Rendering dynamic cloth: How to avoid the polygons showing?



  • I learned from some thread in this forum that the cloth simulation works better with triangle polygons than squares or rectangles. So I decided to leave the Poser default props alone and made my own hires plane in Blender, creating a 60x60 square polygons plane, triangulated it and exported it as OBJ. After importing it into Poser, I applied a subdivision of 2 for good measure. Then I used the cloth room with silk settings to let the cloth sink down over a cube on the ground. The result looks pretty awesome, as you can see in a detail view here:
    0_1494279340529_Drape_subdiv2.png

    After applying a satin material to the drape I rendered it with my usual settings and this is what I got:
    0_1494279393774_Drape_render.png

    As you can see, the satin material looks fine, but despite the high polygon count, the polys still show up prominently.

    Does anybody have an idea how to give dynamic cloth a smoother look?


  • Poser Ambassadors

    My suggestions would be - try running the morph brush set to smooth over the draped mesh; using more subdivision to reduce the appearance of the artefacts; starting with a mesh that has much less of a regular grid structure should make artefacts less obvious.



  • If you look at your first image, you lost your tris when you subdivided it. Try subdividing in blender instead if you want tris. I drape a lot of stuff even quads. I find the smaller the polygon, to less you see the rough edges. If you still get them after you get to a ridiculous level, run your smoothing morph brush over them. It does wonders and is probably the easiest brush to use.


  • Poser Team

    The easiest way to do triangulated mesh in Blender for cloth in Poser is to do something like this.
    0_1494281868852_mesh.jpg

    At the stage in the screenshot. There are no faces at all.
    Start with a plane, delete the face only.
    Then build a lattice that looks like this.
    This is tedious without a script, you do a lot of subdividing, joining them with F etc.
    The trick is to make this an extremely dense lattice of triangles like you see.
    Once you get the lattice built, select the whole thing and then face the whole thing.
    (A to select all the vertices, then F to fill in all the triangles with the normals the same direction.)

    Then dont subdivide it in Poser, and it will drape based on triangle size.
    Here is a blend file for you to look at and play around with.
    Rename accordingly then extract the zip.

    0_1494282325609_cloth.zip.txt



  • @shvrdavid An even easier way to make a triangle mesh in Blender is:
    Add Mesh > Cylinder and select 'vertices=6', 'cap = triangle fan'.
    Delete the vertices for the lower cap so you're only left with the upper cap.
    Subdivide as many times as you want/need - Blender subdivides triangles into smaller triangles using Edit mode,W,Subdivide
    0_1494318379530_hextri.jpg
    (and they're "...those crazy radiating/hexagonal triangles, those will give the most natural folding and bending" recommended way back p.175 of "Secrets Of Figure Creation With Poser 5". Nowadays Delauney triangulation seems to be the way to go - Blender link that might be of interest regarding that https://blenderartists.org/forum/showthread.php?353148-blender-irregular-mesh)


  • Poser Team

    that works too



  • Thanks everybody for your suggestions! I think I have to dig into Blender a bit more to get this finally working.

    So as far as I see, there is no other way but throwing more polygons at it?
    Can anyone explain then why Poser renders people and conforming clothing so much smoother even if they have a much smaller polygon count?


  • Poser Ambassadors

    IMO, it's all about edge flow. A mesh can only bend at the edges, so if you have a mesh that needs to bend or deform in a certain way e.g. an elbow, you would build it with that in mind. Edge loops would be positioned to support the deformation required, so the bend would be smooth. If a mesh bends against the edge flow however the result is ugly jagged artefacts - try using the morph brush diagonally on a grid to see the effect.

    Cloth can bend in all kinds of ways - & that's the problem. The deformation is not specific, so if the mesh it is made from has a regular edge flow then at some points the mesh will bend against the edge flow which will result in noticeable jaggies. Therefore the ideal mesh for dynamic cloth would be more irregular in structure - while artefacts would still occur they are less likely to be as obvious due to being less regular.

    Does that make sense?



  • @caisson Makes perfect sense! Thank you very much.
    I never used the morph brush before, but I will try in my next dynamic cloth render.


  • Poser Ambassadors

    @oldenburg said in Rendering dynamic cloth: How to avoid the polygons showing?:

    So as far as I see, there is no other way but throwing more polygons at it?
    Can anyone explain then why Poser renders people and conforming clothing so much smoother even if they have a much smaller polygon count?

    It's not a lack of polys. What you're seeing is due to the quads becoming twisted nonplanar, which makes each quad's normal noticeably different from its neighbors, and so with Poser's smoothing (which averages the normal over the poly and compares it to the averaged normal of the adjacent polys) you see shadowing at polygon boundaries.

    In your modeling program, select all polys and triangulate. Export the triangulated version of the mesh to Poser for dynamic cloth use. Triangles are inherently coplanar, so no smoothing artifacts. :-)

    You could even do this with your existing scene: Export the draped cloth in the final frame as an OBJ. Use Blender (or any other modeler) to select all polys and triangulate. Export the triangulated OBJ. Import that triangulated pre-draped OBJ into Poser.


  • Poser Ambassadors

    Select the cloth object.
    Go to properties.
    Enable Smooth Polygons and set crease angle to 180°.
    Render in FireFly with Smoothing enabled.

    In SuperFly? Use a SubD on the cloth.



  • @oldenburg Another point about the high polygon density for dynamic cloth as compared to people/conforming cloth, and related to caisson's: With people and conforming clothing the main bending/deforming is also limited to specific areas, and the polygon mesh is often denser in that area. Whereas the bending/deforming in dynamic cloth can be anywhere, in any orientation, and much more extreme.

    This BlenderArtists thread is worth a look if you're interested in irregular triangular meshes and Delauney triangulation - https://blenderartists.org/forum/showthread.php?353148-blender-irregular-mesh No easy answers there I'm afraid, but a good start for an investigation!


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