I have a function which does some array manipulation on an NSMutableArray. Somehow after a couple of loops of the while function the values inside 2 local variables are total garbage. They are not being assigned or manipulated anywhere. Here's how:
Here's the function:
-(void) normalize_path:(NSMutableArray *)path tool:(Tool)tool
{
NSUInteger last_accepted_point_index = 0;
NSUInteger current_point_index = 1;
while(current_point_index < [path count]){
VPoint * p1, * p2;
[[path objectAtIndex:last_accepted_point_index] getValue:&p1];
[[path objectAtIndex:current_point_index] getValue:&p2];
//float distance = [self distance_between:p1 and:p2];
// if(distance < MIN_POINT_DISTANCE){
// [path removeObjectAtIndex:current_point_index];
// }else{
// float opacity = tool.max_opacity - distance * tool.opacity_sensitivity;
// opacity = opacity <= tool.min_opacity ? tool.min_opacity : opacity;
// p2->opacity = opacity;
// float thickness = tool.max_thickness - distance * tool.thickness_sensitivity;
// thickness = thickness <= tool.min_thickness ? tool.min_thickness : thickness;
// p2->thickness = thickness;
// last_accepted_point_index = current_point_index;
// //current_point_index++;
// }
}
}
And it's called only in one place like so:
//...
[self normalize_path:opath tool:pen];
//...
Every run creates different values. I am confounded! What is going on here?
I think that this may be a memory issue which you can fix by removing the & from in front of p1 and p2 in the getValue: call. It's difficult to be totally sure as you haven't said what VPoint is, but normally this code would look like this:
VPoint p1, p2;
[[path objectAtIndex:last_accepted_point_index] getValue:&p1];
[[path objectAtIndex:current_point_index] getValue:&p2];
This would then set p1 and p2 to the actual values. Your distance between function would then not take references but the actual values of p1 and p2 (if you want to pass references as you are doing now, you'd put & in front of p1 and p2 in the distance callBetween method call.
Related
Is it possible to increment a variable's value by passing this variable to some function parameter, so that variable's value changes e.g.
int y=0;
void someFunc(int a);
somefunc(y+50);
NSLog(#"y=#f",y);
prints "y = 50"
You can do it this way
someFunc(y=y+50);
someFunc(y=+50);
but is there more elegant way accomplishing this, using pointers maybe? e.g
someFunc(*y+50);
This is the snippet of my code where I want to accomplish this
-(void)drawRect:(CGRect)rect
{
CGFloat currentX = 0;
CGFloat currentY = height / 2;
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(ctx, 5);
CGContextSetStrokeColorWithColor(ctx, [UIColor blackColor].CGColor);
CGContextSetFillColorWithColor(ctx, [UIColor redColor].CGColor);
CGContextMoveToPoint(ctx,currentX, currentY);
CGContextAddLineToPoint(ctx, currentX=currentX+50, currentY - 200);
CGContextAddLineToPoint(ctx, currentX=+50, currentY - 200);
CGContextAddLineToPoint(ctx, currentX=+50, currentY - 200);
CGContextAddLineToPoint(ctx, currentX=+50, currentY - 200);
CGContextDrawPath(ctx, kCGPathStroke);
}
I want to keep that currentX's value being updated everytime I increment it in the function parameter. Get it?
You can do this by passing a pointer to the variable. This is called an "out parameter" or "call by reference":
void someFunc( int * a, int o )
{
…
*a = *a + o;
}
int y = 0;
someFunc( &y, 50 );
// y is y+o
Either you need to change the value before calling the function, in which case you do:
x = x + something;
func(x);
or if you need to change the value after calling the function, you do like this:
func(x);
x = x + something;
Common sense.
NOTE: never write code like func(x=something) with the assignment inside the parameter list. Because in case you get a habit of doing so, you will soon be writing order-of-evaluation bugs such as func(x, x=something) // BAD, unspecified behavior.
Alternatively, if you need to change the value inside the function, you could pass its address:
void func (int* param)
{
*param = something;
}
...
func(&x);
But you can obviosuly only do this if the function is written by you. This doesn't seem to be the case here, since those functions are apparently part of some Apple library.
my program is Directx Program that draws a container cube within it smaller cubes....these smaller cubes fall by time i hope you understand what i mean...
The program isn't complete yet ...it should draws the container only ....but it draws nothing ...only the background color is visible... i only included what i think is needed ...
this is the routines that initialize the program
bool Game::init(HINSTANCE hinst,HWND _hw){
Directx11 ::init(hinst , _hw);
return LoadContent();}
Directx11::init()
bool Directx11::init(HINSTANCE hinst,HWND hw){
_hinst=hinst;_hwnd=hw;
RECT rc;
GetClientRect(_hwnd,&rc);
height= rc.bottom - rc.top;
width = rc.right - rc.left;
UINT flags=0;
#ifdef _DEBUG
flags |=D3D11_CREATE_DEVICE_DEBUG;
#endif
HR(D3D11CreateDevice(0,_driverType,0,flags,0,0,D3D11_SDK_VERSION,&d3dDevice,&_featureLevel,&d3dDeviceContext));
if (d3dDevice == 0 || d3dDeviceContext == 0)
return 0;
DXGI_SWAP_CHAIN_DESC sdesc;
ZeroMemory(&sdesc,sizeof(DXGI_SWAP_CHAIN_DESC));
sdesc.Windowed=true;
sdesc.BufferCount=1;
sdesc.BufferDesc.Format=DXGI_FORMAT_R8G8B8A8_UNORM;
sdesc.BufferDesc.Height=height;
sdesc.BufferDesc.Width=width;
sdesc.BufferDesc.Scaling=DXGI_MODE_SCALING_UNSPECIFIED;
sdesc.BufferDesc.ScanlineOrdering=DXGI_MODE_SCANLINE_ORDER_UNSPECIFIED;
sdesc.OutputWindow=_hwnd;
sdesc.BufferDesc.RefreshRate.Denominator=1;
sdesc.BufferDesc.RefreshRate.Numerator=60;
sdesc.Flags=0;
sdesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
if (m4xMsaaEnable)
{
sdesc.SampleDesc.Count=4;
sdesc.SampleDesc.Quality=m4xMsaaQuality-1;
}
else
{
sdesc.SampleDesc.Count=1;
sdesc.SampleDesc.Quality=0;
}
IDXGIDevice *Device=0;
HR(d3dDevice->QueryInterface(__uuidof(IDXGIDevice),reinterpret_cast <void**> (&Device)));
IDXGIAdapter*Ad=0;
HR(Device->GetParent(__uuidof(IDXGIAdapter),reinterpret_cast <void**> (&Ad)));
IDXGIFactory* fac=0;
HR(Ad->GetParent(__uuidof(IDXGIFactory),reinterpret_cast <void**> (&fac)));
fac->CreateSwapChain(d3dDevice,&sdesc,&swapchain);
ReleaseCOM(Device);
ReleaseCOM(Ad);
ReleaseCOM(fac);
ID3D11Texture2D *back = 0;
HR(swapchain->GetBuffer(0,__uuidof(ID3D11Texture2D),reinterpret_cast <void**> (&back)));
HR(d3dDevice->CreateRenderTargetView(back,0,&RenderTarget));
D3D11_TEXTURE2D_DESC Tdesc;
ZeroMemory(&Tdesc,sizeof(D3D11_TEXTURE2D_DESC));
Tdesc.BindFlags = D3D11_BIND_DEPTH_STENCIL;
Tdesc.ArraySize = 1;
Tdesc.Format= DXGI_FORMAT_D24_UNORM_S8_UINT;
Tdesc.Height= height;
Tdesc.Width = width;
Tdesc.Usage = D3D11_USAGE_DEFAULT;
Tdesc.MipLevels=1;
if (m4xMsaaEnable)
{
Tdesc.SampleDesc.Count=4;
Tdesc.SampleDesc.Quality=m4xMsaaQuality-1;
}
else
{
Tdesc.SampleDesc.Count=1;
Tdesc.SampleDesc.Quality=0;
}
HR(d3dDevice->CreateTexture2D(&Tdesc,0,&depthview));
HR(d3dDevice->CreateDepthStencilView(depthview,0,&depth));
d3dDeviceContext->OMSetRenderTargets(1,&RenderTarget,depth);
D3D11_VIEWPORT vp;
vp.TopLeftX=0.0f;
vp.TopLeftY=0.0f;
vp.Width = static_cast <float> (width);
vp.Height= static_cast <float> (height);
vp.MinDepth = 0.0f;
vp.MaxDepth = 1.0f;
d3dDeviceContext -> RSSetViewports(1,&vp);
return true;
SetBuild() Prepare the matrices inside the container for the smaller cubes ....i didnt program it to draw the smaller cubes yet
and this the function that draws the scene
void Game::Render(){
d3dDeviceContext->ClearRenderTargetView(RenderTarget,reinterpret_cast <const float*> (&Colors::LightSteelBlue));
d3dDeviceContext->ClearDepthStencilView(depth,D3D11_CLEAR_DEPTH | D3D11_CLEAR_STENCIL,1.0f,0);
d3dDeviceContext-> IASetInputLayout(_layout);
d3dDeviceContext-> IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
d3dDeviceContext->IASetIndexBuffer(indices,DXGI_FORMAT_R32_UINT,0);
UINT strides=sizeof(Vertex),off=0;
d3dDeviceContext->IASetVertexBuffers(0,1,&vertices,&strides,&off);
D3DX11_TECHNIQUE_DESC des;
Tech->GetDesc(&des);
Floor * Lookup; /*is a variable to Lookup inside the matrices structure (Floor Contains XMMATRX Piese[9])*/
std::vector<XMFLOAT4X4> filled; // saves the matrices of the smaller cubes
XMMATRIX V=XMLoadFloat4x4(&View),P = XMLoadFloat4x4(&Proj);
XMMATRIX vp = V * P;XMMATRIX wvp;
for (UINT i = 0; i < des.Passes; i++)
{
d3dDeviceContext->RSSetState(BuildRast);
wvp = XMLoadFloat4x4(&(B.Memory[0].Pieces[0])) * vp; // Loading The Matrix at translation(0,0,0)
HR(ShadeMat->SetMatrix(reinterpret_cast<float*> ( &wvp)));
HR(Tech->GetPassByIndex(i)->Apply(0,d3dDeviceContext));
d3dDeviceContext->DrawIndexed(build_ind_count,build_ind_index,build_vers_index);
d3dDeviceContext->RSSetState(PieseRast);
UINT r1=B.GetSize(),r2=filled.size();
for (UINT j = 0; j < r1; j++)
{
Lookup = &B.Memory[j];
for (UINT r = 0; r < Lookup->filledindeces.size(); r++)
{
filled.push_back(Lookup->Pieces[Lookup->filledindeces[r]]);
}
}
for (UINT j = 0; j < r2; j++)
{
ShadeMat->SetMatrix( reinterpret_cast<const float*> (&filled[i]));
Tech->GetPassByIndex(i)->Apply(0,d3dDeviceContext);
d3dDeviceContext->DrawIndexed(piese_ind_count,piese_ind_index,piese_vers_index);
}
}
HR(swapchain->Present(0,0));}
thanks in Advance
One bug in your program appears to be that you're using i, the index of the current pass, as an index into the filled vector, when you should apparently be using j.
Another apparent bug is that in the loop where you are supposed to be iterating over the elements of filled, you're not iterating over all of them. The value r2 is set to the size of filled before you append anything to it during that pass. During the first pass this means that nothing will be drawn by this loop. If your technique only has one pass then this means that the second DrawIndexed call in your code will never be executed.
It also appears you should be only adding matrices to filled once, regardless of the number of the passes the technique has. You should consider if your code is actually meant to work with techniques with multiple passes.
First, let me clarify what I mean by "grouped models." I'm not actually sure what the standard terminology for this is. In order to reduce the number of rendering calls, I am grouping multiple models into a single model, and rendering the whole thing with a single call to glDrawElements (using VBOs). In my code, I call this a ModelGroup. I use it for various things, but especially for large groups of geometrically simple objects (like buildings in a city, or particles).
The problem has recently surfaced where my ModelGroups are rendering very slowly. I have isolated the slowdown to the actual call to glDrawElements by putting a timer around it. For instance, my particles used to render ~10k particles (without instancing) at around 2ms or so. I can't recall the exact number, but let's just say the rendering was definitely not the bottleneck as it currently is. As of now, a single call to glDrawElements with 10k particles takes right about 256ms. This performance is only marginally better than rendering the objects each with separate calls to glDrawElements. So, there is clearly a massive burden on the GPU for some reason.
What has changed in my engine:
I recently updated XCode and changed from using EAGLView to using GLKViewController. I changed nothing else in my code between these two very different states of performance. I will say that, in order to migrate over to the use of the GLKViewController, I recreated my project entirely and added all of my source files in. Then I rewrote my game loop to be updated by the GLKViewController's update function. This was a very minor change, however.
Just to be completely clear on what my ModelGroup class does, I will post the function that compiles the added models into the display model which is rendered.
-(bool) compileDisplayModelWithNormals:(bool)updateNormals withTexcoords:(bool)updateTexcoords withColor:(bool)updateColor withElements:(bool)updateElements
{
modelCompiled = YES;
bool initd = displayModel->positions;
// set properties
if( !initd )
{
displayModel->primType = GL_UNSIGNED_SHORT;
displayModel->elementType = GL_TRIANGLES;
displayModel->positionType = GL_FLOAT;
displayModel->texcoordType = GL_FLOAT;
displayModel->colorType = GL_FLOAT;
displayModel->normalType = GL_FLOAT;
displayModel->positionSize = 3;
displayModel->normalSize = 3;
displayModel->texcoordSize = 2;
displayModel->colorSize = 4;
// initialize to zero
displayModel->numVertices = 0;
displayModel->numElements = 0;
displayModel->positionArraySize = 0;
displayModel->texcoordArraySize = 0;
displayModel->normalArraySize = 0;
displayModel->elementArraySize = 0;
displayModel->colorArraySize = 0;
// sum the sizes
for( NSObject<RenderedItem> *ri in items )
{
GLModel *model = ri.modelAsset.model.displayModel;
displayModel->numVertices += model->numVertices;
displayModel->numElements += model->numElements;
displayModel->positionArraySize += model->positionArraySize;
displayModel->texcoordArraySize += model->texcoordArraySize;
displayModel->normalArraySize += model->normalArraySize;
displayModel->elementArraySize += model->elementArraySize;
displayModel->colorArraySize += model->colorArraySize;
}
displayModel->positions = (GLfloat *)malloc( displayModel->positionArraySize );
displayModel->texcoords = (GLfloat *)malloc( displayModel->texcoordArraySize );
displayModel->normals = (GLfloat *)malloc( displayModel->normalArraySize );
displayModel->elements = (GLushort *)malloc( displayModel->elementArraySize );
displayModel->colors = (GLfloat *)malloc( displayModel->colorArraySize );
}
// update the data
int vertexOffset = 0;
int elementOffset = 0;
for( int j = 0; j < [items count]; j++ )
{
NSObject<RenderedItem> *ri = (GameItem *)[items objectAtIndex:j];
GLModel *model = ri.modelAsset.model.displayModel;
if( !ri.geometryUpdate )
{
vertexOffset += model->numVertices;
continue;
}
// reset the update flag
ri.geometryUpdate = NO;
// get GameItem transform data
rpVec3 pos = [ri getPosition];
rpMat3 rot = [ri orientation];
int NoV = model->numVertices;
int NoE = model->numElements;
for( int i = 0; i < NoV; i++ )
{
// positions
rpVec3 r = rpVec3( model->positions, model->positionSize * i );
// scale
rpVec3 s = ri.scale;
r.swizzleLocal( s );
// rotate
r = rot * r;
// translate
r.addLocal( pos );
int start = model->positionSize * (vertexOffset + i);
for( int k = 0; k < model->positionSize; k++ )
displayModel->positions[start + k] = r[k];
if( updateTexcoords )
{
// texcoords
start = model->texcoordSize * (vertexOffset + i);
if( model->texcoords )
for( int k = 0; k < model->texcoordSize; k++ )
displayModel->texcoords[start + k] = model->texcoords[model->texcoordSize * i + k];
}
if( updateNormals )
{
// normals (need to be rotated)
if( model->normals )
{
for( int k = 0; k < model->normalSize; k++ )
{
rpVec3 vn = rpVec3( model->normals, model->normalSize * i );
rpVec3 vnRot = rot * vn;
start = model->normalSize * (vertexOffset + i);
displayModel->normals[start + k] = vnRot[k];
}
}
}
if( updateColor )
{
if( model->colors )
{
start = model->colorSize * (vertexOffset + i);
displayModel->colors[start] = ri.color.r;
displayModel->colors[start + 1] = ri.color.g;
displayModel->colors[start + 2] = ri.color.b;
displayModel->colors[start + 3] = ri.color.a;
}
}
}
if( updateElements )
{
for( int i = 0; i < NoE; i++ )
{
// elements
displayModel->elements[elementOffset + i] = model->elements[i] + vertexOffset;
}
}
vertexOffset += NoV;
elementOffset += NoE;
}
return YES;
}
Just to be complete, here is how I render the particles. Inside the particle field draw function:
glBindVertexArray( modelGroup.displayModel->modelID );
glBindTexture( GL_TEXTURE_2D, textureID );
// set shader program
if( changeShader ) glUseProgram( shader.programID );
[modelViewStack push];
mtxMultiply( modelViewProjectionMatrix.m, [projectionStack top].m, [modelViewStack top].m );
glUniformMatrix4fv( shader.modelViewProjectionMatrixID, 1, GL_FALSE, modelViewProjectionMatrix.m );
[DebugTimer check:#"particle main start"];
glDrawElements( GL_TRIANGLES, modelGroup.displayModel->numElements, GL_UNSIGNED_SHORT, 0 );
[DebugTimer check:#"particle main end"];
[modelViewStack pop];
The two statements that sandwich the glDrawElements statement are the timer I used to measure time between events.
Also, I just wanted to add that I have run on both the device and the iPad simulator 6.1 with the same result. The simulator is slower at performing multiple draw calls, but both are equally slow at calling glDrawElements for a ModelGroup. As far as hardware acceleration is concerned, I have checked to make sure that this performance hit isn't coming as some side effect of a lack of acceleration. I rendered a model read in from a file which contained 1024 cubes (similar to a ModelGroup for a city) which rendered with no problem (no 20ms delay as with 1000 cubes in a ModelGroup).
I believe that I have solved the mystery, in a manner of speaking. It is, after all, still a mystery to me why this solves the problem.
I had been using my own custom enum values for these functions
glEnableVertexAttribArray
glVertexAttribPointer
instead of using the newly (as of iOS 5.0, I think) Apple-specified values that came as part of the GLKViewController class:
GLKVertexAttribPosition
GLKVertexAttribNormal
GLKVertexAttribTexcoord0
Having made this change yielded the kind of performance I expected when calling glDrawElements. My model groups will now render on the order of 0.1 ms as they should, rather than ~20 ms. As I said, I really do not understand exactly why this fixes anything, but it's a solution all the same.
Simple question. What is the best way to turn a CGPoint into a GLKVector?
These structures are identical so it would be nice to be able to reinterpret_cast or memcpy or something like that. My solution below works but hardly seems optimum. I'm creating a GLKVector2 on the stack assigning each member then returning this as a value which is then assigned to another GLKVector.
It's not going to break the bank or anything but there must be a neater way to do this?
GLKVector2 Vector2FromPoint(CGPoint point)
{
GLKVector2 v;
v.x = point.x;
v.y = point.y;
return v;
}
You could try using memcpy in a function like this:
bool vector2ToCGPoint(GLKVector2* s, CGPoint* d) {
memcpy(d, s, sizeof(*d));
}
but then it is probably better to have:
bool copyVector2ToCGPoint(GLKVector2* s, CGPoint* d) {
d.x = s.x;
d.y = s.x;
}
if you really want optimization, you could go for a macro:
#define copyS2D(S,D) (D.x = S.x, D.y = S.y)
so you can do:
CGPoint b;
GLKVector2 a;
vector2FromCGPoint(a, b);
of course, as you know, macros will not be that much type-safe...
GLKVector2 v = GLKVector2Make(point.x, point.y);
I have a graph structure where I am removing edges one by one until some conditions are met. My brain has totally stopped and i can't find an efficient way to detect if removing an edge will result in my graph splitting in two or more graphs.
The bruteforce solution would be to do an bfs until one can reach all the nodes from a random node, but that will take too much time with large graphs...
Any ideas?
Edit: After a bit of search it seems what I am trying to do is very similar to the fleury's algorithm, where I need to find if an edge is a "bridge" or not.
Edges that make a graph disconnected when removed are called 'bridges'. You can find them in O(|V|+|E|) with a single depth-first search over the whole graph. A related algorithm finds all 'articulation points' (nodes that, if removed, makes the graph disconnected) follows. Any edge between two articulation-points is a bridge (you can test that in a second pass over all edges).
//
// g: graph; v: current vertex id;
// r_p: parents (r/w); r_a: ascents (r/w); r_ap: art. points, bool array (r/w)
// n_v: bfs order-of-visit
//
void dfs_art_i(graph *g, int v, int *r_p, int *r_v, int *r_a, int *r_ap, int *n_v) {
int i;
r_v[v] = *n_v;
r_a[v] = *n_v;
(*n_v) ++;
// printf("entering %d (nv = %d)\n", v, *n_v);
for (i=0; i<g->vertices[v].n_edges; i++) {
int w = g->vertices[v].edges[i].target;
// printf("\t evaluating %d->%d: ", v, w);
if (r_v[w] == -1) {
// printf("...\n");
// This is the first time we find this vertex
r_p[w] = v;
dfs_art_i(g, w, r_p, r_v, r_a, r_ap, n_v);
// printf("\n\t ... back in %d->%d", v, w);
if (r_a[w] >= r_v[v]) {
// printf(" - a[%d] %d >= v[%d] %d", w, r_a[w], v, r_v[v]);
// Articulation point found
r_ap[i] = 1;
}
if (r_a[w] < r_a[v]) {
// printf(" - a[%d] %d < a[%d] %d", w, r_a[w], v, r_a[v]);
r_a[v] = r_a[w];
}
// printf("\n");
}
else {
// printf("back");
// We have already found this vertex before
if (r_v[w] < r_a[v]) {
// printf(" - updating ascent to %d", r_v[w]);
r_a[v] = r_v[w];
}
// printf("\n");
}
}
}
int dfs_art(graph *g, int root, int *r_p, int *r_v, int *r_a, int *r_ap) {
int i, n_visited = 0, n_root_children = 0;
for (i=0; i<g->n_vertices; i++) {
r_p[i] = r_v[i] = r_a[i] = -1;
r_ap[i] = 0;
}
dfs_art_i(g, root, r_p, r_v, r_a, r_ap, &n_visitados);
// the root can only be an AP if it has more than 1 child
for (i=0; i<g->n_vertices; i++) {
if (r_p[i] == root) {
n_root_children ++;
}
}
r_ap[root] = n_root_children > 1 ? 1 : 0;
return 1;
}
If you remove the link between vertices A and B, can't you just check that you can still reach A from B after the edge removal? That's a little better than getting to all nodes from a random node.
How do you choose the edges to be removed?
Can you tell more about your problem domain?
Just how large Is your graph? maybe BFS is just fine!
After you wrote that you are trying to find out whether an edge is a bridge or not, I suggest
you remove edges in decreasing order of their betweenness measure.
Essentially, betweenness is a measure of an edges (or vertices) centrality in a graph.
Edges with higher value of betweenness have greater potential of being a bridge in a graph.
Look it up on the web, the algorithm is called 'Girvan-Newman algorithm'.