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Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 9:51 am
by smicha
Hi TIG,
When I zoom out my model strange lines occur (screenshot attached). When I zoom an object in, it is plain as should be. What could be a reason for this pattern?

Sebastian

Image

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 10:14 am
by smicha
Hi TIG,
One more question. I created a simple box in Sketchup and painted it with color_000. After importing it in octane, strange pattern is still visible and there are 2 materials: one is "color_000" (this is correct ) and "default material". What is the "default material"? If I assign any type of material to this "default material" nothing changes.

Image

Regards,

Sebastian

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 10:29 am
by smicha
TIG,
First problem solved :) I increased a value of rayepsilon in mesh preview kernel. BTW what is the default/desired value of rayepsilon?

Sebastian

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 10:36 am
by face
Rayepsilon have nothing to do with it, you scaling is wrong.
Scale the mesh down should fix the problem...

face

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 10:39 am
by smicha
Thank you face. Could you please be more precise what should I do?

smicha

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 11:04 am
by Refracty
Octane works in meters.
So lets say you model a mobile phone in the units melemeters in Rhino or so. Then you have to scale it times 0.001 (or divide the size by 1000).
That should work.
Just scale it down.

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 11:10 am
by smicha
Refracty,
do you mean scaling a model in sketchup/rhino...? In the example you gave shouldn't I multiply - not divide?

smicha

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 11:28 am
by TIG
Your OCS Preferences should look something like this [always meters!?]
CapturePREFS.PNG

The exporter always uses 'meters' even if you are using some other units in the SKP. Meters is always the units exported into the OBJ.
If you make an OBJ file by some other means, then you must ensure its settings are to use meters and triangulate faces etc too...
My test SKP looks like this.
CaptureSKP.PNG

My Exporter dialog settings look like this
CaptureDIA.PNG
[the fact it automatically shows unchangeable 'mm' as the native-units is academic - that IS the units I an working in BUT the OBJ is always made in 'm' irrespective of the units - showing 'native-units' is simply a requirement of RSL's exporter dialog standardization - some applications would need you to set this - SKP does not]. Your OCS preference's units should always be set to 'meters'.
My test OCS looks like this.
CaptureOCS.PNG


The reason there is always a 'Default_Material' [even if it doesn't appear to be used] is that every exported face needs a material - even if it doesn't have a material in the SKP. That material lists first as it's always the first material defined in the MTL. If you haven't given a face a material the 'default' is used in the SKP - as set in your SKP's current Style. Here I've made the default-front-face-material 'creamy'. The smaller cube has no material applied in the SKP and so in the OBJ and thence in the OCS it takes that creamy 'Default_Material'. The larger cube has the white 'color_000' material. If a material wasn't specified for a face I suspect that the OCS would render it in a 'black' material [0,0,0]. At least with this approach the OCS rendering looks like the SKP - e.g. if you have missed a material off a particular face, rather than a 'black-hole'...

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 5:48 pm
by smicha
TIG,
Thank you for your reply. Please forgive me being to precise and posting many screen shots. I still don't get some aspects of importing mesh from sketchup.


I set units sketchup to centimiters
Image

but as you said this doesn't matter.

My purpose is to create a cube 1x1x1m. So I created a cube 1x1x1 cm - not meter. As Refracty had said I have to /scale divide my model by 100 and I just did it.

Image

My settings are as yours

Image

I also read my mesh preview resolution from octane

Image

and set it into Sketchup Exporter

Image

After exporting I got well placed cube but "target" and "up" are strange (why?)

Image


As I tried to rotate or move my object it just gone outside the preview area

Image


So I reset camera view to default and manually corrected target and up as follows

Image

Now I applied "brick material" form LiveDB

Image

and my cube looks good (I repeat that this is 1x1x1 cm cube - not 1x1x1 m).

Image

So if textures form Live DB look good on scaled 100 times mesh and Sketchup Exporter "knows" what units are predefined in Sketchup, why do we have to scale our mesh manualy? It is just a matter of scaling by 100, even if I choose millimeters (Am I wrong?). Now I understand what Refracty was talking about (or I don't :) )

Please take a look what happens if I create 1x1x1m and 1x1x1 mm cubes:

Image

Image


Object gone after moving it

Image

And after resetting view I can easily control its location

Image


But materials from Live DB need to be corrected (or my mesh scaled by a 100 down)


Image

Same for 1x1x1mm cube

Image

and for such scales I am loosing DOF (depth of field) although I set aperture to minimum - again scaling is required

Image


and Live DB texture are also too big

Image

Summarizing my questions:

1. Do I have to manually scale my meshes by 100? If I build a cube 1x1x1 m it must be resized to 1x1x1 cm?

2. What am I doing wrong that "target" and "up" I have to set manually to 0 0 0 and 0 1 0 respectively.


Again please forgive describing it in explicit detail and thank you so much for your time and help.


Sebastian


PS. Forgive me also my English.

Re: Strange pattern on imported obj

PostPosted: Sun Nov 06, 2011 10:53 pm
by roeland
The camera values are coming from the exporter. The up vector seems to be chosen to be perpendicular to the viewing direction. The camera navigation in Octane interprets the up vector as the vertical up direction in the scene (usually [0 1 0]).

The camera rotates around the point given in "target". You can pick a target point on the cube with the zoom picker tool.

The brick texture is an image texture, so its scaling doesn't depend on the size of the cube, but on the UV mapping. The scaling of volumetric textures on the other hand depends on the size. The size of the cube seems to be correct.

And in the black render halfway your post the camera position somehow ended up inside the cube.

--
Roeland