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CHTHONIC

ID3DXFont::DrawText

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A question regarding the ID3DXFont interface. First off just so that you do not have to look it up here is the prototype for the method: INT DrawText( LPD3DXSPRITE pSprite, LPCTSTR pString, INT Count, LPRECT pRect, DWORD Format, D3DCOLOR Color ); The first parameter is optional but according to "google" it can speed up the method by 4 or 5 times. However I am a little lost as to what exactly you are providing for this performance boost. I have trawled through the net (via google) for a basic example of this being demonstrated but have had no luck. I was wondering if anyone else knew of one or could at least point me in the right direction. Thanks a lot, Alex.

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Quote:
Original post by CHTHONIC
The first parameter is optional but according to "google" it can speed up the method by 4 or 5 times. However I am a little lost as to what exactly you are providing for this performance boost. I have trawled through the net (via google) for a basic example of this being demonstrated but have had no luck. I was wondering if anyone else knew of one or could at least point me in the right direction.

When you don't specify your own sprite object, ID3DXFont must use it's own internal one. And each time you draw text, it does something like the following:
sprite->Begin()
draw text
sprite->End()

Notice that for each string you draw, it must flush the sprite, which is expensive. This is what would happen if you specified your own sprite:
sprite->Begin()  // You would call this on your own
fontA->DrawText() // All of your text drawing
fontA->DrawText()
fontB->DrawText()
fontC->DrawText()
...
sprite->End()

Now, you only have one batch of sprites, which is far more efficient. Note that simply adding a Begin()/End() pair to font wouldn't fix the issue, since you are most likely going to be drawing with multiple fonts.

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Thanks CircleSoft,

Yes that makes perfect sense. However, I am still a little confused. Are you saying i just pass in a pointer to the ID3DXSPRITE interface I am using to render other sprites or do i need to do something to it before i pass it in? The documentation on the net is awful for this!

Thanks a lot,

Alex.

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Hey again,

It does not like it if i just pass in a pointer to my sprite interface. It works if i pass in null but it really is awfully slow. Any ideas? (sorry if this is obvious, i just do not get the point at all).

Thanks for your time,

Alex.

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Quote:
Original post by CHTHONIC
Hey again,

It does not like it if i just pass in a pointer to my sprite interface. It works if i pass in null but it really is awfully slow. Any ideas? (sorry if this is obvious, i just do not get the point at all).

Thanks for your time,

Alex.


As circlesoft already mentioned, you need to call ID3DXSprite::Begin() with D3DXSPRITE_ALPHABLEND in the parameter before drawing text. (And again as circlesoft mentioned you need to call ID3DXSprite::End() once you're done drawing text.

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