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Fix some grammar, punctuation, spelling and compliance with the GDScript style guide in custom_drawing_in_2d.rst (#2026)

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corrigentia
2018-12-12 12:49:04 +02:00
committed by Rémi Verschelde
parent 873b372a1f
commit cac444f42b
1 changed files with 34 additions and 34 deletions
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68
tutorials/2d/custom_drawing_in_2d.rst
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@@ -7,11 +7,11 @@ Why?
----
Godot has nodes to draw sprites, polygons, particles, and all sorts of
stuff. For most cases this is enough but not always. Before crying in fear,
stuff. For most cases, this is enough; but not always. Before crying in fear,
angst, and rage because a node to draw that specific *something* does not exist...
it would be good to know that it is possible to easily make any 2D node (be it
:ref:`Control <class_Control>` or :ref:`Node2D <class_Node2D>`
based) draw custom commands. It is *really* easy to do it too.
based) draw custom commands. It is *really* easy to do it, too.
But...
------
@@ -27,8 +27,8 @@ examples why:
the blocks.
- Managing drawing logic of a large amount of simple objects (in the
hundreds of thousands). Using a thousand nodes is probably not nearly
as efficient as drawing, but a thousand of draw calls are cheap.
Check the "Shower of Bullets" demo as example.
as efficient as drawing, but a thousand draw calls are cheap;
take the "Shower of Bullets" demo as an example.
- Making a custom UI control. There are plenty of controls available,
but it's easy to run into the need to make a new, custom one.
@@ -68,7 +68,7 @@ If re-drawing is required because a state or something else changed,
simply call :ref:`CanvasItem.update() <class_CanvasItem_update>`
in that same node and a new _draw() call will happen.
Here is a little more complex example. A texture variable that will be
Here is a little more complex example, a texture variable that will be
redrawn if modified:
.. tabs::
@@ -76,10 +76,10 @@ redrawn if modified:
extends Node2D
export var texture setget _set_texture
export (Texture) var texture setget _set_texture
func _set_texture(value):
# if the texture variable is modified externally,
# If the texture variable is modified externally,
# this callback is called.
texture = value #texture was changed
update() # update the node
@@ -154,17 +154,17 @@ portion of a circle? You will have to code a function to perform this and draw i
Arc function
^^^^^^^^^^^^
An arc is defined by its support circle parameters. That is: the center position
An arc is defined by its support circle parameters, that is, the center position
and the radius. The arc itself is then defined by the angle it starts from
and the angle at which it stops. These are the 4 parameters that we have to provide to our drawing.
and the angle at which it stops. These are the 4 arguments that we have to provide to our drawing function.
We'll also provide the color value, so we can draw the arc in different colors if we wish.
Basically, drawing a shape on screen requires it to be decomposed into a certain number of points
linked from one to the following one. As you can imagine, the more points your shape is made of,
Basically, drawing a shape on the screen requires it to be decomposed into a certain number of points
linked from one to the next. As you can imagine, the more points your shape is made of,
the smoother it will appear, but the heavier it will also be in terms of processing cost. In general,
if your shape is huge (or in 3D, close to the camera), it will require more points to be drawn without
it being angular-looking. On the contrary, if your shape is small (or in 3D, far from the camera),
you may reduce its number of points to save processing costs. This is called *Level of Detail (LoD)*.
you may decrease its number of points to save processing costs; this is known as *Level of Detail (LoD)*.
In our example, we will simply use a fixed number of points, no matter the radius.
.. tabs::
@@ -174,7 +174,7 @@ In our example, we will simply use a fixed number of points, no matter the radiu
var nb_points = 32
var points_arc = PoolVector2Array()
for i in range(nb_points+1):
for i in range(nb_points + 1):
var angle_point = deg2rad(angle_from + i * (angle_to-angle_from) / nb_points - 90)
points_arc.push_back(center + Vector2(cos(angle_point), sin(angle_point)) * radius)
@@ -200,18 +200,18 @@ In our example, we will simply use a fixed number of points, no matter the radiu
Remember the number of points our shape has to be decomposed into? We fixed this
number in the nb_points variable to a value of 32. Then, we initialize an empty
PoolVector2Array, which is simply an array of Vector2.
number in the ``nb_points`` variable to a value of ``32``. Then, we initialize an empty
``PoolVector2Array``, which is simply an array of ``Vector2``s.
The next step consists of computing the actual positions of these 32 points that
compose an arc. This is done in the first for-loop: we iterate over the number of
points for which we want to compute the positions, plus one to include the last point.
We first determine the angle of each point, between the starting and ending angles.
The reason why each angle is reduced by 90° is that we will compute 2D positions
The reason why each angle is decreased by 90° is that we will compute 2D positions
out of each angle using trigonometry (you know, cosine and sine stuff...). However,
to be simple, cos() and sin() use radians, not degrees. The angle of 0° (0 radian)
starts at 3 o'clock although we want to start counting at 12 o'clock. So we reduce
starts at 3 o'clock, although we want to start counting at 12 o'clock. So we decrease
each angle by 90° in order to start counting from 12 o'clock.
The actual position of a point located on a circle at angle 'angle' (in radians)
@@ -225,17 +225,17 @@ Finally, we insert the point in the PoolVector2Array which was previously define
Now, we need to actually draw our points. As you can imagine, we will not simply
draw our 32 points: we need to draw everything that is between each of them.
We could have computed every point ourselves using the previous method, and drew
it one by one. But this is too complicated and inefficient (except if explicitly needed).
So, we simply draw lines between each pair of points. Unless the radius of our
it one by one. But this is too complicated and inefficient (except if explicitly needed),
so we simply draw lines between each pair of points. Unless the radius of our
support circle is big, the length of each line between a pair of points will
never be long enough to see them. If this happens, we simply would need to
never be long enough to see them. If that were to happen, we would simply need to
increase the number of points.
Draw the arc on screen
^^^^^^^^^^^^^^^^^^^^^^
Draw the arc on the screen
^^^^^^^^^^^^^^^^^^^^^^^^^^
We now have a function that draws stuff on the screen:
It is time to call in the _draw() function.
We now have a function that draws stuff on the screen;
it is time to call it inside the _draw() function:
.. tabs::
@@ -270,7 +270,7 @@ Arc polygon function
We can take this a step further and not only write a function that draws the plain
portion of the disc defined by the arc, but also its shape. The method is exactly
the same as previously, except that we draw a polygon instead of lines:
the same as before, except that we draw a polygon instead of lines:
.. tabs::
.. code-tab:: gdscript GDScript
@@ -281,7 +281,7 @@ the same as previously, except that we draw a polygon instead of lines:
points_arc.push_back(center)
var colors = PoolColorArray([color])
for i in range(nb_points+1):
for i in range(nb_points + 1):
var angle_point = deg2rad(angle_from + i * (angle_to - angle_from) / nb_points - 90)
points_arc.push_back(center + Vector2(cos(angle_point), sin(angle_point)) * radius)
draw_polygon(points_arc, colors)
@@ -310,8 +310,8 @@ the same as previously, except that we draw a polygon instead of lines:
Dynamic custom drawing
^^^^^^^^^^^^^^^^^^^^^^
Alright, we are now able to draw custom stuff on screen. However, it is static:
Let's make this shape turn around the center. The solution to do this is simply
All right, we are now able to draw custom stuff on the screen. However, it is static;
let's make this shape turn around the center. The solution to do this is simply
to change the angle_from and angle_to values over time. For our example,
we will simply increment them by 50. This increment value has to remain
constant or else the rotation speed will change accordingly.
@@ -364,7 +364,7 @@ calls _draw(). This way, you can control when you want to refresh the frame.
angle_from += rotation_angle
angle_to += rotation_angle
# We only wrap angles if both of them are bigger than 360
# We only wrap angles when both of them are bigger than 360.
if angle_from > 360 and angle_to > 360:
angle_from = wrap(angle_from, 0, 360)
angle_to = wrap(angle_to, 0, 360)
@@ -384,7 +384,7 @@ calls _draw(). This way, you can control when you want to refresh the frame.
_angleFrom += _rotationAngle;
_angleTo += _rotationAngle;
// We only wrap angles if both of them are bigger than 360
// We only wrap angles when both of them are bigger than 360.
if (_angleFrom > 360 && _angleTo > 360)
{
_angleFrom = Wrap(_angleFrom, 0, 360);
@@ -422,10 +422,10 @@ Let's run!
It works, but the arc is rotating insanely fast! What's wrong?
The reason is that your GPU is actually displaying the frames as fast as it can.
We need to "normalize" the drawing by this speed. To achieve, we have to make
We need to "normalize" the drawing by this speed; to achieve that, we have to make
use of the 'delta' parameter of the _process() function. 'delta' contains the
time elapsed between the two last rendered frames. It is generally small
(about 0.0003 seconds, but this depends on your hardware). So, using 'delta' to
(about 0.0003 seconds, but this depends on your hardware), so using 'delta' to
control your drawing ensures that your program runs at the same speed on
everybody's hardware.
@@ -440,7 +440,7 @@ smaller value, which directly depends on the rendering speed.
angle_from += rotation_angle * delta
angle_to += rotation_angle * delta
# we only wrap angles if both of them are bigger than 360
# We only wrap angles when both of them are bigger than 360.
if angle_from > 360 and angle_to > 360:
angle_from = wrap(angle_from, 0, 360)
angle_to = wrap(angle_to, 0, 360)
@@ -453,7 +453,7 @@ smaller value, which directly depends on the rendering speed.
_angleFrom += _rotationAngle * delta;
_angleTo += _rotationAngle * delta;
// We only wrap angles if both of them are bigger than 360
// We only wrap angles when both of them are bigger than 360.
if (_angleFrom > 360 && _angleTo > 360)
{
_angleFrom = Wrap(_angleFrom, 0, 360);