I'm still unsure.

- If I want to simulate fire flames rising should I animate the UV?

- If yes, how? I tried to use the code provided by "belfegor" but can't get it to work.

BTW, the way I set the UV to make the entire texture appear is as the following:

vertices[j*4+0] = CUSTOM_VERTEX(pos, color, 0.0f, 0.0f);
vertices[j*4+1] = CUSTOM_VERTEX(pos, color, 0.0f, 1.0f);
vertices[j*4+2] = CUSTOM_VERTEX(pos, color, 1.0f, 1.0f);
vertices[j*4+3] = CUSTOM_VERTEX(pos, color, 1.0f, 0.0f);

If I want to simulate fire flames rising should I animate the UV?

There is no one and only way to simulate something. It depends how YOU want to do it.

I tried to use the code provided by "belfegor" but can't get it to work.

What have you tried and failed? Show some code, don't just say "i can't get it to work". How do you expect someone to help you with no relative information?

Put this somewhere at "init time"

const int framesCnt = 16;

const float uvOffset = 1.0f / (float)framesCnt;

D3DXVECTOR2 billUV[4];

billUV[0].x = 0; // top left

billUV[1].x = 0; // bottom left

billUV[2].x = uvOffset; // top right

billUV[3].x = uvOffset; // bottom right

 

billUV[0].y = 0; // top left

billUV[1].y = 1; // bottom left

billUV[2].y = 1; // bottom right

billUV[3].y = 0; // top right

Do this every frame, might be where you update your vertices

static float time = 0.0f;

const float animSpeed = 1.0f / 30.0f; // 30 frames per second

time += deltaTime;

if( time > animSpeed)

{

    time = 0.0f;

    billUV[0].x += uvOffset;

    billUV[1].x += uvOffset;

    billUV[2].x += uvOffset;

    billUV[3].x += uvOffset;

 

    if( billUV[3].x > 1.0f )  // reset to beginning

    {

        billUV[0].x = 0; // top left

        billUV[1].x = 0; // bottom left

        billUV[2].x = uvOffset; // top right

        billUV[3].x = uvOffset; // bottom right

    }

}

Then set to your vertices

vertices[j*4+0] = CUSTOM_VERTEX(pos, color, billUV[0].x, billUV[0].y);

vertices[j*4+1] = CUSTOM_VERTEX(pos, color, billUV[1].x, billUV[1].y);

vertices[j*4+2] = CUSTOM_VERTEX(pos, color, billUV[2].x, billUV[2].y);

vertices[j*4+3] = CUSTOM_VERTEX(pos, color, billUV[3].x, billUV[3].y);

Look for example texture in attachment.