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Well it is. 
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Computafreak wrote: Multiply out the brackets:
0.75*N*N^2 = A
No, you started out with wrong equation.
Shouldn't it be
A = h * w
A = N * .75N
A = .75 * N^2
A/.75 = N^2
N = sqrt(A/.75)
we know A = 480000
N = sqrt(480000/.75 )
N = sqrt(360000 640000)
N = 600 800
[edit] modified calculation error, thanks Computafreak[/edit]
Yusuf
modified on Sunday, March 8, 2009 7:53 AM
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My bad; I misread the equation. I've edited my post. Either way, I didn't think that 480000/0.75 was equal to 36000. Did you accidentally multiply?
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Computafreak wrote: I didn't think that 480000/0.75
my bad, a bug in my calculation. 
480000/0.75 = 640000
Yusuf
Oh didn't you notice, analogous to square roots, they recently introduced rectangular, circular, and diamond roots to determine the size of the corresponding shapes when given the area. Luc Pattyn[^]
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Sorry for the delay in responding. You have enough information to solve this. You have two equations and two unknowns. We know the area and the width to height ratio.
So:
1.) width * height = area
2.) height = 0.75 * width
so, substituting (2) into (1)
0.75 * width * width = area
Rearranging:
3.) width = sqrt(area/0.75)
Using your numbers as an example:
width = sqrt(480000/0.75) = 800
then putting this into the height constraint:
height = 0.75 * width = 0.75 * 800 = 600
So for the 480,000 example, width should be 800, height 600. So, just solve equation (3) for the width and then plug the width result into (2) to get the height.
modified on Saturday, March 14, 2009 8:31 AM
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Zeppelin, thank you. Just like Led Zeppelin, top of your field.
I would have never got there, but once i see it i completly understand it.
Cheers
Cloughy
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No problem. It's what this forum is for.
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Do you know a free Computer Graphics library complex and wide enough to make advanced artistic Computer Graphic effects?
Since it's hard to explain exactly what I'm talking about, here you can see the kind of thing I'm would like to be able to make: www.picturetopeople.org[^]. There they say it's all been made absolutely from scratch, but I'm afraid their CG libraries are not open source.
Some photo effects you can see in this address are well explained in CG text books, like the dithering, mosaic and warping ones, but there are many effects there I have never seen in books, like pencil, drawing, painting and sketch.
About text and pattern effects, maybe it's even harder. They look like drawing with very complex procedural brushes matching directional fields or so. I couldn't find advanced enough explanations to achieve that result level.
Is there any CG library able to make all of that?
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You could take a look at the Paint.Net source code.
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I already made it. paint.net is too much simple. It has just the trivial.
I had a look at gimp source. It's much better than paint.net, but it's still far from what I want.
I'm afraid there is no so advanced people doing open source Computer Graphics software.
Anyway, I'm still looking for.
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hi, there
It's my first time to post a question here to ask for help because the problem is drving me crazy. Everyone who give a direct answer or redirect-url resources is appreciable.
here is the problem:
I decide to grab web-pages from a website, what my policy is that I use a main thread to find many items in a page and i send each item to a thread to deal with. So this is a parallel muti-thread problem. and I find out that the whole process stuck somewhere and the usage of the CPU climed up to 100%. here is the main code that i think is asscociated:
<pre>
HANDLE hSemaThr,hSema,hContent;
main(){
....Handle hCont=CreateFile(....);
hSema=CREATESemaphore(0,1,1,0);
hSemaThr=CREATEMUTEX(0,10,10,0);//this Semaphore is to control thread-buildings so that there are 10 threads in the process at most
WHILE(regex_search(begin,end,stringmatch,r)){
string s=stringmatch[0];
begin=stringmatch[0].second;
WaitForSingleObject(hSemaThr,INFINITE);
CreateThread(0,0,Grab,(void*)dc,0,0);
}
CloseHandle(hCont);
}
void Grab(void* doc){
......
......
WaitForSingleObject(hSema,INFINITE);
if(!WriteFile(::hCont,lpBuf,(int)strlen(lpBuf),&lpN,0)){
cout < <"can't write file in thread" < <GetLastError() < <endl;
//system("pause");
}
ReleaseSemaphore(hSema,1,0);
WaitForSingleObject(hMutexThr,INFINITE);
CanThr--;
ReleaseSemaphore(hSemaThr,1,0);
}
</pre>
Can somebody help me!
Thanks very much!
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sorry, when i extrat my code i forget to change some words:
here is the right one and I have release the semaphore in each thread, right in front of "return", and I know the queuing policy is better but I just want to find out what's wrong with my program,by the way at the same time there can only be 10 threads because of my semaphore controling policy.see"//"
<pre>main(){
....Handle hCont=CreateFile(....);
hSema=CREATESemaphore(0,1,1,0);
hSemaThr=CREATEMUTEX(0,10,10,0);//so there are only 10 threads at most in the same time
WHILE(regex_search(begin,end,stringmatch,r)){
string s=stringmatch[0];
begin=stringmatch[0].second;
WaitForSingleObject(hSemaThr,INFINITE);
CreateThread(0,0,Grab,(void*)dc,0,0);
}
CloseHandle(hCont);
}
void Grab(void* doc){
......
......
WaitForSingleObject(hSema,INFINITE);
if(!WriteFile(::hCont,lpBuf,(int)strlen(lpBuf),&lpN,0)){
cout < <"can't write file in thread" < <GetLastError() < <endl;
//system("pause");
}
ReleaseSemaphore(hSema,1,0);
ReleaseSemaphore(hSemaThr,1,0);
return;
}</pre>
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sorry, when i extrat my code i forget to change some words:
<pre>main(){
....Handle hCont=CreateFile(....);
hSema=CREATESemaphore(0,1,1,0);
hSemaThr=CREATEMUTEX(0,10,10,0);//so there are only 10 threads at most in the same time
WHILE(regex_search(begin,end,stringmatch,r)){
string s=stringmatch[0];
begin=stringmatch[0].second;
WaitForSingleObject(hSemaThr,INFINITE);
CreateThread(0,0,Grab,(void*)dc,0,0);
}
CloseHandle(hCont);
}
void Grab(void* doc){
......
......
WaitForSingleObject(hSema,INFINITE);
if(!WriteFile(::hCont,lpBuf,(int)strlen(lpBuf),&lpN,0)){
cout < <"can't write file in thread" < <GetLastError() < <endl;
//system("pause");
}
ReleaseSemaphore(hSema,1,0);
ReleaseSemaphore(hSemaThr,1,0);
return;
}</pre>
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Problem:
------------------------------------------------------------------------------------------------------
Let have a sequence of K positive finite integers, starting with 1 and ending with K (each element of this sequence represents a free slot) and an arbitrary multiset of L integers of size 1..K.
Using a greedy algorithm, try to fill slots of this sequence with multiset elements, so that the sequence will be the most similar to entered multiset. Similarity is defined as a minimal sum of
absolute values of subtraction of filled sequence slots and elements, which were put in sequence slots.
Examples:
K=3
Multiset = {1,1,1}
Filled_sequence= 1[1] 2[1] 3[1]
Minimal sum = abs(1-1) + abs(2-1) + abs(3-1)= 3
K=5
Multiset = {1,2,3,4,5}
Filled_sequence= 1[1] 2[2] 3[3] 4[4] 5[5]
Minimal sum = abs(1-1) + abs(2-2) + abs(3-3) + abs(4-4) + abs(5-5) = 0
K=7
Multiset = {2,2,4,4,6,6,6}
Filled_sequence= 1[2] 2[2] 3[4] 4[4] 5[6] 6[6] 7[6]
Minimal sum = abs(1-2) + abs(2-2) + abs(3-4) + abs(4-4) + abs(5-6) + abs(6-6) + abs(7-6) = 4
K=7
Multiset = {1,1,7,7}
Filled_sequence= 1[1] 2[1] 3[-] 4[-] 5[-] 6[7] 7[7]
Minimal sum = abs(1-1) + abs(2-1) + abs(6-7) + abs(7-7) = 2
------------------------------------------------------------------------------------------------------
I could think of some greedy approaches, but cannot really determine if they really work, or even if they really are greedy. Could you write me a way, or at least idea how to implement this?
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In order to analyse this problem more deeply we need to create the following structure.
First for each set of equal elements there is one position that is the best. For 55555 it is 3[5]4[5]5[5]6[5]7[5] and similarity is 6. If the number of elements is even we have two possibilities 7777 is 5[7]6[7]7[7]8[7] or 6[7]7[7]8[7]9[7], similarity = 4.
Now if we place every group of equal elements into their best positions and it turns out that they do not overlap, that is the best solution. But they may overlap.
*******aaaaa
**********bbbbbbb
************ccccccccc
**************ddddddddd
In that case we have to slide and cross them around to avoid overlapping but still to get the best result regarding similarity.
Now each position has its similarity value regarding the distance from the optimal 0 valued position of an element. For example for 5 and 9 we have
1 2 3 4 5 6 7 8 9 position
4 3 2 1 0 1 2 3 4 = S[5]
8 7 6 5 4 3 2 1 0 = S[9]
Once you have these values you can create a table if you like, though the table content is obvious. Now assume that multiset has these elements a1 a2 a3 a4 ... ai, repeated n1 n2 n3 n4... ni times. The table is easy to create:
0102030405060708091011...
... = S[a1]
... = S[a2]
... = S[a3]
...
... = S[ai]
Now you go: select n1 positions for element a1, then another not yet selected n2 positions for a2, then another n3 not yet selected positions for a3... and finally ni for ai.
Calculate the similarity.
Keep controllably changing selected ni positions for element ai, then for a,i-1 a,i-2.... This is simply an extend algorithm for creating combinations. You will have to check
|n over n1|*|(n-n1) over n2|*|(n-n1-n2) over n3|*|(n-n1-n2-n3) over n4|*...|(n-n1-...) over ni|
This is quite a number!
I can create heuristics but for a precise algorithm you would probably need something at least as strong as knapsack problem.
Overlapping check is something I would start with, for sure.
Another related idea is not to select all positions for one element first, but rather to select one position for a1 then one position for a2.., and so on until ai. Then to select the position for the second a1 element (if we have it), the second a2 element... second ai element. If you start this way here then you might start with placing each first element into position with value 0.
This second solution can lead to some clever heuristics.
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One of the easy heuristics to implement is to merge two overlapping sections this way:
1. we find two sections overlapping (generally they may have different elements)
******abcdefgh**********************
**********mnopqrstuvw***************
2. make room for insertion using the most optimal way for each section (they both may slide around or whatever looks easy to implement)
********abc*d*ef**g*h****************
***********m*n**op*q*rstuvw**********
3. merge
********abcmdnefopgqhrstuvw**********
An extended heuristic, which would lead to a greedy method, is to allow in step 2. to change the order of elements in each section.
The idea is coming from almost the same problem in 2- or 3-dimension which looks very interesting
circle 1
****************
********ooo*****
*******ooooo****
********ooo*****
****************
{merge with}
circle 2
****************
******yyyy******
*****yyyyyy*****
****yyyyyyyy****
*****yyyyyy*****
******yyyy******
****************
a possible good merge:
*******************
*****yyyy**********
***yyyyyoyoo*******
**yyyyyoyoyoyoo****
***yyyyyoyoo*******
*****yyyy**********
*******************
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Floating point values don't support bitwise operations:
CS0019: Operator '&' cannot be applied to operands of type 'double' and 'double'
CS0019: Operator '|' cannot be applied to operands of type 'double' and 'double'
CS0019: Operator '^' cannot be applied to operands of type 'double' and 'double'
which makes sense in general. I'm working on an interface that I want to have support the built-in numeric types, inluding foating point, and I want to include bitwise operations.
I could simply have the bitwise methods for floating point types throw a NotImplementedException or some such. But I'd prefer to do the best I can, so at this point I have them cast to Int64 and back; so 5.0 | 2.0 ==> 7.0
Have any of you done anything like this? What did you do? Do you find this to be a reasonable solution?
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Is that really what you get when doing a bitwise or of the float values? IIRC they're stored as 1.01 * 2^(01) and 1.00 * 2^(01); so doing a bitwise or you should get 1.01 * 2^(11) = 10.
(all assuming my brain isn't totally fried this morning)
Today's lesson is brought to you by the word "niggardly". Remember kids, don't attribute to racism what can be explained by Scandinavian language roots.
-- Robert Royall
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IIRC they're stored as 1.01 * 2^(01) and 1.00 * 2^(01); so doing a bitwise or you should get 1.01 * 2^(11) = 10.
It would be more natural to treat floating-point numbers for Boolean operators the same as with arithmetic operators: line up the binary point and then process them bit-wise, keeping the most significant bits of the result. Thus, e.g., 1.5 xor 4.75 would be 5.25 (001.10 xor 100.11 is 101.01). Boolean and/or/xor/andNot operators would work as expected for integers that are within precision limits. Other operators involving inversion would be problematic, however.
The difficulty is that while leading 1's can be represented by negative numbers (thanks to the fact that sum[n=0..inf](2^n)=-1)  trailing 1's cannot be represented in floating-point in any manner that will persist. The floating-point value "not 0" should be "-epsilon", which should have all bits set to the left and right of the binary point. Any value--no matter how larger or small--that is and'ed with "not 0" should yield itself. The value "not 1" should have all bits set except for bit 0, and should be the same as "(not 0) - 1". And'ing any value (no matter the magnitude) with that quantity should leave all bits other than bit 0. Unfortunately, -1-epsilon is going to get rounded to -1, which will have all bits to the left of the binary point (including bit 0) set, and all bits to the right clear.
I think the Boolean operators and/or/xor/andNot could be sensibly applied to floating-point numbers, but I don't see any good way of handling the rest. Note that the normal equality (x and y)=(x andNot (-1-y)) which is applicable to integers would not apply with floats, however (with integers, 'not 0' is -1, but with floats it isn't).
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I have to disagree. Bitwise operators should by definition be data agnostic and only look at the raw bits.
Today's lesson is brought to you by the word "niggardly". Remember kids, don't attribute to racism what can be explained by Scandinavian language roots.
-- Robert Royall
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I have to disagree. Bitwise operators should by definition be data agnostic and only look at the raw bits.
In C, the bitwise operators are not data agnostic. Their particular behavior was chosen to match the behavior of many common architectures, but on architectures which store things differently, the behavior of bitwise operators is required to emulate the common hardware rather than operate on the actual stored bits.
For example, on many machines the 16-bit quantity -5 is represented as 1111111111111011. On some it would have been represented as 1000000000000101. On either type of machine, however, the C standard specifies that (-5 & 12)==8.
I can imagine scenarios where it would be useful to apply Boolean operators to fractional numbers using aligned-binary-point maths; I can't imagine any scenario where applying Boolean operators to the binary representation of floating-point numbers would yield anything of value except in cases aligned-binary-point math would be just as useful (indeed, just about the only scenario I can see having any use would be or'ing a bunch of numbers to see if any are negative or exceed some particular magnitude).
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This response and it's thread point out why bitwise operators are not usually supported.
Yes, I could perform an actual bitwise operation on the underlying bytes, but I don't think the result would be what the user expects, and the resultant pattern of bits may not even be a valid value for its type.
Which is why I would rather have them match their integer counterparts. If someone has 5 and 2 in floating point variables, and is foolish enough to perform Or on them, wouldn't 7 be the expected result? If not, then I'd rather not implement them at all.
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Hii
I used the code to calcalate the intersection if any between 2 lines, but how to do it between lines and arcs , and arcs to arcs ?
The time i did Math is already 20 years ago ....
Johan
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These primitives are all simplexes as such can be represented in parametric form, where by the intersections are solutions to the parametric form equations, Dave Eberly's Geometric tools site has code and documentation explaining the concepts for each pair combination.
Geometric Tools[^]
A side note for regular arc to arc or line or line-segment intersections you can perform the intersections upon the basis circle of the arc (becoming circle-circle, circle-line, circle-line-segment) and then to determine if there is an intersection see if the computerd intersection(s) exists upon the arc itself. The following has some examples:
Wykobi Article[^]
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Hi
Thanks, looks good, i will try to translate the ones i need to c# (cpp is not my stuff)
Johan
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