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LIGHT and OPAQUE materials | How to create SHADOWS | - Scratch Educational Project 3.0 Tutorial - Contenido educativo

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Subido el 6 de mayo de 2021 por Diego M.

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In this video, we learn how to use the PEN tool to show how light interacts with opaque objects.

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Hi everyone! Today we're going to make a natural science educational project to explain light 00:00:00
and the creation of shadows when light interacts with opaque objects. We're basically going to have 00:00:07
a source of light which will be the sun and an opaque object, for example this apple, 00:00:13
and another sprite which will actually create the light rays and will stop either when touching the 00:00:19
edge or when touching the opaque object. And finally we will code it so that it 00:00:26
runs instantly and we don't have to wait to see the shadow and I will give you 00:00:32
some more ideas to improve your project as I usually do. Alright, so if you are 00:00:37
ready let's get started. 00:00:42
so let's begin adding the sprites first of all the Sun and then an opaque object 00:00:45
I'm gonna take the Apple but you can take any object let me make the Sun a 00:00:58
little bit smaller and this time I'm not gonna get rid of the cat because I'm 00:01:03
gonna use the cat to draw the light rays well in fact you can use any sprite to 00:01:08
draw the light rays. I'm gonna make the cat as small as possible, I'm gonna set 00:01:15
size to one and as you see the minimum size is five and I'm gonna go to 00:01:20
backdrops to convert it to bitmap and with the paint bucket I'm gonna make it 00:01:26
black. So let's go back to the code and basically the program is gonna be this 00:01:34
the cat is going to start from the Sun and it's going to move pen down I will 00:01:42
explain to you what that is later and it's going to trace a yellow line it 00:01:48
will stop when it touches the edge it will go back turn one degree and another 00:01:54
line go back another line go back another line and when it is touching the 00:02:01
apple it will also stop because if it continues we are not creating the shadow 00:02:07
so when touching the apple it will stop we'll go back we'll turn make another 00:02:12
ray stop when touching the Apple go back and so on so first of all I'm gonna go 00:02:17
here and I'm going to add the pen which is what we need what I was saying well 00:02:23
I'm gonna do it with the Apple so that you see it clearly look if pennies up 00:02:31
and I move the Apple it doesn't paint anything but well pen up basically is 00:02:37
when you move the pen up you are not touching the piece of paper so if you 00:02:45
are not touching the piece of paper you cannot paint pen down means that I move 00:02:49
the pen down and I'm touching the piece of paper so if I move the Apple with the 00:02:55
pen down it traces a line alright so I'm gonna erase all I'm gonna take the apple 00:03:00
here and let's begin coding I'm gonna go to scratch and in event well we could do 00:03:07
one green flag clicked or when space key pressed when space key pressed first of 00:03:15
all I'm gonna make sure I move the pen up so that I'm not touching the paper 00:03:22
let's say the cat is over here so pen up so that I'm not touching the paper and 00:03:27
now with the pen up I'm gonna move the cat to the Sun so go to Sun and I press 00:03:33
space so now the cat is here and I can put the pen down I think before that at 00:03:42
the beginning I'm going to do some things which could be this look when 00:03:51
green flag clicked I'm going to set paint color to yellow because I don't 00:03:59
want to have blue light rays set pen size this is how big how not how big how 00:04:06
wide these lines are we can leave this number and later we will change the pen 00:04:15
size and you will see the different results that we can obtain and finally 00:04:21
what is the direction the cat is gonna be pointing in at the beginning let's 00:04:26
say for example 45 which is this and when we're moving the direction of the 00:04:30
cat we will reach okay other numbers so that could be so as we were saying when 00:04:38
space key pressed the cat goes to the sun and moves the pen down. With the pen 00:04:46
down and pointing in this direction now we can move the cat. As we have to move 00:04:52
the cat a lot we're going to repeat this movement. So let's put repeat until. So 00:04:59
cat is moving and when does the cat have to stop okay it has to stop when it is touching the edge 00:05:16
or when touching the apple so the cat is going to repeat this until and i put an or until touching 00:05:23
the edge or touching the apple. After this it's going to turn one degree and 00:05:32
again go to the Sun to repeat the process. So it will turn one degree and 00:05:48
then repeat this process I'm gonna do one thing when space key pressed the 00:05:57
first thing we're going to do is erase all so that I press and it draws it has 00:06:06
stopped so now basically it has to repeat this and this and this many times 00:06:13
I'm gonna put the apple here so that you see what happens as you see when it 00:06:22
touches the apple it stops and now that is not touching the apple anymore it 00:06:29
completes and and paints the rest of the screen logically I don't want to be 00:06:38
clicking here whenever I want to repeat this so I have a loop which is gonna be 00:06:45
repeat 100 times for example place it here and now green flag oh well maybe 00:06:51
this point in direction could be here let's begin as you see it works but it 00:07:03
takes a long time and I don't want you to fall asleep so maybe you are 00:07:17
wondering Diego is there way to do it instantly and the answer is yes of 00:07:21
course look I'm gonna go to my blogs and I'm gonna make a blog called light up 00:07:26
and I'm gonna select this run without screen refresh I'm gonna pass it here 00:07:35
and all this this repetition is what has to be done instantly so I put the block 00:07:44
light up here which is the same as all this which is run instantly and now only 00:07:52
by pressing space this is done I'm gonna move the Apple I press space and as you 00:08:00
this works very well so what you have here is the basic project this is very good but probably you 00:08:10
want to make an excellent project and to make an excellent project i'm going to give you some ideas 00:08:17
to make it better for example probably you know that a complete circumference has 360 degrees 00:08:23
so if I repeat this 360 times as I'm turning one degree every time I'm gonna 00:08:35
complete all this so I can put this anywhere spacebar and look I complete it 00:08:44
other things we were saying if I change this which could be here as well all 00:08:52
this could be here okay and we would get rid of the green flag if i set pen size to three 00:09:00
as you see this is quite different because these lines are three pixels wide and not one 00:09:10
if i set this to 10 i basically complete the whole the whole screen all right more things we can do 00:09:17
probably you're wondering if we can add more objects obviously we can 00:09:26
i'm going to add for example a bat and i'm going to put it here but look when i press spacebar 00:09:31
the light race or the cat the sprite stops when touching the apple but it doesn't stop when 00:09:42
touching the bat why because we haven't coded it yet okay in the cat we said that it has to 00:09:48
move until touching it or apple but not until touching the bat so we need an or all this 00:09:55
is going to be here and in this space we add touching bat now spacebar and that works 00:10:04
another thing we can do here in the edition uh screen obviously we can move the object 00:10:17
but if i am trying my game i can't so to be able to move the object here when i am actually playing 00:10:26
i'm gonna go to uh the sun and i could put when green flag clicked 00:10:35
it's here set drag mode to draggable okay so that you can drag the sun look now i can drag it 00:10:44
but i can't drag these two so i'm gonna pass this to the apple and i'm gonna pass this to the bat 00:10:53
green flag and now these three are draggable and i can drag them all right and with this you have 00:11:02
an excellent project if you want to make it brilliant um you could add some uh variables 00:11:09
for example if i want to control the pen size if i want to control 00:11:17
this from the game i can create a variable called pen size in this variable with right click slider 00:11:26
i make it into slider and with right click change slider range the minimum could be one 00:11:37
and the maximum 10. so i'm going to set pen size to this variable so i put this here 00:11:44
now if i put here an 8 we are setting pen size to 8. so 00:11:56
before you press spacebar make sure you click on the screen and as you see i'm going to move 00:12:05
the objects and I'm gonna set pen size to six okay so that works and another 00:12:13
thing that you could add for example I'm just gonna do it in one of the objects 00:12:30
but you could do it in both of them is that we can control the size of the 00:12:34
Apple from the game or the size of the bat as well it's quite similar I'm gonna 00:12:38
make a variable which is going to be apple size again right click slider 00:12:45
right click change slider range and the size could go from 5 to 300 for example 00:12:52
now in the Apple after this I could put forever set size to what I have here so 00:13:01
variables Apple size so you will see now Apple size is tiny because this is zero 00:13:15
but if I increase it it sets pen size so it says Apple size to this number so now 00:13:24
I can move the Apple I can move the bat you could create another variable for 00:13:35
the bat size and do the same as I've done in the apple and spacebar and I 00:13:39
create the shadow so this is the project guys to study shadows and light and how 00:13:46
light interacts with opaque objects I hope you liked it and please do not 00:13:52
forget to send me a project when you have them done alright see you guys bye 00:13:56
bye 00:14:01
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Idioma/s:
es
Autor/es:
Diego Maté Potes
Subido por:
Diego M.
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
43
Fecha:
6 de mayo de 2021 - 8:10
Visibilidad:
Público
Centro:
CP INF-PRI INFANTA LEONOR
Duración:
14′ 23″
Relación de aspecto:
1.78:1
Resolución:
1920x1080 píxeles
Tamaño:
1.12

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