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dynamic polygon creation?

Started by argonaut Mar 31, 2007 at 9:38 PM 1 replies 650+ views

Original Post

Mar 31, 2007 at 9:38 PM

I'm trying to dynamically allocate some polys, but I haven't been able to figure out how just yet. This code is in my render loop, so far. Here is my code:


	static int startCount = GetTickCount();
	static float cx = 0;
	// calculate the size of the new vertex 
	int objCount = 1 + (GetTickCount() - startCount) / 1000;
	// create a new vertex data set
	stD3DVertex *objData = new stD3DVertex[objCount];
	// loop through to create the new vertex data set
	for(int i = 0; i < objCount; i++)
	{
		cx = i + 0.5f - (float)(rand() % 1000) / 1000.0f;
		// objectargs must be delivered independently

		stD3DVertex objArg[] = {   {-2.5f - cx, -0.5f, -6.0f, D3DCOLOR_ARGB(255,255,255,255), 0.0f, 1.0f},
			{2.5f, -0.5f,  -6.0f, D3DCOLOR_ARGB(255,255,255,255), 1.0f, 1.0f},
			{2.5f, -0.5f, 6.0f, D3DCOLOR_ARGB(255,255,255,255), 1.0f, 0.0f},

			{2.5f, -0.5f, 6.0f, D3DCOLOR_ARGB(100,255,255,255), 1.0f, 0.0f},
			{-2.5f - cx, -0.5f, 6.0f, D3DCOLOR_ARGB(100,255,255,255), 0.0f, 0.0f},
			{-2.5f - cx, -0.5f, -6.0f, D3DCOLOR_ARGB(100,255,255,255), 0.0f, 1.0f}
		};
	// deliver the data set to the vertex buffer
	objData = *objArg;
	}
   // Create the vertex buffer.
   if(FAILED(g_D3DDevice->CreateVertexBuffer(sizeof(objData), 0,
             D3DFVF_VERTEX, D3DPOOL_DEFAULT,
             &g_VertexBuffer, NULL))) return;
   
   // Fill the vertex buffer.
   void *ptr;
   if(FAILED(g_VertexBuffer->Lock(0, sizeof(objData),
      (void**)&ptr, 0))) return ;
   memcpy(ptr, objData, sizeof(objData));

   g_VertexBuffer->Unlock();

The problem lies in sending the objArg pointer to the objData array. Wow, I'm sure i'm going to get flamed for this, but salvo away!! [Edited by - argonaut on March 31, 2007 10:54:31 PM]

Mastaba

Apr 1, 2007 at 2:26 AM

I see a couple of errors, both semantic. One is, you allocate an array of objcount stD3DVertex objects, then for in the loop, from 0 to objcount , you create six that you want to copy to the array (thus your array needs to allocate space for 6*objcount stD3DVertex objects). Next why not simply create the objects in the vertex array to begin with rather than to a temporary array that that you then copy to the other array?

Something like this:

static float cx = 0;	// calculate the size of the new vertex 	int objCount = 1 + (GetTickCount() - startCount) / 1000;  // Create the vertex buffer.   if(FAILED(g_D3DDevice->CreateVertexBuffer(6*objCount*sizeof(stD3DVertex), 0,             D3DFVF_VERTEX, D3DPOOL_DEFAULT,             &g_VertexBuffer, NULL))) return;      // Fill the vertex buffer.   stD3DVertex *vertex;   if(FAILED(g_VertexBuffer->Lock(0, 0,      (void**)&vertex, 0))) return ;	// loop through to create the new vertex data set	for(int i = 0; i < objCount; i++)	{		cx = i + 0.5f - (float)(rand() % 1000) / 1000.0f;		// objectargs must be delivered independently		*vertex++ = stD3DVertex(-2.5f - cx, -0.5f, -6.0f, D3DCOLOR_ARGB(255,255,255,255), 0.0f, 1.0f);		*vertex++ = stD3DVertex(2.5f, -0.5f,  -6.0f, D3DCOLOR_ARGB(255,255,255,255), 1.0f, 1.0f);		*vertex++ = stD3DVertex(2.5f, -0.5f, 6.0f, D3DCOLOR_ARGB(255,255,255,255), 1.0f, 0.0f);		*vertex++ = stD3DVertex(2.5f, -0.5f, 6.0f, D3DCOLOR_ARGB(100,255,255,255), 1.0f, 0.0f);		*vertex++ = stD3DVertex(-2.5f - cx, -0.5f, 6.0f, D3DCOLOR_ARGB(100,255,255,255), 0.0f, 0.0f);		*vertex++ = stD3DVertex(-2.5f - cx, -0.5f, -6.0f, D3DCOLOR_ARGB(100,255,255,255), 0.0f, 1.0f);	}    g_VertexBuffer->Unlock();

Though you'll need the relevant stD3DVertex constructor, which I assume is available. Also sizeof objData is always the size of a pointer, not the array it points to since it is defined as a pointer rather than an array. You also have a potential memory leak in the code but I'm assuming this is just for illustrative purposes and not actual code so I'll overlook that.

argonaut

Apr 1, 2007 at 2:34 AM

Wow! Interesting technique. I'll have to give it a try! Thanks for the response :)

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