I am trying to rotate a Sprite in three dimensions around its centerpoint, and I am struggling to understand some of the behavior of matrix3D.
Ive overridden the set rotationX, rotationY, and rotationZ methods of the Sprite as follows:
override public function set rotationX (_rotationX:Number) : void {
this.transform.matrix3D.prependTranslation(this.width/2.0, this.height/2.0, 0);
this.transform.matrix3D.prependRotation(-this.rotationX, Vector3D.X_AXIS);
this.transform.matrix3D.prependRotation(_rotationX, Vector3D.X_AXIS);
this.transform.matrix3D.prependTranslation(-(this.width/2.0), -(this.height/2.0), 0);
}
override public function set rotationY (_rotationY:Number) : void {
this.transform.matrix3D.prependTranslation(this.width/2.0, this.height/2.0, 0);
this.transform.matrix3D.prependRotation(-this.rotationY, Vector3D.Y_AXIS);
this.transform.matrix3D.prependRotation(_rotationY, Vector3D.Y_AXIS);
this.transform.matrix3D.prependTranslation(-(this.width/2.0), -(this.height/2.0), 0);
}
override public function set rotationZ (_rotationZ:Number) : void {
this.transform.matrix3D.prependTranslation(this.width/2.0, this.height/2.0, 0);
this.transform.matrix3D.prependRotation(-this.rotationZ, Vector3D.Z_AXIS);
this.transform.matrix3D.prependRotation(_rotationZ, Vector3D.Z_AXIS);
this.transform.matrix3D.prependTranslation(-(this.width/2.0), -(this.height/2.0), 0);
}
I am using prependTranslation to correct the centerpoint of the rotation, and the first prependRotation to cancel out any previously-applied rotation.
Testing it out, rotationX works exactly as expected, and the Sprite rotates around its horizontal axis.
rotationY and rotationZ also appear to work fine. However, there is one problem: whenever rotationY or rotationZ are set, all of the other rotation values change as well. This is not a problem with rotationX -- if I set rotationX, nothing else changes. But if I set rotationY or rotationZ all the rotation values change, which is a problem for my app (which is trying to save and restore values).
I think I am just lacking some understanding about what is going on with matrix3D. How can I implement this so there is no interdependence between the values?
Another easy solution is to add the object and center it within a container sprite and do the 3D transformations on the containing sprite.
I know nothing about AS3 etc. But just looking at your code, I wonder why you translate on the z-axis using what I understand to be x and y values (width and height). Shouldn't the z-axis be translated using something like "depth"?
This is very simple, you can try use the following code:
var matrix3d:Matrix3D = s.transform.matrix3D;
matrix3d.appendRotation( -1, Vector3D.Z_AXIS , new Vector3D( 390, 360, 0 ) );
while s is your sprite, the third parameter, Vector3D indicate your sprite's center position.
The Above code will make the sprite s rotate more -1 degree.
Related
So I am developing a game in 2D in Godot and I want to see a line from the center of my sprite to its facing position. I have the sprite rotating and moving along the rotation direction but when I try to create vector out of that its very wrong. For example the vector line is going from the center of the sprite to near (0,0) position on the screen.
public override void _Draw()
{
Vector2 rotationDirection = new Vector2(Mathf.Cos(sprite.GlobalRotation) , Mathf.Sin(sprite.GlobalRotation)) - sprite.GlobalPosition;
DrawLine(sprite.GlobalPosition, rotationDirection, Colors.Red, 2f);
}
EDIT:
Fixed it it works now.
public override void _Draw()
{
DrawLine(sprite.GlobalPosition, sprite.GlobalPosition + new Vector2(Mathf.Cos(sprite.GlobalRotation), Mathf.Sin(sprite.GlobalRotation)) * 50f, Colors.Red, 2f);
}
A simpler solution would have been to add a Line2D child node. You can see the effect right away in the editor, and there's no need for any maths.
This might also be more efficient, because custom _draw functions don't play nice with Godot's geometry batching.
thanks in advance for helping me out.
I'm wrapping up work on a 2D platformer that has a background parallax effect using a texture offset on five different layers. The two cloud layers just have their offset scrolling over time, and the three ground layers scroll based on the camera position. This all works perfectly in Unity and in the PC build and looks great.
However, on the Unity Web Player and webGL builds, instead of the texture wrapping, it looks like this:
I'm new here, so I can't embed images yet it seems
I have no idea what is causing the problem, but instead of wrapping around and acting like a conveyor belt, it just streaks like that. Here is my parallax code:
using UnityEngine;
using System.Collections;
public class sceneryParallax : MonoBehaviour {
[SerializeField]
private Transform cameraTransform;
[SerializeField]
private Renderer renderBGFar;
[SerializeField]
private Renderer renderBGMid;
[SerializeField]
private Renderer renderBGNear;
public float offsetFar;
public float offsetMid;
public float offsetNear;
void Update () {
float xOffset = cameraTransform.position.x;
Vector2 farOffset = new Vector2((xOffset / offsetFar) % 1.0f, 0.0f);
Vector2 midOffset = new Vector2((xOffset / offsetMid) % 1.0f, 0.0f);
Vector2 nearOffset = new Vector2((xOffset / offsetNear) % 1.0f, 0.0f);
renderBGFar.material.mainTextureOffset = farOffset;
renderBGMid.material.mainTextureOffset = midOffset;
renderBGNear.material.mainTextureOffset = nearOffset;
}
}
Also, here is a screen of my texture setup:
Link
Sorry if there are any formatting problems! I really appreciate any help you can offer. If you need more information, let me know!
Thanks!
If your texture wrapping mode is set to clamp, it will reuse the last available pixel. It sounds like texture mode repeat is what you need, opposed to clamping, per the documentation:
This is useful for preventing wrapping artifacts when mapping an image
onto an object and you don't want the texture to tile. UV coordinates
will be clamped to the range 0...1. When UVs are larger than 1 or
smaller than 0, the last pixel at the border will be used. See Also:
Texture.wrapMode, texture assets.
I am rendering a QPixmap inside of a QThread. the code to paint is inside a function. If I declare the painter inside the drawChart function everything seems ok but if I declare the painter inside the run function the image is wrong in the sense that at the edge of a black and white area, the pixels at the interface are overlapped to give a grey. Does anyone know why this is so? Could it be because of the nature of the run function itself?
//This is ok
void RenderThread::run()
{
QImage image(resultSize, QImage::Format_RGB32);
drawChart(&image);
emit renderedImage(image, scaleFactor);
}
drawChart(&image)
{
QPainter painter(image);
painter.doStuff()(;
...
}
//This gives a image that seems to have artifacts
void RenderThread::run()
{
QImage image(resultSize, QImage::Format_RGB32);
QPainter painter(image);
drawChart(painter);
emit renderedImage(image, scaleFactor);
}
drawChart(&painter)
{
painter.doStuff();
...
}
//bad
.
//good
.
From C++ GUI Programming with Qt 4 by Jasmin Blanchette and Mark Summerfield:
One important thing to understand is
that the center of a pixel lies on
“half-pixel” coordinates. For example,
the top-left pixel covers the area
between points (0, 0) and (1, 1), and
its center is located at (0.5, 0.5).
If we ask QPainter to draw a pixel at,
say, (100, 100), it will approximate
the result by shifting the coordinate
by +0.5 in both directions, resulting
in the pixel centered at (100.5,
100.5) being drawn.
This distinction may seem rather
academic at first, but it has
important consequences in practice.
First, the shifting by +0.5 only
occurs if antialiasing is disabled
(the default); if antialiasing is
enabled and we try to draw a pixel at
(100, 100) in black, QPainter will
actually color the four pixels (99.5,
99.5), (99.5, 100.5), (100.5, 99.5), and (100.5, 100.5) light gray, to give
the impression of a pixel lying
exactly at the meeting point of the
four pixels. If this effect is
undesirable, we can avoid it by
specifying half-pixel coordinates, for
example, (100.5, 100.5).
Ok, so I've been trying to get this concept to work for the day now and have had zero luck. I am not so good with math, so any help will be appreciated. I am trying to rotate a centered container from it's center. The problem with this code is when I use the rotatePicture method, it doesn't rotate from the center, instead it rotates from the box's top-left corner. Here's the code...
import mx.effects.Rotate;
private function init():void
{
calculateCoordinates();
}
private function rotateBox():void
{
var m:Matrix = myBox.transform.matrix;
var centerX:Number = myBox.width / 2;
var centerY:Number = myBox.height / 2;
var centerPoint:Point = new Point(centerX, centerY);
var transformPoint:Point= m.transformPoint(centerPoint);
m.translate(-transformPoint.x, -transformPoint.y);
m.rotate(90 * Math.PI / 180);
m.translate(transformPoint.x, transformPoint.y);
myBox.transform.matrix = m;
this.callLater(calculateCoordinates);
//calculateCoordinates();
}
private function calculateCoordinates():void
{
var x : Number = (myBox.parent.width - myBox.width) / 2;
x = x < 0 ? 0 : x;
var y : Number = (myBox.parent.height - myBox.height) / 2;
y = y < 0 ? 0 : y;
myBox.move(x, y);
}
Ok, this was a bit tricky and i'm working out a couple of details, but in case anyone had a similar issue, I found the general answer. Just took a movie break to refresh the brain...
I had to place a variable for how many turns the canvas had rotated which was easy since I was restricting the degrees to only 90. Then I place in a switch statement that tested the turns variable and recalculated the (x,y) coordinates based off of the turns. Since I knew that the Rotate class would create a cooler effect and end with the same result, I ended up using that instead.
Cheers!
I don't know what your background is, but in my experience this is a classic case of "out-thinking yourself".
You've written quite a bit of code to do something that is actually native to the Flash display API's.
Since you seem to be using Flex I'll just tell you that the simple way to achieve this is to dynamically reposition your display clip contents so that the center of your contents is at the 0,0 point of your clip.
This gets harder the more content you have, but if you just have something like an image or a button or what have you, it's really easy to just calculate the height and width, then divide by 2 and subtract.
Then the rotation property will work just fine.
In Flash it's even easier because you can just make a new clip, bind your class to the clip, and place all yours contents in the Flash authoring tool positioned properly for rotation to work as expected.
Yeah, what Back2Dos said.
Personally, I'd wrap the container in another sprite, position it so its center is at (0,0) in that sprites coordinate space, and then just rotate the sprite ... it's simple and robust ...
I'd like to use <s:Rotate> to rotate center. Hope useful to you.
My application is using Qt.
I have a class which is inheriting QGraphicsPixmapItem.
When applying transformations on these items (for instance, rotations), the origin of the item (or the pivot point) is always the top left corner.
I'd like to change this origin, so that, for instance, when setting the position of the item, this would put actually change the center of the pixmap.
Or, if I'm applying a rotation, the rotation's origin would be the center of the pixmap.
I haven't found a way to do it straight out of the box with Qt, so I thougth of reimplementing itemChange() like this :
QVariant JGraphicsPixmapItem::itemChange(GraphicsItemChange Change, const QVariant& rValue)
{
switch (Change)
{
case QGraphicsItem::ItemPositionHasChanged:
// Emulate a pivot point in the center of the image
this->translate(this->boundingRect().width() / 2,
this->boundingRect().height() / 2);
break;
case QGraphicsItem::ItemTransformHasChanged:
break;
}
return QGraphicsItem::itemChange(Change, rValue);
}
I thought this would work, as Qt's doc mentions that the position of an item and its transform matrix are two different concepts.
But it is not working.
Any idea ?
You're overthinking it. QGraphicsPixmapItem already has this functionality built in. See the setOffset method.
So to set the item origin at its centre, just do setOffset( -0.5 * QPointF( width(), height() ) ); every time you set the pixmap.
The Qt-documentation about rotating:
void QGraphicsItem::rotate ( qreal angle )
Rotates the current item
transformation angle degrees clockwise
around its origin. To translate around
an arbitrary point (x, y), you need to
combine translation and rotation with
setTransform().
Example:
// Rotate an item 45 degrees around (0, 0).
item->rotate(45);
// Rotate an item 45 degrees around (x, y).
item->setTransform(QTransform().translate(x, y).rotate(45).translate(-x, -y));
You need to create a rotate function, that translate the object to the parent's (0, 0) corner do the rotation and move the object to the original location.