Algorithm in Java

[MaxPower]

Can anyone help me I am stumped, I want to convert this algorithm into Java any var names will do:



I have either got it right and its not working or I haven't got it right so I would like to eliminate one of these.

Anyone brave enough?

 

[matja]

i_a = (1/(y_1-y_2))*((i_1*(y_s-y_2))+(i_2*(y_1-y_s)));

 

[MaxPower]

i_a = (1/(y_1-y_2))*((i_1*(y_s-y_2))+(i_2*(y_1-y_s)));

Yup Identical to what I had, but it doesn't seem to work, clearly it must be one of my parameters.

Many thanks for your help.

 

[drak3]

This is recursive I think

what Ia and Ys stand for?

 

[triggerthat]

What does the algorithm do? Google it prehaps?

 

[Una]

Make sure you are using the correct data types (Prolly doubles).

 

[Dj_Jestar]

I'm utterly hopeless at mathematics, to the point where that formula might as well be a random scribble, but perhaps the number is out of range of a 32bit based system like Java?

 

[MaxPower]

Yes it is recursive, it is an algorithm for gouraud shading to calculate the intensity of a colour (i_a) on a line given the y coordinate of both points on the line (y_1 & y_2), the intensity at both these points (i_1 & i_2) and the current scanline (y_s).

The reason I believe it is not working is that the output should logically be a value between i_1 and i_2 however putting a print statement after the algorithm displays that even if the values are:

i_1 = 200 and i_1 = 255

The result is still i_a = 871

Some of the lines work its odd.

 

[matja]

Works fine for me :

y_1 = 100; i_1 = 200;
y_2 = 200; i_2 = 255;
y_s = 150;
i_a = (1/(y_1-y_2))*((i_1*(y_s-y_2))+(i_2*(y_1-y_s)));

i_a is 227.5 - half way between 200 and 255, as expected.

Are you using floats?

 

[MaxPower]

Works fine for me :

y_1 = 100; i_1 = 200;
y_2 = 200; i_2 = 255;
y_s = 150;
i_a = (1/(y_1-y_2))*((i_1*(y_s-y_2))+(i_2*(y_1-y_s)));

i_a is 227.5 - half way between 200 and 255, as expected.

Are you using floats?

I think Ive got it, I my y_s wasn't between y_1 and y_2;

Thanks for your help. I may need more help yet.