PolyBezier equivalent in TBGLVirtualScreen
lazarus / 39-Graphics

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ron.dunn · 2026-01-25 13:04

I'm attempting to make some graphics code faster by moving it from a
standard Canvas to TBGLVirtualScreen's TBGLContext.Canvas.

I've successfully moved lines, rectangles, ellipses and arcs; but I
can't find a functional equivalent for beziers.

Any suggestions?

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Lulu · 2026-01-25 19:30

Hi, I don't know well TBGLVirtualScreen but I think you have already
done the job!
If you see the code in unit BGRACanvasGL, line 1398:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TBGLCustomCanvas.Ellipse(cx, cy, rx, ry: single; AColor:
TBGRAPixel);begin  if AColor.alpha = 0 then exit; 
Polygons(ComputeEllipse(cx,cy,rx,ry),AColor);end;We can see, first an
array of TPointF is returned by ComputeEllipse(...) then this array is
drawn as a consecutive lines by Polygons(array, color).
To render a Bezier curve, first compute its curve with the functions
in unit BGRAPath line 275
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
SplineVertexToSide(y0, y1, y2, y3: single; t: single): single;function
ComputeBezierCurve(const curve: TCubicBezierCurve; AAcceptedDeviation:
single = DefaultDeviation): ArrayOfTPointF; overload;function
ComputeBezierCurve(const curve: TQuadraticBezierCurve;
AAcceptedDeviation: single = DefaultDeviation): ArrayOfTPointF;
overload;function ComputeBezierSpline(const spline: array of
TCubicBezierCurve; AAcceptedDeviation: single = DefaultDeviation):
ArrayOfTPointF; overload;function ComputeBezierSpline(const spline:
array of TQuadraticBezierCurve; AAcceptedDeviation: single =
DefaultDeviation): ArrayOfTPointF; overload;function
ComputeClosedSpline(const APoints: array of TPointF; AStyle:
TSplineStyle; AAcceptedDeviation: single = DefaultDeviation):
ArrayOfTPointF;function ComputeClosedSpline(const APoints: array of
TPointF; AStart, ACount: integer; AStyle: TSplineStyle;
AAcceptedDeviation: single = DefaultDeviation):
ArrayOfTPointF;function ComputeOpenedSpline(const APoints: array of
TPointF; AStyle: TSplineStyle; AEndCoeff: single = 0.25;
AAcceptedDeviation: single = DefaultDeviation):
ArrayOfTPointF;function ComputeOpenedSpline(const APoints: array of
TPointF; AStart, ACount: integer; AStyle: TSplineStyle; AEndCoeff:
single = 0.25; AAcceptedDeviation: single = DefaultDeviation):
ArrayOfTPointF;function ClosedSplineStartPoint(const points: array of
TPointF; Style: TSplineStyle): TPointF;function
ComputeEasyBezier(const curve: TEasyBezierCurve; AAcceptedDeviation:
single = DefaultDeviation): ArrayOfTPointF; then call Polygons()

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ron.dunn · 2026-01-25 23:01

Thank you so much, that pushed me in exactly the right direction.

It all came down to one line of code:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i PolyLines
(ComputeBezierCurve(BezierCurve(p[0],p[1],p[2],p[3])),VGABlack);

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Lulu · 2026-01-26 19:09

Quote from: ron.dunn on January 26, 2026, 12:01:41 amThank you so
much, that pushed me in exactly the right direction.

It all came down to one line of code:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i PolyLines
(ComputeBezierCurve(BezierCurve(p[0],p[1],p[2],p[3])),VGABlack);Happy
to see you have solved your issue.
Regard