A Blender Python script to export meshes for OpenGL tinkering

blenderExportIndexed.py

# Export script that takes the selected mesh and puts its vertex data (position, normal, uv)
# and indices of triangles on the clipboard and in the console
#
# > Why not just export to obj and read that?
# Proper obj reading requires you to deal with a lot of stuff:
# - separate indices for position, normal and uv, that need to be duplicated for an OpenGL VBO
# - 1-indexing
# - materials, objects, other things
#
# https://docs.blender.org/api/blender_python_api_2_73_release/bpy.types.MeshPolygon.html
# https://docs.blender.org/api/blender_python_api_2_73_release/bpy.types.MeshVertex.html

import bpy  
from mathutils import Vector

obj = bpy.context.active_object 
bpy.ops.object.mode_set(mode = 'EDIT')
bpy.ops.mesh.quads_convert_to_tris(quad_method='BEAUTY', ngon_method='BEAUTY')
bpy.ops.object.mode_set(mode = 'OBJECT')

separator = " "
datastr = "" ## Vertices:\n

# Convert a vector to a comma-separated string
def vecStr(vec, decimals=4):
    result = ""
    for i in vec:
        result += str(round(i, decimals)) + separator
    return result

uvlayer = obj.data.uv_layers.active
hasUv = uvlayer is not None # can be forced to True, then it will add 0,0 uv's if needed
nverts = len(obj.data.vertices)
nfaces = len(obj.data.polygons)
vertlists = [[] if hasUv else [Vector((0,0))] for i in range(nverts)]
faceSub = [[-1, -1, -1] for i in range(nfaces)]
    
for fn, face in enumerate(obj.data.polygons):
    for vn, vid, loop in zip(range(3), face.vertices, face.loop_indices):
        if hasUv:
            uv = uvlayer.data[loop].uv
            i = 0
            while i < len(vertlists[vid]):
                if (vertlists[vid][i] == uv):
                    break
                i+=1
                
            if i == len(vertlists[vid]):
                vertlists[vid].append(uv)
                
            faceSub[fn][vn] = i
        else:
            faceSub[fn][vn] = 0

vertstart = [0 for i in range(nverts+1)]

for vn, vert in enumerate(obj.data.vertices):
    vertstart[vn+1] = vertstart[vn] + len(vertlists[vn])
    if hasUv:
        for uv in vertlists[vn]:
            datastr += vecStr(vert.co)
            datastr += vecStr(vert.normal)
            datastr += vecStr(uv)
            datastr += "\n"
        pass
    else:
        datastr += vecStr(vert.co)
        datastr += vecStr(vert.normal)
        datastr += "\n"
        

datastr = str(vertstart[-1]) + separator + str(len(obj.data.polygons)) + "\n" + datastr
#datastr += "# Faces:\n"

for fn, face in enumerate(obj.data.polygons):
    for i in range(3):
        vn = face.vertices[i]
        datastr += str(vertstart[vn] + faceSub[fn][i]) + separator
        
    datastr += "\n"
    
print(datastr)
bpy.context.window_manager.clipboard = datastr