Direct3D polygon with C++ 2010

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I am a beginner using Direct3D C++ 2010. Trying to build Tutorial2 which shows 3 vertices for a triangle.
Works fine.
Now I need to understand how to display many triangles.
Based on suggestions from Jack Dingler,
I changed the vertices to 2 triangles as below.
Also changed the buffer parameter 3 * to 6*.
Currently it displays only the first triangle.
Which call below has the number of triangles to display?
Please help.
thanks
ayyangar
6/21

C++

CUSTOMVERTEX vertices[] =
  {
    { 250.0f,  50.0f, 0.5f, 1.0f, 0xffff0000, }, // x, y, z, rhw, color
      { 250.0f, 250.0f, 0.5f, 1.0f, 0xffff0000, },
      { 50.0f, 250.0f, 0.5f, 1.0f, 0xfffffffff, },
      { 50.0f, 250.0f, 0.5f, 1.0f, 0xfffffffff, },
      { 50.0f, 50.0f, 0.5f, 1.0f, 0xfffffffff, },
      { 250.0f,  50.0f, 0.5f, 1.0f, 0xffff0000, },
  };

if( FAILED( g_pd3dDevice->CreateVertexBuffer( 6 * sizeof( CUSTOMVERTEX ),
                                               0, D3DFVF_CUSTOMVERTEX,
                                               D3DPOOL_DEFAULT, &g_pVB, NULL ) ) )
 {
     return E_FAIL;
 }

//part of the code from Render is given below.

VOID Render()

g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof( CUSTOMVERTEX ) );
   g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
   g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLELIST, 1, 1 );

Posted 20-Jun-12 5:38am

ayyangar

Updated 21-Jun-12 9:17am

Sandeep Mewara

v3

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JackDingler 20-Jun-12 13:11pm

What doesn't work? Does the CreateVertexBuffer call fail?

If so, what error does it return?

From MSDN:

Return value

Type: HRESULT

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be one of the following: D3DERR_INVALIDCALL, D3DERR_OUTOFVIDEOMEMORY, E_OUTOFMEMORY.

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JackDingler · Answer 1 · 2012-06-20T07:53:00

Solution 2

Are you calling code to draw triangles or quads?

If you're calling a function to draw a triangle, it will only use sets of 3 vertices. If you want to use a triangle drawing function to draw a polygon, you'll need to divide it into a mesh of triangles.

To draw a four sided polygon, you'll need 2 triangles.

Keep in mind that triangles have a facing order.

The order that you provide vertices in, determines which face is the front and which is the back.

Posted 20-Jun-12 7:53am

JackDingler

Updated 20-Jun-12 7:54am

v2

Comments

ayyangar 20-Jun-12 14:27pm

thanks. now i understand that i need to draw 2 triangles. how do i setup the code. i made 6 vertices all together. now it crashes, it would be better if you send me the code to setup the vertices
CUSTOMVERTEX vertices[] =
{
{ 250.0f, 50.0f, 0.5f, 1.0f, 0xffff0000, }, // x, y, z, rhw, color
{ 250.0f, 250.0f, 0.5f, 1.0f, 0xffff0000, },
{ 50.0f, 250.0f, 0.5f, 1.0f, 0xfffffffff, },
{ 50.0f, 250.0f, 0.5f, 1.0f, 0xfffffffff, },
{ 50.0f, 50.0f, 0.5f, 1.0f, 0xfffffffff, },
{ 250.0f, 50.0f, 0.5f, 1.0f, 0xffff0000, },
};

JackDingler 20-Jun-12 14:51pm

At what line does it crash? What function is being called when it crashes?

ayyangar 20-Jun-12 15:09pm

It crashed because of CreateVertexBuffer(3* . it does not crash with value 6
however, it only displays the first triangle.

JackDingler 20-Jun-12 15:18pm

Please use the "Improve Question" button to provide information on what function you're passing the buffer to, to do the drawing with.

The CreateVertexBuffer function doesn't actually do the drawing. the value of 6 looks correct. Somewhere else, you make a call to display the triangle and you're telling it that it should draw just one triangle. We need to identify that call, and let it know that you're drawing two triangles.

ayyangar 20-Jun-12 17:28pm

Where do i find the "Improve Question" button? Is it a part of the Visual Studio ?

JackDingler 21-Jun-12 0:19am

Scroll up.... :)

JackDingler 23-Jun-12 14:49pm

It would be a good idea to read the documentation for each method called in your program. You might not understand right away what their purpose is, but over time, as you learn more and more, you'll catch on.

I can see that it's not clear to you where the drawing actually happens. You posted code with the method SetStreamSource() added. But that doesn't actually output the triangles either.

The sort of function I was hoping I could get you to examine, might have a call to DrawTriPatch(). Note that there is also a function for DrawRectPatch() which takes four vertices for each mesh item.