Custom model format face smoothing

IsaacYousuf · March 29, 2016, 2:42pm

Hello. I am trying to get my binary model format to export from Blender with smooth faces. To do this I’ve referenced Blender exporter, and I think I have it down.

When I reached the importing into jME3.1 part I couldn’t find out how the smoothing is applied. In GitHub the OBJLoader skips over the “s 1” flag which is what marks a group of verts as smooth.

My question is how does jME3.1 apply smooth faces from objs? Or what is the class that loads the obj format, if its not “jme3-core.src.plugins.java.com.jme3.scene.plugins.OBJLoader”?

Empire_Phoenix · March 29, 2016, 2:55pm

It does not at all.

For this usually the vertices are shared, with a average normal.
This makes the lighting do a smooth impression instead of a sharp one that happens if you have multiple vertices with different nromals for adjacent triangles.

Momoko_Fan · March 29, 2016, 2:56pm

You should be able to select the model in Blender and then select “Shade Smooth” on the pane left of the 3D View.

IsaacYousuf · March 29, 2016, 2:57pm

So Blender should export the vertices with already averaged normals?

IsaacYousuf · March 29, 2016, 2:59pm

Yeah I’m doing that but this is what my model looks like imported. Must be exporting something wrong…

Momoko_Fan · March 29, 2016, 3:00pm

That model looks smooth to me. What is it supposed to look like?

IsaacYousuf · March 29, 2016, 3:01pm

Like this:

Momoko_Fan · March 29, 2016, 3:09pm

Just making sure, you did select “Export Normals” when saving the OBJ right?

IsaacYousuf · March 29, 2016, 3:11pm

OBJs work fine. I’m working on my own format, for fun. I want to know how/where OBJs calc their smooth faces. Is it already averaged in exported OBJ or is it done on import?

Momoko_Fan · March 29, 2016, 3:19pm

The normals are exported here:
https://git.blender.org/gitweb/gitweb.cgi/blender-addons.git/blob/HEAD:/io_scene_obj/export_obj.py#l534

jME does not do any averaging, it writes the normals verbatim:

github.com

jMonkeyEngine/jmonkeyengine/blob/master/jme3-core/src/plugins/java/com/jme3/scene/plugins/OBJLoader.java#L508-L513


Vertex v0 = f.verticies[0];
Vertex v1 = f.verticies[1];
Vertex v2 = f.verticies[2];
posBuf.position(v0.index * 3);

Blender is capable of calculating per-vertex normals (as opposed to per-face). That’s what you’re seeing when the model is displayed in the preview. You need to make sure you’re exporting per-vertex normals and not per-face normals.

IsaacYousuf · March 29, 2016, 3:30pm

Okay this is what I have thought. I don’t get where smoothing is happening there.

Check out:
https://git.blender.org/gitweb/gitweb.cgi/blender-addons.git/blob/HEAD:/io_scene_obj/export_obj.py#l473

Is this pair being sorted that makes it smooth? I cannot pinpoint it.

Momoko_Fan · March 29, 2016, 3:35pm

But the model is still smooth when you enable “Keep Vertex Order”.

IsaacYousuf · March 29, 2016, 3:38pm

Interesting, now I’m more lost. So where is the smoothing happening?

Or does it not happen on export. Does hitting the smooth faces alter the model itself?

nehon · March 29, 2016, 3:41pm

Yes, it recomputes the normals for all the vertices.

IsaacYousuf · March 29, 2016, 3:42pm

Weird. So why is my exporter messing it up? If I don’t do anything for cases where face.use_smooth it just comes out flat…

Momoko_Fan · March 29, 2016, 4:06pm

Are you exporting vertex normals or triangle normals?

IsaacYousuf · March 29, 2016, 4:42pm

“loop” normals? I am learning using the IQM format. This is the function that I inherited into my exporter:(minus the alpha vertcol and materials)

github.com

lsalzman/iqm/blob/master/blender-2.74/iqm_export.py#L810


            flags = int(animspec[4])
        except:
            flags = 0
        framedata = collectAnim(context, armature, scale, bones, actions[animname], startframe, endframe)
        anims.append(Animation(animname, framedata, fps, flags))
    armature.animation_data.action = oldaction
    scene.frame_set(oldframe)
    return anims

 
def collectMeshes(context, bones, scale, matfun, useskel = True, usecol = False, filetype = 'IQM'):
    vertwarn = []
    objs = context.selected_objects #context.scene.objects
    meshes = []
    for obj in objs:
        if obj.type == 'MESH':
            data = obj.to_mesh(context.scene, False, 'PREVIEW')
            if not data.polygons:
                continue
            data.calc_normals_split()
            coordmatrix = obj.matrix_world

IsaacYousuf · March 29, 2016, 5:19pm

Nevermind. I’m just going to use the OBJ method.

Edit: I got it. I had messed something up.