mental ray refuses SubD rendering

[Lil_Mick]

it's because MR doesn't render sub-D's at all, as far as I know at least.

~J

[ooz]

yes it does... i just rendered a subD cube in maya... maybe u have a wierd version of maya

[BillSpradlin]

"sided and 3 sided faces (some 5 sided),"

There's your problem. mental ray will not render subD meshes that are not all quad, all tri, or all n-gon, in other words, no mixed sided meshes. So quad (preferred) out your mesh before rendering, otherwise mental ray will not render it.

[ooz]

s#*t! is there a button or something that converts it to quads? or do i have to go in and do that manually??

[BillSpradlin]

You can use the collapse hierchy function which will quad everything out and additionally create a large amount of uneeded geometry. Polysmooth before converting will also quad everything out, but again will create a large amount of uneeded geometry. It's always a good idea to keep everything in quads to begin with, although some will argue that, for rendering SubD's in mental ray it's a must.

[ooz]

i guess i have to go in and do it manually, although i tried the quadrangulate command under polygons menu which seems to do absolutely nothing...

oh well, thanks for the help billspradin, i appreciate it

[BillSpradlin]

The automatic tools that Maya has for some polygon operations leave much to be desired. No problem, and good luck.

[stuh505]

mental ray in Maya 6.5 won't render subdivision surfaces with non-quads in base mesh

Only base meshes made of quads are supported.

Workaround

To convert to quads, select Subdiv Surfaces > Collapse Hierarchy > http://localhost:4448/Maya6.5/en_US/gfx/optbox.gif and set the number of levels to 1.

Partial creases rendering as full creases

Partial creases of subdivision surfaces are not supported in this version of mental ray for Maya. They will be rendered as full creases.

As you can see, according to the manual, you are also limited to full creases.

Now...I'm having a different kind of problem -- MR renders the subdiv, but ignores all the creases! I've had this problem on MR 3.3 and MR 3.4

Has anyone else had this problem, or have a solution for me?

[ninus3d]

Why on earth do you not just convert it to polygon?
Youd be left with 0 problems as far as rendering concerns

[ooz]

i modelled it initially in polygons. but in rendering i want it smooth, so i converted it to subDs.

if i just applied smooth to it then it wont be undoable if i delete history, but subDs i can always just convert back to polys whenever i want.

and i think subDs look way better than smoothed polygons

[ninus3d]

yeah, that is true, or atleast I agree 100%!
However, what I ment was convert the subd's back to polygons MAINTAINING the exact same detail in the mesh...
Itl be exactly the same in smoothshaped, however may require a quite high tesselation thus ending up with aloooot of faces but itl atleast be renderable in MR :)

[ooz]

so ur saying i convert to subD then convert back to Polys with a level 2?

that will be more precise but too heavy... like u said...

i think ill just go in and do a manual cleanup, it might waste a lot of my time but it will save in render times and interactive time

[stuh505]

in my situation, I modelled in subD...went to subd level 2 and converted to polys...then converted back to subd so that I could render it with fully subdivided surface. but like I said, MR is giving me problems and wont render the smoothed subd surface. the whole reason I brought it into maya was just to render it as a subD...:/

[BillSpradlin]

That's totally inefficent way of going about solving a very simple problem. Edge looping ftw.

[PixelVampire]

In Softimage MR can render 3+4 sided faces. Why can't it be implemented in Maya?

Should I assume that by Maya 7 it will be possible?

[cpan]

mray can render 3+4 sided faces, but only polygonal ones. The subd must be fixed

[PixelVampire]

mray can render 3+4 sided faces, but only polygonal ones. The subd must be fixed

Yes you are right but I was talking about Subd. My fault for not writing clearly.

[augustus]

In Softimage MR can render 3+4 sided faces. Why can't it be implemented in Maya?

Should I assume that by Maya 7 it will be possible?


As far as I know, XSI sends subdivs to mr as smoothed polygons. You can use smooth proxy in Maya if you don't need creases.

[ninus3d]

wich again most likely renders the reason for using subds useless... well, not entirely but heavy or not, converting back to poly seems to be the best way!
Get more power to renderwith and the heavy tesselation wont stop you ;)

[stuh505]

Get more power to renderwith and the heavy tesselation wont stop you ;)

The memory of your system sets a practical limit on how detailed your scenes can be.

If all your objects must suddenly be, let's say...1000 times heavier...then your scene is going to be that many times smaller.

[cpan]

I think it could be done a script that converts Subdivs to polygons at rendertime. There is a section in the Common Render Globas where you can write a procedure that executes before rendering, so this is't impossible.

[a23]

hello ooz,

if a smooth render of your character is all you want and aren't using the sub-d hierarchy then the best thing is to get rid of your n-gons. don't worry about your mesh being 3 and 4 sided polys. instead of converting your mesh to a maya sub-d leave it a poly object and just use the mental ray approximation editor (menu > window > rendering editors > mental ray > approximation editor).

Select your object and then create a new subdivision approximation. A new node is attached to your mesh (e.g, mentalraySubdivApprox1). For starters leave it parametric, but be sure to
change the mesh conversion from none to "Quads to Triangles". This way you don't have to waste your RAM for Maya to tesselate the mesh, but instead MR will do it at render time.

This worked on all our productions with mixed 3-4 sided polymeshes.

AndY

[ooz]

a23, i think im gonna try that, sounds a little advanced for me but if thats what its gonna take, then ill do it... ill let u know

WOW...thanks a23, this is too good to be true... not only did it fix the problem, but now i dont need to worry about heavy objects to get nice renders...

is there a catch?

[a23]

hey ooz,

great that everything worked out for you the way i described it!
there's no catch to this, just too many users not taking a look into MR for Maya ;-)
Now that you got it working nicely, try playing with the different approximation modes.

I suggest going with either LDA or Spatial/Fine, but i'll leave this as an exercise for you to read in the Maya/MR docs ;-)

Glad i could help.

AndY

[mattcioffi]

the only issue with converting quads to tris is that a poly object with mostly quads will render stiffer using that tri based algorithm. also doesn't solve 5sided issue right? a way to collapse the hiearchy without loosing the base mesh is to have a polysmooth node in history and a mr subdiv approximation attached to the polymesh - don't convert to subdiv in maya. only invoke the polysmooth node at rendertime. works awesome. this also allows you to use UV smoothing for the first couple subdivisions.

well anyway -another way of getting what you want.

converting to polygons in maya doesn't work if you're using displacement maps -- specifically on mesh with uv seams. subdivs are a must.

[poly-phobic]

As you can see, according to the manual, you are also limited to full creases.



Now...I'm having a different kind of problem -- MR renders the subdiv, but ignores all the creases! I've had this problem on MR 3.3 and MR 3.4



Has anyone else had this problem, or have a solution for me?

[/list]

MR in maya only renders full creases, not partial creases.

[eekie]

Hi,

Noob here so pls filter this advice through your 3d logic processors 1st...

what i did was just to collapse the SubD Heirachy and MentalRay accepted it

converting it to poly/NURBS yielded an awful result

Goodluck!

[ASWDesign]

When ever i model something in polygons and convert to sub-D to smooth it does the same. i get around this problem by Converting my sub-D shape to NURBS...it keeps the shape the same but make sure you Group it (Ctrl + G) because it will just be patchs of geo, and if its big...you might get a problem rendering but if its a small little charicatar try that.

Works for me

ASW

[mattcioffi]

converting to nurbs creates lots of tiny little cracks in your model - some don't show up - but some will. converting to polys in that instance is probably best.

i said something in my last post about UV smoothing and polysmooth node: MR subdivs smooth UVs everywhere but at the edges no need to use maya polysmooth node for this.

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