema. Also, the lack of the C4D shader node is kind of a deal breaker for me.

I use that node so often to mix Maxon noises and plug procedural textures into dome lights and other things… For being the procedural emperor, Houdini seems to be lacking in Redshift proceduralism…

Then again, there’s got to be a solution and if I just move back to C4D I’m not learning Houdini, which is kind of the point. Maybe there’s a way to achieve some similar noise mixing abilities in COPs, which is a context I haven’t really explored.

I’m still not sure how to plug procedural textures into a dome light though. I imagine that might involve some scripting. Would you happen to know how to go about achieving any of that functionality?

BenjaminMarkus
Then again, there’s got to be a solution

With Houdini, Redshift, and volumes, that's not necessarily the case unfortunately. Which is a shame because otherwise it's great.

BenjaminMarkus
No worries. So weird that switching takes actually worked on your end

I might have done additional tweaks and then forgot, I don't know.

Yeah I guess depending on the scene C4D might be a better option for rendering. But, I’m still gonna hound the Redshift guys about this stuff. These are really basic things that should work.