For the fun, a Photos cube

cvp

Thanks

I still try to define a shape like a tetrahedron (4 triangular faces) using SCNGeometrySource but I've problems with array of vertices.
I try to convert this code in Pythonista, I'm sure @JonB could do it in two minutes and I'm fighting against errors for hours.
My dream is to be able, one day in a very far future, to help JonB in something 🙄

SCNVector3 verts[] = { SCNVector3Make(0, 0, 0), SCNVector3Make(1, 0, 0), SCNVector3Make(0, 1, 0) };
SCNGeometrySource *src = [SCNGeometrySource geometrySourceWithVertices:verts count:3];
int indexes[] = { 0, 1, 2 };
NSData *datIndexes = [NSData dataWithBytes:indexes length:sizeof(indexes)];
SCNGeometryElement *ele = [SCNGeometryElement geometryElementWithData:datIndexes primitiveType:SCNGeometryPrimitiveTypeTriangles primitiveCount:1 bytesPerIndex:sizeof(int)];
SCNGeometry *geo = [SCNGeometry geometryWithSources:@[src] elements:@[ele]];

scj643

I actually need people to help make an API for scenekit so we can do this type of stuff with a python AI

cvp

I would like to help but I think I know not enough objective c for that...
When I program in objc, I spend hours before it works.

scj643

https://github.com/scj643/objc_tools is my repo

cvp

I know your repo, often checked...

momorprods

hey, digging out this old topic - did you have chance into the triangle mesh generation?

I have started converting the Obj-c snippet above, but it crashes Pythonista at the geometrySourceWithVertices call. Probably my bad, but I’m clueless about how to fiw this:

verts=[SCNVector3(0, 0, 0), SCNVector3(1, 0, 0), SCNVector3(0, 1, 0)]

src = SCNGeometrySource.geometrySourceWithVertices_count_(POINTER(verts),3)

cvp

@momorprods No, sorry, I didn't success...

JonB

It wouldn't be POINTER here. Try byref.

JonB

Actually, verts must be a ctypes array, not a python list.

momorprods

oh ok thanks, going to try that and keep you posted!

momorprods

Made this, but still crashing. Am I making another noob mistake?

verts=[0.0,0.0,0.0 , 1.0,0.0,0.0 , 0.0,1.0,0.0]
arr = (ctypes.c_float * len(verts))(*verts)
src = SCNGeometrySource.geometrySourceWithVertices_count_(byref(arr),3)

cvp

@momorprods Perhaps this (at least, no crash 😀)

class SCNVector3(Structure):
	_fields_ = [('x', c_double), ('y', c_double), ('z', c_double)]

And

    verts=[SCNVector3(0, 0, 0), SCNVector3(1, 0, 0), SCNVector3(0, 1, 0)]
    verts_array = (SCNVector3 * len(verts))(*verts)
    SCNGeometrySource = ObjCClass('SCNGeometrySource').geometrySourceWithVertices_count_(
    verts_array,len(verts),
    restype=c_void_p,
    argtypes=[POINTER(SCNVector3), c_ulong],)

momorprods

wooohoooo thanks!!

momorprods

Making some good progress thanks to your help. But I’m getting a last crash on the very last instruction - any idea?

#triangle generation
verts=[SCNVector3(0, 0, 0), SCNVector3(1, 0, 0), SCNVector3(0, 1, 0)]
verts_array = (SCNVector3 * len(verts))(*verts)

src = ObjCClass('SCNGeometrySource').geometrySourceWithVertices_count_(
    verts_array,len(verts),
    restype=c_void_p,
    argtypes=[POINTER(SCNVector3), c_ulong],)
    
indexes=[0,1,2]
indexes_array = (c_ulong*len(indexes))(*indexes)
datIndexes = ObjCClass('NSData').dataWithBytes_length_(indexes_array,len(indexes_array))
 
ele=ObjCClass('SCNGeometryElement').geometryElementWithData_primitiveType_primitiveCount_bytesPerIndex_(datIndexes,SCNGeometryPrimitiveTypeTriangles,1,4)
   
# CRASH Here: 
geo = ObjCClass('SCNGeometry').geometryWithSources_elements_(src,ele)

cvp

@momorprods I've read that indices must contain a first element with the number of points but I don't know if it is true.
sources and elements must be arrays
But I have also a crash with my code
See faultlog below but I can't solve the problem, sorry

    verts = [SCNVector3(0, 0, 0), SCNVector3(1, 0, 0), SCNVector3(0, 1, 0)]
    verts_array = (SCNVector3 * len(verts))(*verts)
    SCNGeometrySource = ObjCClass('SCNGeometrySource').geometrySourceWithVertices_count_(
    verts_array,len(verts),
    restype=c_void_p,
    argtypes=[POINTER(SCNVector3), c_ulong],)
    sources = NSArray([SCNGeometrySource])
    
    indices = [3,0,1,2]	# number points and their indices
    indices_data = ns(indices)
    # primitiveType = 0 for triangle
    # primitiveCount = 1
    SCNGeometryElement = ObjCClass('SCNGeometryElement').geometryElementWithData_primitiveType_primitiveCount_bytesPerIndex_(indices_data,0,1,4)
    elements = NSArray([SCNGeometryElement])
    
    geometry = ObjCClass('SCNGeometry').geometryWithSources_elements_(sources, elements)

Fatal Python error: Aborted

Current thread 0x0000000100d62b80 (most recent call first):
File "/var/containers/Bundle/Application/E4751F4F-64A4-4BE6-AB9D-9C9564715002/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/objc_util.py", line 773 in call
File "/private/var/mobile/Containers/Shared/AppGroup/668A7D98-7216-47ED-917D-AA0B6173167E/Pythonista3/Documents/test6.py", line 51 in demo
File "/var/containers/Bundle/Application/E4751F4F-64A4-4BE6-AB9D-9C9564715002/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/objc_util.py", line 1066 in OMMainThreadDispatcher_invoke_imp

Thread 0x000000016fa5f000 (most recent call first):
File "/var/containers/Bundle/Application/E4751F4F-64A4-4BE6-AB9D-9C9564715002/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/objc_util.py", line 898 in call
File "/var/containers/Bundle/Application/E4751F4F-64A4-4BE6-AB9D-9C9564715002/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/objc_util.py", line 1095 in new_func
File "/private/var/mobile/Containers/Shared/AppGroup/668A7D98-7216-47ED-917D-AA0B6173167E/Pythonista3/Documents/test6.py", line 76 in <module>

Objective-C exception details:

NSInvalidArgumentException: -[SCNGeometrySource count]: unrecognized selector sent to instance 0x283276100

JonB

this works

from ctypes import *
from objc_util import *

class SCNVector3(Structure):
    _fields_ = [('x', c_double), ('y', c_double), ('z', c_double)]

verts=[SCNVector3(0, 0, 0), SCNVector3(1, 0, 0), SCNVector3(0, 1, 0)]

SCNVector3Array3=SCNVector3 * len(verts)
verts_array=SCNVector3Array3(*verts)
SCNGeometrySource = ObjCClass('SCNGeometrySource')

s=SCNGeometrySource.geometrySourceWithVertices_count_(byref(verts_array),len(verts),restype=c_void_p,argtypes=[POINTER(SCNVector3Array3), c_ulong],)

cvp

@JonB Yes, but in my code,,the crash was in

    geometry = ObjCClass('SCNGeometry').geometryWithSources_elements_(sources, elements)

cvp

@momorprods @JonB No crash with

    verts = [SCNVector3(0, 0, 0), SCNVector3(1, 0, 0), SCNVector3(0, 1, 0)]     
    SCNVector3Array3=SCNVector3 * len(verts)
    verts_array=SCNVector3Array3(*verts)
    SCNGeometrySource = ObjCClass('SCNGeometrySource')
    s = SCNGeometrySource.geometrySourceWithVertices_count_(byref(verts_array),len(verts),restype=c_void_p,argtypes=[POINTER(SCNVector3Array3), c_ulong],)
   
    indexes=[0,1,2]
    indexes_array = (c_ulong*len(indexes))(*indexes)
    datIndexes = ObjCClass('NSData').dataWithBytes_length_(indexes_array,len(indexes_array))
    # primitiveType = 0 for triangle
    # primitiveCount = 1  
    e = ObjCClass('SCNGeometryElement').geometryElementWithData_primitiveType_primitiveCount_bytesPerIndex_(datIndexes,0,1,4)
    
    geometry = ObjCClass('SCNGeometry').geometryWithSources_elements_([s],[e])
	```

Edit: but nothing visible

cvp

@momorprods I'm not sure if you should take in account the length of c_ulong
Just an idea, rally not sure.
Anyway, Scene stays blank 😢

    #indexes=[0,1,2]
    indexes = [c_ulong(0),c_ulong(1),c_ulong(2)]
    indexes_array = (c_ulong*len(indexes))(*indexes)
    #datIndexes = ObjCClass('NSData').dataWithBytes_length_(indexes_array, len(indexes_array))
    datIndexes = ObjCClass('NSData').dataWithBytes_length_(indexes_array, len(indexes_array)*sizeof(c_ulong))
    # primitiveType = 0 for triangle
    # primitiveCount = 1  
    #e = ObjCClass('SCNGeometryElement').geometryElementWithData_primitiveType_primitiveCount_bytesPerIndex_(datIndexes,0,1,4)
    e = ObjCClass('SCNGeometryElement').geometryElementWithData_primitiveType_primitiveCount_bytesPerIndex_(datIndexes,0,1,sizeof(c_ulong))

momorprods

@cvp @JonB thanks for your help, I am going to investigate that empty scene stuff.