Thread: help on algorithm (HUD BAR)

Hello I am trying to draw a bar which has curves on its either side but the curves are seem imperfect. Can anyone help me on the following code?




barValue gives the amount of value the bar should have with respect to the width.
the Bar should not be drawn fully but upto the value of barValue.
The posinfo contains the coordinates of the line to be drawn.
The drawTexture draws on to the screen take the line texture address, posinfo address and color addres.

Code:

define LINE_WIDTH 0.5f


void drawHUDBar(int texNum,float X,float Y,float width,float height,float barValue)
{
	float newYScale=0.0f;
	float radius=height/2.0f;
	float l;
	for ( l=0.0f;l<=barValue;l=l+LINE_WIDTH)
	{
  if (l<=radius)
  {
  	newYScale=sqrtf(radius*radius-(radius-l)*(radius-l));
  	posInfo.x1=X+l;
  	posInfo.y1=Y+radius-newYScale;
  	posInfo.x2=posInfo.x1+LINE_WIDTH;
  	posInfo.y2=Y+radius+newYScale;
  	drawTexture(&texturePtr,&posInfo,&default_color);
  }
  else if (l<(width-radius))
  {
  	posInfo.x1=X+radius;
  	posInfo.y1=Y;
  	if (barValue<=(width-radius)) posInfo.x2=posInfo.x1+barValue-radius;
  	else posInfo.x2=posInfo.x1+width-2*radius;
  	posInfo.y2=Y+2*radius;
  	drawTexture(&texturePtr,&posInfo,&default_color);
  	l=width-radius-LINE_WIDTH;
  }
  else if (l>=(width-radius))
  {
  	newYScale=sqrtf(radius*radius-(radius-width+l)*(radius-width+l));
  	posInfo.x1=X+l;
  	posInfo.y1=Y+radius-newYScale;
  	posInfo.x2=posInfo.x1+LINE_WIDTH;
  	posInfo.y2=Y+radius+newYScale;
  	drawTexture(&texturePtr,&posInfo,&default_color);
  }
  
	}
}

If there is better or faster algorithm please do post

Why don't you just use a bitmap of the curve and then interpolate across the bitmap to show different portions of it? With some alpha blending you can achieve some pretty cool effects like this all the while using textures. The upside to this is that it is much simpler to use textures for this than vector graphics or some other approach.

They seem to be fine when the height is increased but if the height is small if is kind of imperfect.
I have modified them to work properly with every resolutions by putting a resolution multiplier.
http://img638.imageshack.us/img638/307/82086393.jpg

Code:

int round2int(float f)
{
   int a;


   a=(int)f;
   if(f-a>0.5)return a+1;
   if(f-a<-0.5)return a-1;
   return a;
}


void HUDstyle_1(int texNum,float X,float Y,float width,float height,float barValue)
{
	float newYScale=0.0f;
	float radius=height/2.0f;
	float l;
	for ( l=0.0f;l<=barValue;l=l+LINE_WIDTH)
	{
		if (l<=radius)
		{
			newYScale=round2int(sqrtf(radius*radius-(radius-l)*(radius-l)));
			posInfo.x=X+l;
			posInfo.y=Y+radius-newYScale;
			posInfo.w=posInfo.x+LINE_WIDTH;
			posInfo.h=Y+radius+newYScale;
			drawTexture(&texturePtr,&posInfo,&default_color);
		}
		else if (l<(width-radius))
		{
			posInfo.x=X+radius;
			posInfo.y=Y;
			if (barValue<=(width-radius)) posInfo.w=posInfo.x+barValue-radius;
			else posInfo.w=posInfo.x+width-2*radius;
			posInfo.h=Y+2*radius;
			drawTexture(&texturePtr,&posInfo,&default_color);
			l=width-radius-LINE_WIDTH;
		}
		else if (l>=(width-radius))
		{
			newYScale=round2int(sqrtf(radius*radius-(radius-width+l)*(radius-width+l)));
			posInfo.x=X+l;
			posInfo.y=Y+radius-newYScale;
			posInfo.w=posInfo.x+LINE_WIDTH;
			posInfo.h=Y+radius+newYScale;
			drawTexture(&texturePtr,&posInfo,&default_color);
		}
		
	}
}

I am now using this function and thank you the symmetry is now perfect but still the curve is not as it should be.

Ok now I see what you are trying to do and there is a much simpler way. Go to Blender and create a model 1 unit by 1 unit that is the bar you want. Now load that and render it on your screen after doing the standard SRT transformations. If you want to do this manually your model is a rectangle surrounded on either side by 2 triangle fans. That would be a much simpler way to render this.

Indeed. That is what I was referring to when I mentioned the alpha blending. The same tricks can be applied to draw round controls and mini-maps on your screen. Just alpha out the portions that you do not want to see.