Scratch

Greatdane wrote:

juststickman wrote:

Has anyone realized that you can just use point towards block, record the angle and them go back to the original direction?
If it has to use trig, copy the point towards script >.>

But we want to use advanced formulas and trigonometry! 

Fine then.

Oh... Yeah! LOL!

GREAT WORK NXIII

How old are you?I'm 15

cds56 wrote:

Subh wrote:

GREAT WORK NXIII

How old are you?I'm 15

nXIII is approximately eight years old.

jk, I don't know really. I would guess that he's around 13 - 16 though..

...eight?

I'm younger than Subh. But I've been using trig for a while, I don't want to sound like I'm bragging or anything (I'm hope it doesn't sound like I am)

Billyedward is smarter than nXIII. 

I wasn't trying to be technical. It was a joke. Hence the 

billyedward wrote:

Well, I wouldn't say that it can be definitively deduced from the scratch forums who is smarter... And I have seen many of the things that nXIII has done, and I must say that he is certainly of a superior intellect to many of us. (who exactly, will remain unnamed)

The other thing to consider is that he is under 15, and older than 8. So we know him to be between the ages of 9 and 14. I on the other hand, am exactly 15. Therefore, on an IQ basis, even if we scored the exact same on a test his would be higher. This must be taken into account on the scratch forums, too.

But shadow_7283, I take your above comment to mean that my solution worked?

It works for the first quadrant only. Atan2 would work for all four quadrants. It also makes the sprite point in the wrong direction due to Scratch's weird angles. With some tweaking it can be made perfect! 

Last edited by MathWizz (2010-06-22 21:36:01)

nXIII wrote:

MathWizz wrote:

billyedward wrote:

Well, I wouldn't say that it can be definitively deduced from the scratch forums who is smarter... And I have seen many of the things that nXIII has done, and I must say that he is certainly of a superior intellect to many of us. (who exactly, will remain unnamed)

The other thing to consider is that he is under 15, and older than 8. So we know him to be between the ages of 9 and 14. I on the other hand, am exactly 15. Therefore, on an IQ basis, even if we scored the exact same on a test his would be higher. This must be taken into account on the scratch forums, too.

But shadow_7283, I take your above comment to mean that my solution worked?

It works for the first quadrant only. Atan2 would work for all four quadrants. It also makes the sprite point in the wrong direction due to Scratch's weird angles. With some tweaking it can be made perfect! 

Which is the basis on which my algorithm is made. I just used arccosine because there is a smaller chance of division by zero when using the hypotenuse.

I see...
That does make sense.
Let me go and revise mine, then, to fix this.

billyedward wrote:

Ok, I fixed it.
Here is the XML code for the working block:

Code:

<?xml version="1.0" encoding="UTF-8" ?><scratchScript><block selector="-"><argument><block selector="+"><argument>-90</argument><argument><block selector="*"><argument>90</argument><argument><block selector="*"><argument><block selector="-"><argument><block selector="computeFunction:of:"><argument>abs</argument><argument><block selector="-"><argument><block selector="\\"><argument><block selector="+"><argument><block selector="rounded"><argument><block selector="computeFunction:of:"><argument>10 ^</argument><argument><block selector="+"><argument><block selector="-"><argument><block selector="mouseX"/></argument><argument><block selector="xpos"/></argument></block></argument><argument>15</argument></block></argument></block></argument></block></argument><argument>0.5</argument></block></argument><argument>2</argument></block></argument><argument>1</argument></block></argument></block></argument><argument>0.5</argument></block></argument><argument>4</argument></block></argument></block></argument></block></argument><argument><block selector="computeFunction:of:"><argument>atan</argument><argument><block selector="dividedBy"><argument><block selector="-"><argument><block selector="ypos"/></argument><argument><block selector="mouseY"/></argument></block></argument><argument><block selector="+"><argument><block selector="-"><argument><block selector="xpos"/></argument><argument><block selector="mouseX"/></argument></block></argument><argument>1.0e-14</argument></block></argument></block></argument></block></argument></block></scratchScript>

It is a MASSIVE binomial.
The second term is basically the above, with 0.0000000000001 added to the denominator to avoid division by zero.

The first is a LONG, but foolproof mathematical way of taking any number, and returning it's sign. I need this, as TAN cannot distinguish between positive and negative angles, as all slopes (the argument) are bidirectional. So I need to do that conversion myself, via this first term. I just came up with this now, but if anyone else has a simpler mathematical way of deducing the sign of a number, please tell me.

That's really cool but... I don't understand any of the XML.

Oh well.

I need help with something else.
What is the best way to draw a circle? I have tried to repeat a block 360 times (but it crowded the scripts to much and was a pain to edit). I tried using the atomic feature in BYOB (but even that didn't draw fast enough). And I tried yelling at it (but it didn't work).

Any ideas how I can draw a circle efficiently with a pen? Please note that it won't remain a circle. It's shape will be transformed.

billyedward wrote:

Ok, I fixed it.
Here is the XML code for the working block:

Code:

<?xml version="1.0" encoding="UTF-8" ?><scratchScript><block selector="-"><argument><block selector="+"><argument>-90</argument><argument><block selector="*"><argument>90</argument><argument><block selector="*"><argument><block selector="-"><argument><block selector="computeFunction:of:"><argument>abs</argument><argument><block selector="-"><argument><block selector="\\"><argument><block selector="+"><argument><block selector="rounded"><argument><block selector="computeFunction:of:"><argument>10 ^</argument><argument><block selector="+"><argument><block selector="-"><argument><block selector="mouseX"/></argument><argument><block selector="xpos"/></argument></block></argument><argument>15</argument></block></argument></block></argument></block></argument><argument>0.5</argument></block></argument><argument>2</argument></block></argument><argument>1</argument></block></argument></block></argument><argument>0.5</argument></block></argument><argument>4</argument></block></argument></block></argument></block></argument><argument><block selector="computeFunction:of:"><argument>atan</argument><argument><block selector="dividedBy"><argument><block selector="-"><argument><block selector="ypos"/></argument><argument><block selector="mouseY"/></argument></block></argument><argument><block selector="+"><argument><block selector="-"><argument><block selector="xpos"/></argument><argument><block selector="mouseX"/></argument></block></argument><argument>1.0e-14</argument></block></argument></block></argument></block></argument></block></scratchScript>

It is a MASSIVE binomial.
The second term is basically the above, with 0.0000000000001 added to the denominator to avoid division by zero.

The first is a LONG, but foolproof mathematical way of taking any number, and returning it's sign. I need this, as TAN cannot distinguish between positive and negative angles, as all slopes (the argument) are bidirectional. So I need to do that conversion myself, via this first term. I just came up with this now, but if anyone else has a simpler mathematical way of deducing the sign of a number, please tell me.

I don't really know what this looks like, but you should probably look at my five-ish-line approach. It's simple, but 100% effective (or is it affective? Ugh, I always remember these things, but now I forget!).

Last edited by nXIII (2010-06-23 16:33:03)

shadow_7283 wrote:

shadow_7283 wrote:

I need help with something else.
What is the best way to draw a circle? I have tried to repeat a block 360 times (but it crowded the scripts to much and was a pain to edit). I tried using the atomic feature in BYOB (but even that didn't draw fast enough). And I tried yelling at it (but it didn't work).

Any ideas how I can draw a circle efficiently with a pen? Please note that it won't remain a circle. It's shape will be transformed.

working on it, BYOB.

shadow_7283 wrote:

What is the best way to draw a circle?

REPEAT 360 [MOVE 1 STEP TURN 1 DEGREE]

but that circle isn't centered on your current position, so you might have to move to its edge first.

The circumference of this circle is (approximately) 360, so its radius is 180/pi.  Adjust the step or the turn if you want a different size.

(Math lesson:  One way to define a circle, the way everyone knows, is that it's the locus of points a fixed distance from a center point.  But another way, provably equivalent, is that a circle is a curve of constant curvature -- it keeps turning by the same amount everywhere.  The program above is based on that understanding: for every little bit you move, you have to turn the same amount (same as the previous turn, I mean, not turn=move).  I think you get this in second semester calculus.    )