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pozley

CAD conversion, Phong shading issue

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Hi Guys,

 

So i have converted an .STP file to .OBJ using MOI3D. The geometry comes out nicely, however i am using a warp deformer on this object and the phong shading isn't great...

Whats weird is it seems fine when modeling but as soon as i render you can see clearly it's not smooth.

 

Any advice would be greatly appreciated

 

Thanks,

Jack

 

 

Screenshot 2020-05-18 at 20.55.05.png

Screenshot 2020-05-18 at 20.55.20.png

Screenshot 2020-05-18 at 20.56.21.png

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What's the phong tag / normal tag doing for that object ?

 

CBR

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  • Here are some screenshots. One is me deleting the normal tag, the other is me deleting the Phong tag. You can see when i delete the phong i get that shading you see in the render, which makes me think it's not doing anything?

     

     

    Screenshot 2020-05-18 at 21.59.53.png

    Screenshot 2020-05-18 at 22.00.05.png

    Screenshot 2020-05-18 at 22.00.30.png

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    Does the object have MOI generated 'normal tags' ? If so, those are going to be irrelevant (wrong) as soon as you  deform the gemetry. Delete any on the geometry above and see what happens.

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    One thing you may want to do is select all the points and hit "Optimize".   Whenever I see rendered quads that show triangular shading, then there is probably some overlapping points at the corners.

     

    Just a thought.

    Dave

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    The way CAD Normal tags work with Cinema is that they require a phong as well, so if you delete either it won't work, because deleting just the Normal will leave you with a mesh you can't shade properly, and if you delete the phong then your surfaces won't be smoothed at all. This is the sword of Damocles that hangs over anyone trying to use CAD meshes in a regular DCC. Your model needs to look as exactly as you want it rendered when it first arrives in Cinema, because anything you do to that mesh subsequently (other than texturing it) will be compromising the surfaces, and normally the only solution to that is a rebuild / or retopo. In this case the model really isn't that hard to build in Cinema using SDS poly modelling, so I'd just do that.

     

    CBR

     

     

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    2 hours ago, Cerbera said:

    The way CAD Normal tags work with Cinema is that they require a phong as well, so if you delete either it won't work, because deleting just the Normal will leave you with a mesh you can't shade properly, and if you delete the phong then your surfaces won't be smoothed at all. This is the sword of Damocles that hangs over anyone trying to use CAD meshes in a regular DCC. Your model needs to look as exactly as you want it rendered when it first arrives in Cinema, because anything you do to that mesh subsequently (other than texturing it) will be compromising the surfaces, and normally the only solution to that is a rebuild / or retopo. In this case the model really isn't that hard to build in Cinema using SDS poly modelling, so I'd just do that.

     

    CBR

     

     

    But doesn't all graphics software calculate the shading based upon the angle between the normal vector and the light ray coming from the camera?  The phong tag uses that angle to determine how to shade that polygon....if the angle is more than the angle limit set in the phong tag, it does not get smoothed.

     

    I just figured that was how all programs do it because...well...it sort of makes sense.  You need the normal vector and the phong tag smooth any shading but you make it sound that C4D is unique and that is why modeling needs to be redone if you are importing from other programs. 

     

    So how to other programs do it?

     

    I don't mean to question, just looking to learn from you sir.  I sit at the feet of the master. :respect:

     

    Dave

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    14 minutes ago, 3D-Pangel said:

    you make it sound that C4D is unique and that is why modeling needs to be redone if you are importing from other programs. 

    No, I didn't mean that Cinema was unique in that respect - remodelling will be necessary in every DCC, unless the surface arrives perfectly ready to render (materials excepted) out of the export dialogue... it is subsequent changes to the model in the DCC that break the Phong / Normal tag combo, and I'd imagine every app has a slightly different way of dealing with that. I don't know how the different apps cope with this in the later incarnations, but presume they struggle, because otherwise I wouldn't get so many jobs that were retopo'ing CAD meshes ! But Cinema notably can't deal with it though without a hell of a lot of manual help (ie deleting all the shading tags, and adding a new phong and defining your edge breaks again). 

     

    CBR

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  • Thanks For the replys guys. So it seems like it's not going to be as easy as i'd hoped.

     

    So if i delete the normal and phong tag and then add a new phong tag, how do i go about defining the edge breaks? Is it difficult to do? Would it be easier to re model it from scratch?

     

    Also If it helps these are the settings when exporting the file from MOI3d to .obj

    Screenshot 2020-05-19 at 20.44.47.png

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    You may want to up the geometry a bit...change the angle to 6 and see how that looks.

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