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Image/Texture scroll/shift (wrap)

Does anyone know whether libGDX has a method for scrolling/shifting an image/texture within itself?
To explain; I would like to be able to scroll the contents (pixels) of an image, either vertically or horizontally within its own region. For example, if an image is shifted 1 pixel to the right, all pixels move 1 to the right and those on the right-most-edge are wrapped to the left-most-edge. The image size does not change, only the positioning of the pixels within it change.
I have mainly been working with the Sprite class, it can do a lot (scale, rotate, etc) but shift/scroll as I need it, isn't there.
Before writting the method myself, I thought I'd ask here...
The following worked for me, this was provided by Kush:
float delta = 0f;
// In the Actors act method
delta += Gdx.graphics.getDeltaTime();
// Horizontal
batch.draw(texture, 0, 0, width, height, 0 + delta * 10, 1, 1 + delta * 10, 0);
// Vertical
batch.draw(texture, 0, 0, width, height, 1, 0 + delta * 10, 0, 1 + delta * 10);

You won't need Sprite for this, draw directly Texture using batch. For wrapping first set
Texture texture = new Texture("example.png");
texture.setWrap(TextureWrap.Repeat, TextureWrap.Repeat);
then draw using uv
batch.draw(texture, x, y, width, height, u, v, u2, v2);
or any other method that suits you in SpriteBatch.

opengl rotation texture off center

I wrote some code to get a plain 2d box to face the mouse. It rotated just fine around its center, and everything was working great, but when i put a texture on the box, it did not rotate around the center anymore.
The code:
float imgWidth = texture.getImageWidth()*scale;
float imgHeight = texture.getImageHeight()*scale;
glLoadIdentity();
texture.bind();
glTranslatef(x, y, 0);
glRotated(rotation - 90, 0, 0, 360);
glBegin(GL_QUADS);
glTexCoord2f(0, 0);
glVertex2f(-imgWidth, -imgHeight);
glTexCoord2f(1, 0);
glVertex2f(imgWidth, -imgHeight);
glTexCoord2f(1,1);
glVertex2f(imgWidth, imgHeight);
glTexCoord2f(0, 1);
glVertex2f(-imgWidth, imgHeight);
glEnd();

The answer is simple but with a complicated background that has to be understood.
OpenGL always rotate something not around its center but takes as center the point (0;0).
This can be an issue because if you translate your object somewhere and then your rotate it, it will rotate not on its center but around the (0;0) point (origin) creating a big rotation, I will say as a planet around the Sun.
Also OpenGL works with matrix, that with very barbaric simplification means that the operation are executed bottom to top.
// store the current model matrix
GL11.glPushMatrix();
// bind to the appropriate texture for this image
this.texture.bind();
// translate to the right location and prepare to draw
GL11.glColor3f(1, 1, 1);
GL11.glTranslated(x + (this.texture.getImageWidth() / 2), y + (this.texture.getImageHeight() / 2), 0);
GL11.glRotated(this.angle, 0, 0, 1);
GL11.glTranslated(-this.texture.getImageWidth() / 2, -this.texture.getImageHeight() / 2, 0);
// draw a quad textured to match the sprite
GL11.glBegin(GL11.GL_QUADS);
{
GL11.glTexCoord2f(0, 0);
GL11.glVertex2f(0, 0);
GL11.glTexCoord2f(0, this.texture.getHeight());
GL11.glVertex2f(0, this.texture.getImageHeight());
GL11.glTexCoord2f(this.texture.getWidth(), this.texture.getHeight());
GL11.glVertex2f(this.texture.getImageWidth(), this.texture.getImageHeight());
GL11.glTexCoord2f(this.texture.getWidth(), 0);
GL11.glVertex2f(this.texture.getImageWidth(), 0);
}
GL11.glEnd();
// restore the model view matrix to prevent contamination
GL11.glPopMatrix();
This means that first I am moving the texture to have its center positioned at (0;0) that means translating it backward half the dimensions.
Then I rotate it, and this is the crucial point, because you are using a strange way to rotate it, maybe the problem it's here, take a look to the javadoc:
SPECIFICATION
void glRotated( GLdouble angle,<br>
GLdouble x,<br>
GLdouble y,<br>
GLdouble z )<br>
void glRotatef( GLfloat angle,<br>
GLfloat x,<br>
GLfloat y,<br>
GLfloat z )<br>
PARAMETERS<br>
angle Specifies the angle of rotation, in degrees.
x, y, z<br>
Specify the x, y, and z coordinates of a vector, respectively.
DESCRIPTION<br>
glRotate produces a rotation of angle degrees around the<br>
vector (x,y,z).
First of all all x,y,z values should be between 0 and 1, if you want to rotate a 2d image then you should use the z axis, so the third param will be 1 that mean that you are rotating your image around the unit vector z.
The angle should be in degree and can be either positive or negative.
Try to change your code according to the documentation and you will have your problem solved.
Also with your quad you are drawing a 2x scaled quad, you are starting from -imageWidth to +imageWidth that means 2 times the width...

Why is my floor not flat to the ground?

I want it to be at 0 on the y-axis, that is what I mean by flat to the ground.
I am making the floor of my game in android, I am using opengl es 1. I have a square I am using as the floor, so obviously I want it to be flat to the ground. I want the y-axis to be 0, but whenever I set it to this the square isn't on the screen. But if I set all of the y-axis to 0.1 then the square is hovering from the center of the screen to the top right corner, not flat to the ground.
This is the vertices array:
float w = 10;
float h = 10;
float vertices[] ={
0f, 0.1f, 0f,
w, 0.1f, 0f,
0f, 0.1f, -h,
w, 0.1f, -h
};
I am then storing it in the normal float buffer:
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
vbb.order(ByteOrder.nativeOrder());
mFVertexBuffer = vbb.asFloatBuffer();
mFVertexBuffer.put(vertices);
mFVertexBuffer.position(0);
And then when it comes to drawing it:
gl.glDrawElements( GL10.GL_TRIANGLES,2*3, GL10.GL_UNSIGNED_BYTE, mIndexBuffer);
And this is setting up the frustum, which I don't think should make a difference but...
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
float aspectRatio;
float zNear =.1f;
float zFar = 1000f;
float fieldOfView = 1f;
float size;
gl.glEnable(GL10.GL_NORMALIZE);
aspectRatio=(float)width/(float)height;
gl.glMatrixMode(GL10.GL_PROJECTION);
size = zNear * (float)(Math.tan((double)(fieldOfView/2.0f)));
gl.glFrustumf(-size, size, -size /aspectRatio,
size /aspectRatio, zNear, zFar);
gl.glMatrixMode(GL10.GL_MODELVIEW);
}
Why is it not flat? and why when the y-axis is 0, does it disappear?
I am tring to achieve this:
Where the white section is the floor.

Your object is "disappearing", because your object has no height.
It's like if you were holding an infinitely thin piece of paper flat in front of your eyes. If the paper is above or below your field of vision, then you can see it, but if you put it exactly parallel to your eyes, you wouldn't be able to see it.
It's not really clear to me what you expect it to look like. How do you want this floor to look, will you be looking at it from above, or from an angle? Do you want it to fill from the center of the screen to the bottom? Maybe a mockup image could really help explain what you're trying to achieve.

Android OpenGL ES ortho strange aspect ratio

I'm quite new to OpenGL ES and I'm trying to draw some textured quads. I want to keep it 2D so I decided to use orthographic projection. What I really want is to draw a plane that takes the same relative amount of screen space on every device regardless the screen resolution.
The problem I encounter is the setup of the orthographic projection. The aspect ratio just isn't correct. A square is drawn as a rectangle in the height. This is my code so far:
The Renderer:
// automatically looped by android
public void onDrawFrame(GL10 gl) {
// clear screen and buffer
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
// Draw elements
for (GameObject object : level.getGameObjects()) {
gl.glScalef(0.2f, 0.2f, 0.0f);
object.draw(gl);
gl.glLoadIdentity();
}
}
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
gl.glOrthof(0f, 480f, 0f, 800f, -1f, 1f);
}
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
// Load all textures
for (GameObject object : level.getGameObjects()) {
object.bindTexture(gl);
}
// Initialize game canvas
gl.glEnable(GL10.GL_TEXTURE_2D); // Enable Texture Mapping
gl.glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black background
// enable texture transparency
gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
}
The draw method is exactly the same as in this tutorial: http://obviam.net/index.php/texture-mapping-opengl-android-displaying-images-using-opengl-and-squares/
Kind regards,
Daan

Why are you hardcoding the width and height to glOrthof? Shouldn't you use the passed in width and height?
gl.glOrthof(0f, width, 0f, height, -1f, 1f);

I have found the answer to my problem. First of all I was hardcoding the width and height wich wasn't a good option. To have a fixed with on all screen resolutions i now calculate the aspect ratio and for the height I use the with multiplied by the aspect ratio.
Another problem was the fact that I hadn't reset the projection matrix prior to setting the glortho. I have changed all this and it solved the problem:
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glOrthof(0f, 320, 0f, 320*aspect, -1f, 1f);
}
I hope this will be helpfull for somebody.
Kind regards,
Daan

Looks like you've solved it. Can you provide details on how you calculated the aspect variable (a division of height and width perhaps?) Just as an FYI, the height and width values passed in to the onSurfaceChanged() event are indeed dynamic. For instance, they are reversed when you flip the screen orientation.
I'm relatively new to this as well, but in my desktop gl experience, it's important to factor these in when a window size changes.

Problems rendering to texture - scaling issues(?)

I'm trying to get my rendering-to-texture working. So far, it does all the necessary GL gubbins to draw on the texture and everything - the only problem is its getting the scaling all off.
I figured I'd want to set the viewport to the size of the texture, and the gluOrtho2d (the way I'm going to be drawing onto the texture) as -halfwidth, halfwidth, -halfheight, halfheight. This means when drawing position 0,0 should be in the center. A position of halfwdith, halfheight should be in the top right corner etc etc.
I'm getting really weird effects though, it seems that its not drawing on the texture in the right scale - so everything gets skewed, can anyone suggest what I might be doing wrong?
Thanks
public void renderToTexture(GLRenderer glRenderer, GL10 gl)
{
boolean checkIfContextSupportsExtension = checkIfContextSupportsExtension(gl, "GL_OES_framebuffer_object");
if(checkIfContextSupportsExtension)
{
GL11ExtensionPack gl11ep = (GL11ExtensionPack) gl;
int mFrameBuffer = createFrameBuffer(gl,texture.getWidth(), texture.getHeight(), texture.getGLID());
if (mFrameBuffer == -1)
{
return;
}
gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, mFrameBuffer);
int halfWidth = texture.getWidth()/2;//width/2;
int halfHeight = texture.getHeight()/2;//height/2;
gl.glViewport(0,0,texture.getWidth(), texture.getHeight());
gl.glLoadIdentity();
GLU.gluOrtho2D(gl, -halfWidth, halfWidth , -halfHeight, halfHeight);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
gl.glClearColor(0f, 1f, 0f, 1f);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
//draw the old version of the texture to framebuffer:
Quad quad = new Quad(texture.getWidth(), texture.getHeight());
quad.setTexture(texture);
SpriteRenderable sr = new SpriteRenderable(quad);
sr.renderTo(glRenderer, gl, 1);
//draw the new gl objects etc to framebuffer
for (Renderable renderable : renderThese)
{
if (renderable.isVisible()) {
renderable.renderTo(glRenderer, gl, 1);
}
}
//default to the old framebuffer
gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, 0);
}
}
images:
This one is the game prior to any texture rendering.
image1
This is after the "blood splats" (currently pigs!) are rendered on the "arena" background texture shown in picture 1. Notice that the original texture has shrunk too small to see in the middle (its a few pixles) and the pig "blood splat" jumps in a zig-zag, flipping over the center of the texture and becoming smaller...
image2
(sorry, dont have enough rep to post images in the post!)

Just a speculative guess, but do you remember to set matrixMode to GL_PROJECTION prior to entering renderToTexture function? It's not set inside the function, where it seems like it should be. Also don't forget to restore projection matrix and viewport at the end of the function.