iOS remove faces and vertices from .obj file - ios

Question

I use SceneKit to display .obj file. But to get an .obj file I use SDK from a sensor, so this sensor scans the arm of a man and returns the .obj file as a result. But when I load the .obj file, there are a lot of not proper parts (part of chair, part of the surface and so on), I need to remove these parts of the object, so as a result I has to see only the arm of the man.
So for example I want to select a rectangle or a sphere and to remove all vertices and faces in this sphere.
Are there any SDK or frameworks in iOS to do that?
P.S. I tried nineveh and some other frameworks, but they can only view objects, they can't edit them.
Edit
I found the code to manipulate vertices (it merges vertices from different child nodes) in SceneKit. Can I use the same approach to find vertices I need to remove (that are inside my rectangle) or it will be very slow with 65 K vertices?
//
// VertexManager.m
// Test
//
#import "VertexManager.h"
#import <SceneKit/SceneKit.h>
#import <GLKit/GLKit.h>
#implementation VertexManager
+ (SCNNode *) flattenNodeHierarchy:(SCNNode *) input
{
SCNNode *result = [SCNNode node];
NSUInteger nodeCount = [[input childNodes] count];
if(nodeCount > 0){
SCNNode *node = [[input childNodes] objectAtIndex:0];
NSArray *vertexArray = [node.geometry geometrySourcesForSemantic:SCNGeometrySourceSemanticVertex];
SCNGeometrySource *vertex = [vertexArray objectAtIndex:0];
SCNGeometryElement *element = [node.geometry geometryElementAtIndex:0]; //todo: support multiple elements
NSUInteger primitiveCount = element.primitiveCount;
NSUInteger newPrimitiveCount = primitiveCount * nodeCount;
size_t elementBufferLength = newPrimitiveCount * 3 * sizeof(int); //nTriangle x 3 vertex * size of int
int* elementBuffer = (int*)malloc(elementBufferLength);
/* simple case: here we consider that all the objects to flatten are the same
In the regular case we should iterate on every geometry and accumulate the number of vertex/triangles etc...*/
NSUInteger vertexCount = [vertex vectorCount];
NSUInteger newVertexCount = vertexCount * nodeCount;
SCNVector3 *newVertex = malloc(sizeof(SCNVector3) * newVertexCount);
SCNVector3 *newNormal = malloc(sizeof(SCNVector3) * newVertexCount); //assume same number of normal/vertex
//fill
NSUInteger vertexFillIndex = 0;
NSUInteger primitiveFillIndex = 0;
for(NSUInteger index=0; index< nodeCount; index++){
#autoreleasepool {
node = [[input childNodes] objectAtIndex:index];
NSArray *vertexArray = [node.geometry geometrySourcesForSemantic:SCNGeometrySourceSemanticVertex];
NSArray *normalArray = [node.geometry geometrySourcesForSemantic:SCNGeometrySourceSemanticNormal];
SCNGeometrySource *vertex = [vertexArray objectAtIndex:0];
SCNGeometrySource *normals = [normalArray objectAtIndex:0];
if([vertex bytesPerComponent] != sizeof(float)){
NSLog(#"todo: support other byte per component");
continue;
}
float *vertexBuffer = (float *)[[vertex data] bytes];
float *normalBuffer = (float *)[[normals data] bytes];
SCNMatrix4 t = [node transform];
GLKMatrix4 matrix = MyGLKMatrix4FromCATransform3D(t);
//append source
for(NSUInteger vIndex = 0; vIndex < vertexCount; vIndex++, vertexFillIndex++){
GLKVector3 v = GLKVector3Make(vertexBuffer[vIndex * 3], vertexBuffer[vIndex * 3+1], vertexBuffer[vIndex * 3 + 2]);
GLKVector3 n = GLKVector3Make(normalBuffer[vIndex * 3], normalBuffer[vIndex * 3+1], normalBuffer[vIndex * 3 + 2]);
//transform
v = GLKMatrix4MultiplyVector3WithTranslation(matrix, v);
n = GLKMatrix4MultiplyVector3(matrix, n);
newVertex[vertexFillIndex] = SCNVector3Make(v.x, v.y, v.z);
newNormal[vertexFillIndex] = SCNVector3Make(n.x, n.y, n.z);
}
//append elements
//here we assume that all elements are SCNGeometryPrimitiveTypeTriangles
SCNGeometryElement *element = [node.geometry geometryElementAtIndex:0];
const void *inputPrimitive = [element.data bytes];
size_t bpi = element.bytesPerIndex;
NSUInteger offset = index * vertexCount;
for(NSUInteger pIndex = 0; pIndex < primitiveCount; pIndex++, primitiveFillIndex+=3){
elementBuffer[primitiveFillIndex] = offset + _getIndex(inputPrimitive, bpi, pIndex*3);
elementBuffer[primitiveFillIndex+1] = offset + _getIndex(inputPrimitive, bpi, pIndex*3+1);
elementBuffer[primitiveFillIndex+2] = offset + _getIndex(inputPrimitive, bpi, pIndex*3+2);
}
}
}
NSArray *sources = #[[SCNGeometrySource geometrySourceWithVertices:newVertex count:newVertexCount],
[SCNGeometrySource geometrySourceWithNormals:newNormal count:newVertexCount]];
NSData *newElementData = [NSMutableData dataWithBytesNoCopy:elementBuffer length:elementBufferLength freeWhenDone:YES];
NSArray *elements = #[[SCNGeometryElement geometryElementWithData:newElementData
primitiveType:SCNGeometryPrimitiveTypeTriangles
primitiveCount:newPrimitiveCount bytesPerIndex:sizeof(int)]];
result.geometry = [SCNGeometry geometryWithSources:sources elements:elements];
//cleanup
free(newVertex);
free(newNormal);
}
return result;
}
//helpers:
GLKMatrix4 MyGLKMatrix4FromCATransform3D(SCNMatrix4 transform) {
GLKMatrix4 m = {{transform.m11, transform.m12, transform.m13, transform.m14,
transform.m21, transform.m22, transform.m23, transform.m24,
transform.m31, transform.m32, transform.m33, transform.m34,
transform.m41, transform.m42, transform.m43, transform.m44}};
return m;
}
GLKVector3 MySCNVector3ToGLKVector3(SCNVector3 vector) {
GLKVector3 v = {{vector.x, vector.y, vector.z}};
return v;
}
#end

Answer 1

No. You'll want to use a 3d tool like Blender, Maya, 3ds Max, or Cheetah 3D.