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POIs TDirect2DCanvas slow or am I doing something wrong?
 

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  1. POIs TDirect2DCanvas slow or am I doing something wrong?
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    <p>While looking for alternatives to replace GDI, I was trying to test Delphi's 2010 <em>TDirect2DCanvas</em> performance in Windows 7.</p> <p>I tested it by drawing a huge polyline using Direct2D and the result was absurdly slow, even with 500 times less data than the amount I've ran the same test using GDI (and I didn't even use a bitmap as backbuffer in GDI, I just drew to the form canvas directly).</p> <p>So I guess either:<br> <strong>a)</strong> Direct2D is slower than GDI;<br> <strong>b)</strong> TDirect2DCanvas is slow;<br> <strong>c)</strong> I'm doing something wrong<br> and hopefully it's c).</p> <p>The test code I wrote is:</p> <pre><code>unit Unit2; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls, Direct2D, D2D1; type TForm2 = class(TForm) private { Private declarations } FD2DCanvas: TDirect2DCanvas; FData: array[0..50000] of TPoint; public procedure CreateWnd; override; procedure WMSize(var Message: TWMSize); message WM_SIZE; procedure WMPaint(var Message: TWMPaint); message WM_PAINT; { Public declarations } end; var Form2: TForm2; implementation uses utils; {$R *.dfm} procedure TForm2.CreateWnd; var i: Integer; begin inherited; FD2DCanvas := TDirect2DCanvas.Create(Handle); for i := 0 to High(FData) do begin FData[i].X := Random(Self.ClientWidth div 2); FData[i].Y := Random(Self.ClientHeight); end; end; procedure TForm2.WMPaint(var Message: TWMPaint); var PaintStruct: TPaintStruct; begin BeginPaint(Handle, PaintStruct); try FD2DCanvas.BeginDraw; try FD2DCanvas.Polyline(FData); finally FD2DCanvas.EndDraw; end; finally EndPaint(Handle, PaintStruct); end; end; procedure TForm2.WMSize(var Message: TWMSize); begin if Assigned(FD2DCanvas) then begin ID2D1HwndRenderTarget(FD2DCanvas.RenderTarget).Resize(D2D1SizeU(ClientWidth, ClientHeight)); end; end; end. </code></pre> <p>Also, I'm really willing to draw long polylines in real code, as a system I'm working on need to draw plenty of ~2500 points polylines (at least 10K of them).</p> <h2><strong><em>Updated (2010-11-06)</em></strong></h2> <p>I've found out earlier that Direct2D doesn't seem to like polylines, it draws faster if you use a lot of single lines (2 points polylines).</p> <p>Thanks to <a href="https://stackoverflow.com/questions/4055456/is-tdirect2dcanvas-slow-or-am-i-doing-something-wrong/4108046#4108046">Chris Bensen</a> I found out the slowness was with large polylines <em>while using anti-aliasing</em>. So I disabled anti-aliasing as Chris suggested and performance went from ~6000ms to ~3500ms for drawing 50k lines.</p> <p>Things could still be improved because Direct2D just doesn't handle well polylines <em>while using anti-aliasing</em>. With anti-aliasing disabled it's just the opposite.</p> <p>Now the time for drawing with Direct2D the 50k lines, if I draw the large polyline without anti-aliasing, is ~50ms. Nice, eh!</p> <p>The thing is that <strong>GDI is still faster than Direct2D</strong> if I draw to a bitmap and after it's done I BitBlt the result back to the form, it paints <strong>at ~35ms</strong>, and with the same graphics quality. And, Direct2D also seems to be using a backbuffer already (it just draws when <code>EndDraw()</code> is called).</p> <p><strong>So, can this be improved somehow to make using Direct2D worth speed-wise?</strong></p> <p>Here's the updated code:</p> <pre><code>type TArray = array[0..1] of TPoint; PArray = ^TArray; procedure TForm2.WMPaint(var Message: TWMPaint); var PaintStruct: TPaintStruct; begin FD2DCanvas.RenderTarget.SetAntialiasMode(D2D1_ANTIALIAS_MODE_ALIASED); BeginPaint(Handle, PaintStruct); try FD2DCanvas.BeginDraw; try FD2DCanvas.Pen.Color := clRed; FD2DCanvas.Polyline(FData); finally FD2DCanvas.EndDraw; end; finally EndPaint(Handle, PaintStruct); end; end; </code></pre> <p>By the way, even if I use <a href="https://stackoverflow.com/questions/4055456/is-tdirect2dcanvas-slow-or-am-i-doing-something-wrong/4108046#4108046">Chris</a>' suggestion of creating the geometry beforehand the speed is about the same speed as GDI, but still not faster.</p> <p>My computer is running Direct3D and OpenGL apps normally and here's dxDiag output: <a href="http://mydxdiag.pastebin.com/mfagLWnZ" rel="nofollow noreferrer">http://mydxdiag.pastebin.com/mfagLWnZ</a></p> <p>I'll be glad if anyone can explain me why is this slowness. Sample code is much appreciated.</p>
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    1. COTry using a performance profiler. Maybe there's an expensive operation going on behind the scenes that isn't readily apparent.
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    2. COI dont have any answers, but I know you're not the first person to mention that it doesnt seem any faster than GDI.
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