Trouble with Dynamic array implementation

Mike Clark · 2016-12-04T21:01:05

I've been trying to set up a simple method of creating primitives using a simple algorithm, and I need to be able to set the array sizes for the Vertex and Indice lists during runtime using passed parameters. Of course, the simple answer is to use a dynamic array, as opposed to a "compile-time-set" array, My problem is that when I set up and use a dynamic array, I can't seem to get the vertex list into the v_buffer. The compiler doesn't complain, but all I get is an empty world. To test it out, I made a small, simple Vertex/Indice list for a simple triangle. It works just fine if I use a "set-at-compile-time" array, but when I use a dynamic array, I get nothing loaded or displayed. here's the simple code: CUSTOMVERTEX *vertices = new CUSTOMVERTEX[3]; <<=====THIS IS WHAT I NEED TO USE, BUT DOESN'T WORK //CUSTOMVERTEX vertices[3]; <<=====THIS WORKS JUST FINE vertices[0].pos = D3DXVECTOR3(-1.0f, 0.0f, 0.0f); vertices[0].COLOR = RED; vertices[1].pos = D3DXVECTOR3(0.0f, 2.0f, 0.0f); vertices[1].COLOR = GREEN; vertices[2].pos = D3DXVECTOR3(1.0f, 0.0f, 0.0f); vertices[2].COLOR = BLUE; d3ddev->CreateVertexBuffer(3 * sizeof(CUSTOMVERTEX), 0, CUSTOMFVF, D3DPOOL_MANAGED, &v_buffer, NULL); VOID* pVoid; v_buffer->Lock(0, 0, (void**)&pVoid, 0); //memcpy(pVoid, vertices, sizeof(vertices)); <<====THIS WORKS JUST FINE WITH A FIXED-AT-COMPILE ARRAY v_buffer->Unlock(); short indices[] = { 0,1,2, }; d3ddev->CreateIndexBuffer(3 * sizeof(short), 0, D3DFMT_INDEX16, D3DPOOL_MANAGED, &i_buffer, NULL); i_buffer->Lock(0, 0, (void**)&pVoid, 0); memcpy(pVoid, indices, sizeof(indices)); i_buffer->Unlock(); vertices = nullptr; delete[] vertices; I Know that "new" variables pass a pointer, so I think that it's a simple error on my part in the code for loading the v_buffer, but I can't figure this out. Any help aould be very much appreciated. Cheers!

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Started by pharoah0110 December 02, 2016 08:09 PM

10 comments, last by Khatharr 8 years ago

SeanMiddleditch

17,596

December 04, 2016 07:50 AM

Ok, finally got the Vector thing figured out. You were right about not using "at()", simply replacing every occurrence of it with "vertices[n]" did the trick, and it's working fine now.

That mildly surprises me, but I'm not intimately familiar with the semantics of .at() since I have never once used it in 20 years. :)

works quite well. Despite that, is there a reason I should use another format? Just asking because you said not to use the "&vertices[0]" idiom. Not quite sure what you meant by that. Removing the ampersand, or the "[0]" reference causes a crash.

Like I said, use .data() instead. Replace &indices[0] with indices.data()

Regarding this, I think EASTL had a member function for getting the byte length of a vector. Are you aware of any talk about upgrades to std::vector along these lines? I was disappointed recently to find that there doesn't appear to be a standard way to refer to a vector's type that works with sizeof(). I was thinking that sizeof(vec.value_type) was possible until I tried it.

I have an extremely vague recollection of it being discussed on the main isocpp reflector a while ago, but I don't recall an actual paper being submitted.

Quite possibly worth bringing up on the c++ sg14 reflector. *nudge* :)

Sean Middleditch – Game Systems Engineer – Join my team!

Khatharr

8,814

December 04, 2016 09:01 PM

I'm about to be conscripted for some housework, but I'll see what I can do later. I was looking at it yesterday and apparently there's a workaround at present in the form of sizeof(decltype(vec)::value_type), so in theory it shouldn't be too difficult to work out something more convenient.

Edit: Posted.

void hurrrrrrrr() {__asm sub [ebp+4],5;}

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