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Brötje
11-15-2012, 01:44 AM
I have some problems with MDD files.

I did some simulations for falling stalactites and saved those to MDD. When it's time to render, I see all these strange spikes in my geometry. They do not show up in VPR, but they do in the final render.
I know that MDD can have some noise when the points are to far removed from the origin, but moving the whole scene closer is not an option.

Surely there has to be something that can be done?

RebelHill
11-15-2012, 03:02 AM
Sounds like a node match/subdiv order or similar issue. MDDs (or rather the different tools for applying them to a mesh) seem to work better in some circumstances than others. Give the MDD nodes a go, they seem pretty good most of the time.

Brötje
11-15-2012, 03:04 AM
I will try this! Thank you :D

Brötje
11-15-2012, 04:09 AM
Seems to be an error in the render engine. Wireframe looks alright in the viewport. VPR renders it ok, but the render engine renders it spiky. I've imported the geometry and the MDD in Modo and it seems to work fine.

I think it's time for a bug report.

dpont
11-15-2012, 04:20 AM
Seems to be an error in the render engine. Wireframe looks alright in the viewport. VPR renders it ok, but the render engine renders it spiky. I've imported the geometry and the MDD in Modo and it seems to work fine.

Also make sure that your SubD Render Level matches
your SubD Display Level.

Denis.

Brötje
11-15-2012, 04:24 AM
Also make sure that your SubD Render Level matches
your SubD Display Level.

Denis.

It's a poly object, no SubDs used.

dpont
11-15-2012, 04:44 AM
You may try another MDD Player,
or try to regenerate/rescan the imported MDD in Layout.

Denis.

Brötje
11-15-2012, 04:49 AM
You may try another MDD Player,
or try to regenerate/rescan the imported MDD in Layout.

Denis.

I'm going to sound ignorant, but... what other MDD player? I used the one in the node editor, the regular one...

dpont
11-15-2012, 05:24 AM
I'm going to sound ignorant, but... what other MDD player? I used the one in the node editor, the regular one...

Natively, you first have the choice between the Displacement MD Reader plugin
and the nodal displacement version,
also as free other tools,
in DP Kit, you can try the MDD Pointer or MDD Cache nodes
in DP Motion Designer, the MDD Pointer Displacement plugin,
that said no pretention this can solve your issue.

Once you can get a correct MDD in preview mode,
you can bake it in Layout with the displacement MD Baker
to see if its MDD has the same issue.

Denis.

Brötje
11-15-2012, 05:48 AM
I think the MDD was correct in the first place.

I've attached some images to show you.

1. OpenGl ( with MDD )

109165

2. VPR ( with MDD )

109166

3. Render ( with MDD )

109167

On top of that, Modo displays and renders the geometry correctly. Hence I think it's a bug somewhere.

dpont
11-15-2012, 06:01 AM
I think the MDD was correct in the first place.
...
On top of that, Modo displays and renders the geometry correctly. Hence I think it's a bug somewhere.


Anyway if you report it,
your content object and mdd file are needed
for debugging.

Denis.

Brötje
11-15-2012, 06:18 AM
Yeah, I guess I'm going to report it. I did a render in Modo and it turned out just fine. It's reportin' time!

Brötje
11-15-2012, 06:53 AM
Bug reported.

Brötje
12-02-2012, 02:41 PM
Hi guys,

The good people at Newtek have solved the issue. I'm posting the reply here, so anyone can look at it when they run into the same problem.


VPR and OpenGL triangulate the mesh before rendering. The object contains large complex polygons (inside the outer skin). When they are deformed, they can become degenerate (non-flat and/or twisted from some camera angles). This causes the ray tracer to incorrectly intersect the polygons causing the reported spikes. To solve this problem, triangulate the meshes in modeler or via a plug-in prior to using the MDD deformation.

The classic camera also renders this scene correctly because it scan converts the polygons which is more robust than the ray intersection algorithm for complex polygons.

So this is really "due to ray tracing"

jasonwestmas
12-02-2012, 03:00 PM
yeah, unfortunately LW render doesn't automatically triangulate the polys and non planar quads render artifacts. At least that's how it was last time I checked.

jwiede
12-02-2012, 03:18 PM
Well, good to know about VPR triangulating the meshes, is this explicitly spelled out (and highlighted/noted) in the docs anywhere?