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  Basic proof of PO2 size  (Read 826 times)
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Offline K.I.L.E.R

Senior Member




Java games rock!


« Posted 2006-11-10 11:46:22 »

I know the solution is simple to calculate, I just dislike the current solution because of lack of proof behind it(who gives a damn if it works? It has to be proven in the realm of mathematics before it's useful).
I had to revisit this issue because I have to make a 3D networked game for my assignment and wanted to re-invent the wheel, with solid proof.

If you don't care about this then don't read it. I only did this as a proof for my assignment and thought maybe someone might benefit from my proof.

lambda = texture dimension size (either width or height)
alpha = some unknown integer value that is the power

This statement is assuming that the current dimension is PO2 but since I don't know this, I thought I'd try and find the power while converting the base from PO2 into something more common (base e).
lambda = 2^alpha

Convert base 2 to base e.

ln(lambda) = ln(2^alpha)
ln(lambda) = alpha*ln(2)

alpha = ln(lambda) / ln(2)

How to get this to work?

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private static boolean isPowerOf2(final int width, final int height) {
   currentImageScaledWidth = (int) Math.pow(2, Math.ceil(Math.log(width) / Math.log(2)));
   currentImageScaledHeight = (int) Math.pow(2, Math.ceil(Math.log(height) / Math.log(2)));
   return ((width == currentImageScaledWidth) && (height == currentImageScaledHeight));
}


If it's already a PO2 texture then nothing happens. If a dimension isn't PO2, then it converts to the nearest higher PO2 dimension.

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Texture tex = TextureLoader.load("C:\\Documents and Settings\\Kruno\\Desktop\\newOOP2Ass\\res\\Title.BMP");
double curTexBaseX = Math.log(tex.width) / Math.log(2);
double curTexBaseY = Math.log(tex.height) / Math.log(2);
         
System.out.println(tex);
System.out.print("PO2 Width: " + Math.pow(2, Math.ceil(curTexBaseX)));
System.out.print("\t PO2 Height: " + Math.pow(2, Math.ceil(curTexBaseY)));


Quote
Output:
BPP: 3     Width: 453     Height: 239     Scaled Width: 512     Scaled Height: 256
PO2 Width: 512.0    PO2 Height: 256.0

Vorax:
Is there a name for a "redneck" programmer?

Jeff:
Unemployed. Wink
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