Octopus Tentacles: Bgrabmp ellipse too slow but GL does it
lazarus / 39-Graphics

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Boleeman · 2025-07-29 09:42

Hi all.

I tried making an octopus tentacles animation but I am finding the
movement of the tentacles very sluggish.

The alpha changes as the tentacles sway.

Not sure how to improve the speed of the tentacles movement to make a
hypnotic movement?

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Gigatron · 2025-07-29 14:03

Quote from: Boleeman on July 29, 2025, 11:42:31 amHi all.

I tried making an octopus tentacles animation but I am finding the
movement of the tentacles very sluggish.

The alpha changes as the tentacles sway.

Not sure how to improve the speed of the tentacles movement to make a
hypnotic movement?

Nice @Boleeman

To test the glCanvas quick conversion to gl version of this cool fx;

Regards

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Thaddy · 2025-07-30 07:37

Nice!
Nice conversion to glcanvas too...

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Boleeman · 2025-07-30 13:29

Wow GigaTron.

Looks like GL is the way to go for Ellipse animations.
That's the exact effect that I was trying to achieve.

For some reasonTBgrabmp does not handle ellipse animations well, but
its really good at stationary renders.

Thanks Gigatron.

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Boleeman · 2025-07-30 13:52

Actually Gigtron, not sure if you could possibly help with another
ellipse animation?

I had another project of a Burning sun that uses ellipses, but it also
has Canvas2D to do ctx.Translate(x, y);
Not sure if you could possibly work out how to do it in GL?

The effect should be a really nice trippy burning Sun, but I could not
get this to animate properly.

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Gigatron · 2025-07-30 15:16

Quote from: Boleeman on July 30, 2025, 03:52:04 pmActually Gigtron,
not sure if you could possibly help with another ellipse animation?

I had another project of a Burning sun that uses ellipses, but it also
has Canvas2D to do ctx.Translate(x, y);
Not sure if you could possibly work out how to do it in GL?

The effect should be a really nice trippy burning Sun, but I could not
get this to animate properly.

Hi, i have not all gl functions to translate rotate like ctx Canvas2D;
but this conversion is not bad i think;

Regards

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Gigatron · 2025-07-31 00:50

Hi

With the new version of the glcanvas  the code is more understandable
and easy,
support of ctx.save, ctx.restore, ctx.translate, ctx.rotate + 3D cubes
;

glSaveMatrix;
glRestoreMatrix;
glTranslateMatrix(rayX, rayY, 0);
glRotateMatrix(-i + rot, 0, 0, 1); // Z rotation  

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 unit
Unit1; {$mode objfpc}{$H+} interface uses  Classes, SysUtils, Forms,
Controls, Graphics, Dialogs, ExtCtrls,  OpenGLContext, Math,
glcanvas; type  { TForm1 }  TForm1 = class(TForm)    OpenGLControl1:
TOpenGLControl;    Panel1: TPanel;    Timer1: TTimer;    procedure
FormCreate(Sender: TObject);    procedure OpenGLControl1Paint(Sender:
TObject);    procedure Timer1Timer(Sender: TObject);  private    num,
rot: Single;  public  end; var  Form1: TForm1; implementation {$R
*.lfm} { TForm1 } procedure TForm1.Timer1Timer(Sender: TObject);begin 
OpenGLControl1.Invalidate;end; procedure TForm1.FormCreate(Sender:
TObject);begin  glInit(OpenGLControl1);  if not
OpenGLControl1.MakeCurrent then raise Exception.Create('OpenGL context
makeCurrent Error');  num := 0;  rot := 0;end; procedure
TForm1.OpenGLControl1Paint(Sender: TObject);var  i, q: Integer;  a, d:
Single;  cx, cy: Integer;  rayX, rayY: Single;begin  if not
OpenGLControl1.MakeCurrent then Exit;  glFillScreen(OpenGLControl1,
0.0, 0.0, 0.0, 1.0);   cx := OpenGLControl1.Width div 2;  cy :=
OpenGLControl1.Height div 2;   glSaveMatrix;                    //
sun  glTranslateMatrix(cx, cy, 0);   for i := -180 to 179 do    if i
mod 12 = 0 then    begin      rayX := sin(DegToRad(i)) * 15;      rayY
:= cos(DegToRad(i)) * 15;       glSaveMatrix;     
glTranslateMatrix(rayX, rayY, 0);      glRotateMatrix(-i + rot, 0, 0,
1); // Z rotation       for q := 0 to 195 do        if q mod 5 = 0
then        begin          d := 40 - (q / 200) * 40;          a :=
sin(DegToRad(-i + q + num)) * 2;          glEllipse(a, q * 1.7, d, d,
20, 1.0, 0.6, 0.0, 0.1, true);        end;       glRestoreMatrix;  
 // rays    end;   glRestoreMatrix;  // sun  glSaveMatrix; 
glFilled3DCube(OpenGLControl1, -80, 0, 0,  50, 1.0, 1.0, 1.0, 1.0,
rot, -rot, rot, 0.0, 0.0, 1.0);  glWired3DCube(OpenGLControl1,  -80,
0, 0,  50, 1.0,0.0,0.0, 1.0, rot, -rot, rot, 4.0);  glRestoreMatrix; 
glFilled3DCube(OpenGLControl1, 80, 0, 0, 50, 0.0,0.5,1.0, 1.0, rot,
rot, rot, 1.0, 0.0, 0.0);  glWired3DCube(OpenGLControl1, 80, 0, 0,
 50, 0.5,0.5,0.5, 1.0, rot, rot, rot, 4.0);  num += 11.5;  // deg  rot
+= 1.15;  // deg   OpenGLControl1.SwapBuffers;end; end.

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Boleeman · 2025-07-31 08:56

Thanks for helping out Gigatron.


I used a := sin(DegToRad(-i + q + num)) * 10; to make the rendering
wobble a bit more.
Now need to try to make an alpha trail from the vertices to make it
look like heat is coming from it, like a heat trail from the Sun.

I will need to learn a bit more about GL from your latest code.

Wondered if GL also does conic gradient? as TBgrabmp only has linear
and radial gradient.

Thanks Gigatron for your help.