6 replies to this topic

[phil67rpg]

I am studying the directx9tutorial.com web site.one of their exercises is to change the shape of a triangle during runtime. Here is some of the code given from this tutorial.

// this is the function used to render a single frame
void render_frame(void)
{
    d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);

    d3ddev->BeginScene();

        // select which vertex format we are using
        d3ddev->SetFVF(CUSTOMFVF);

        // select the vertex buffer to display
        d3ddev->SetStreamSource(0, v_buffer, 0, sizeof(CUSTOMVERTEX));

        // copy the vertex buffer to the back buffer
        d3ddev->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 1);

    d3ddev->EndScene();

    d3ddev->Present(NULL, NULL, NULL, NULL);
}


// this is the function that cleans up Direct3D and COM
void cleanD3D(void)
{
    v_buffer->Release();    // close and release the vertex buffer
    d3ddev->Release();    // close and release the 3D device
    d3d->Release();    // close and release Direct3D
}


// this is the function that puts the 3D models into video RAM
void init_graphics(void)
{
    // create the vertices using the CUSTOMVERTEX struct
    CUSTOMVERTEX vertices[] =
    {
        { 400.0f, 62.5f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255), },
        { 650.0f, 500.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 255, 0), },
        { 150.0f, 500.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0), },
    };

    // create a vertex buffer interface called v_buffer
    d3ddev->CreateVertexBuffer(3*sizeof(CUSTOMVERTEX),
                               0,
                               CUSTOMFVF,
                               D3DPOOL_MANAGED,
                               &v_buffer,
                               NULL);

    VOID* pVoid;    // a void pointer

    // lock v_buffer and load the vertices into it
    v_buffer->Lock(0, 0, (void**)&pVoid, 0);
    memcpy(pVoid, vertices, sizeof(vertices));
    v_buffer->Unlock();

[Postie]

Nice code, but did you have a question?

[phil67rpg]

yes I have drawn a triangle but I want to change it to a square during runtime.

[Morphex]

Just few tips, a triangle has 3 vertices a square has 4 at least (you may need more).

Find where you declare vertices,

 

You will need a switch to check if you are in square mode or triangle mode, and to a way to change that switch at runtime. (By switch I mean a Bool variable, True, False)

[Khatharr]

Phil got the code tags working! +1!

Let us know how it turns out, bud.

[Endurion]

Just few tips, a triangle has 3 vertices a square has 4 at least (you may need more).

Find where you declare vertices,

 

You will need a switch to check if you are in square mode or triangle mode, and to a way to change that switch at runtime. (By switch I mean a Bool variable, True, False)

There is no square mode.

 

A square is simply a list of two triangles instead of 1. The simplest way would be to add the 3 vertices of the second triangle to your vertex array , change the "3*" in the CreateVertexBuffer call to "6*" and change the "1" in the DrawPrimitive call to "2".

Get that working first, don't bother with the other primitive types yet.

[phil67rpg]

thanks a lot I got it working also thanks for the rep points