Develop Reference

I can't see the textures behind a texture with alpha channel

I use 2D sprite texture applied to a square with transparent or semi-transparent area but I can't see anything through them (except the background) if there are other textures behind. I can see the background image because I use a transparent GLSurfaceView, the background is applied in a ImageView behind the GLSurfaceView.
My problem in an image:
Actually I use this code in the onSurfaceCreated method:
gl.glEnable(GL10.GL_TEXTURE_2D);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glClearDepthf(1.0f);
gl.glEnable(GL10.GL_DEPTH_TEST);
gl.glDepthFunc(GL10.GL_LEQUAL);
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);
this in onDrawFrame method:
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
mObject1.draw(gl);
mObject2.draw(gl);
and this in draw method of mObject1 and mObject2:
gl.glPushMatrix();
gl.glEnable(GL10.GL_TEXTURE_2D);
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
gl.glTranslatef((float) mPosition.getX(), (float) mPosition.getY(), 0f);
float scaleFactor = (float) (2 * mRadius);
gl.glScalef(scaleFactor, scaleFactor, 0);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glColor4f (1f, 1.0f, 1, 1f);
gl.glFrontFace(GL10.GL_CW);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glPopMatrix();

after
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
put
gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);

How to set on texture on top of another texture in android using OPEN GL

I have been searching for this for the pass two days .I am developing an android game using Open GL in which there is a situation where i have to display two images at the same time, one should be the background image and second one is displayed depending on a condition.
I have displayed the background imgae using Open GL Texture property.But when i tried to display the second image by using texture first one is not displaying.Since i am dealing with multiple texture i have used a GLTexture class to manipulate the texture (http://tkcodesharing.blogspot.in/2008/05/working-with-textures-in-androids.html).Even then i am not able to display two images at the same time.
Here is some code :
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
glTextures= new GLTextures(gl,this.context);//class to manipulate textures
//adding image resources
this.glTextures.add(R.drawable.back);
this.glTextures.add(R.drawable.hand);
//loading texture
this.glTextures.loadTextures();
gl.glEnable(GL10.GL_TEXTURE_2D);
...
}
In onDrawFrame
gl.glClear(GL10.GL_COLOR_BUFFER_BIT|GL10.GL_DEPTH_BUFFER_BIT);
gl.glLoadIdentity();
gl.glTranslatef(0.0f, 0.0f, -3.5f);
glTextures.setTexture(R.drawable.back);//it will bind this particular texture for drawing
draw(gl);
if(condition == 1){
gl.glLoadIdentity();
gl.glTranslatef(0.0f, 1.0f, -7.0f);
glTextures.setTexture(R.drawable.hand);
drawSecond(gl);
}
////////////////////////////////////////////////////////
In draw code
public void draw(GL10 gl){
gl.glActiveTexture(GL10.GL_TEXTURE0);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glFrontFace(GL10.GL_CW);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length/3);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
}
public void drawSecond(GL10 gl){
gl.glActiveTexture(GL10.GL_TEXTURE1);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
//GLES20.glUniform1i(isShaked, 1);
gl.glFrontFace(GL10.GL_CW);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length/3);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
}

remove "gl.glActiveTexture(GL10.GL_TEXTURE0);" and gl.glActiveTexture(GL10.GL_TEXTURE1);
lines from the rendering code.
you use multiple texture units only if you need multi-texturing,
which is using multiple textures in one draw call.
just bind the first texture to the active texture unit (default to GL_TEXTURE0) and draw the first triangle strip, than bind the second texture (without changing the active texture unit GL_TEXTURE0) and draw the second triangle strip.

Android Opengl 2 shapes with different colors

I am a newbie with opengl on android. I am trying to draw two different shapes. Shape one has a texture while shape two is supposed to have a color, lets say green. When I run the application, the first shape gets its texture but has also the green color. The texture itself is turned greenish in color. Shape two is green as i wanted. Here is my draw method:
public void draw(GL10 gl) {
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//My first shape
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glPushMatrix();
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glPopMatrix();
//My second shape
gl.glPushMatrix();
//Setting the color green
gl.glColor4f(0.0f, 1.0f, 0.0f, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, locvertexBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, locvertices.length / 3);
gl.glPopMatrix();
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
}
Can anyone help me with this?

Try to put gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f); before drawing the first shape
OR
use gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE, GL10.GL_REPLACE);
after you bind the texture

TRIANGLE_FAN circle not drawn after draw squares with textures

UPDATE: Summary:
I can draw a circle using TRIANGLE_FAN and, separately, I also can draw two squares with bitmaps as textures. But the problem is when I draw the textures and then the circles. Circles aren't drawn.
I'm drawing two texturized squares (4 vertex each). Then I draw a circle using GL_TRIANGLE_FAN but it isn't being drawn correctly (see images).
When I draw the circles without the squares, it is drawn correctly.
Any ideas where could be the problem?
Please, ask for more information. Thanks
Adding some code that I think is important:
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glFrontFace(GL10.GL_CCW);
gl.glEnable(GL10.GL_CULL_FACE);
gl.glEnable(GL10.GL_BLEND);
gl.glCullFace(GL10.GL_BACK);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnable(GL10.GL_TEXTURE_2D);
}
public void onSurfaceChanged(GL10 gl, int w, int h) {
gl.glViewport(0, 0, width, height);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glOrthof(0, w, -0, h, -1, 1);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
}
public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
circle.draw(gl);
needle.draw(gl);
synchronized (tokens) {
for (Token d : tokens) {
d.draw(gl);
}
}
}
Update:
Some screenshots.
Without drawing circle and needle objects:
Drawing circle and needle:
(Look at those red lines where should be a circle)
The only change in the code between those images is commenting the lines
circle.draw(gl);
needle.draw(gl);
Token:
public void draw(GL10 gl) {
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glPushMatrix();
gl.glTranslatef(x, y, 0f);
gl.glScalef(radius, radius, 0f);
gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, nVertices+2);
gl.glPopMatrix();
}
Circle and Needle:
public void draw(GL10 gl) {
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
if (shouldLoadTexture) {
loadGLTexture(gl);
shouldLoadTexture = false;
}
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
gl.glBindTexture(GL10.GL_TEXTURE_2D, textureId);
gl.glPushMatrix();
gl.glTranslatef(x, y, 0f);
gl.glRotatef((float) angle, 0f, 0f, 1f);
angle += rotAngle;
if(angle+rotAngle > 360.0)
angle -= 360.0;
gl.glScalef(width, height, 0f);
gl.glDrawElements(GL10.GL_TRIANGLES, indices.length,
GL10.GL_UNSIGNED_SHORT, indexBuffer);
gl.glPopMatrix();
}
private void loadGLTexture(GL10 gl) {
int[] textures = new int[1];
gl.glGenTextures(1, textures, 0);
textureId = textures[0];
gl.glBindTexture(GL10.GL_TEXTURE_2D, textureId);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER,
GL10.GL_LINEAR);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER,
GL10.GL_LINEAR);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S,
GL10.GL_CLAMP_TO_EDGE);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T,
GL10.GL_REPEAT);
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);
}
Update:
Following what Arne says in the first answer, I changed:
public void draw(GL10 gl) {
//New line
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
if (shouldLoadTexture) {
loadGLTexture(gl);
shouldLoadTexture = false;
}
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
gl.glBindTexture(GL10.GL_TEXTURE_2D, textureId);
gl.glPushMatrix();
gl.glTranslatef(x, y, 0f);
gl.glRotatef((float) angle, 0f, 0f, 1f);
angle += rotAngle;
if(angle+rotAngle > 360.0)
angle -= 360.0;
gl.glScalef(width, height, 0f);
gl.glDrawElements(GL10.GL_TRIANGLES, indices.length,
GL10.GL_UNSIGNED_SHORT, indexBuffer);
gl.glPopMatrix();
//New line
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
}
Now I get no circle at all. Neither red line as in the second image.
Update:
When I don't load the texture of circle and needle (just commenting the call to loadTexture() ), I get this:
So the problem should be with the textures.

You enable texturing (by calling glEnable(GL_TEXTURE_2D)) at the beginning, but you don't provide your circles (tokens) any texture coordinates. As I suppose these shouldn't be textured, you should only enable texturing for the objects that are really textured and disable texturing again after drawing them, the same way you enable and disable the texCoord array in your updated code.

Try to disable GL_TEXTURE_COORD_ARRAY before drawing the circles with
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

Drawing text as textures on squares does not show anything

I'm new to OpenGL and I'm developing an Augmented-reality application for Android.
Until now, I was drawing white squares, perpendicular to the camera, pointing the user to the direction where a "Point of interest" would be.
Now, I'm trying to show some text into the squares.
I've read a lot and it seems that creating a texture with the text is the most direct and easiest approach, so I'm creating the textures as soon as I get data of the Points of interest and stick them to their squares. For that, I use bitmaps.
Let's see some code. Within my onDrawFrame method, I do something like this:
public void onDrawFrame(GL10 gl) {
// Get sensors matrix
...
//Clear Screen And Depth Buffer
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
// Load remapped matrix
gl.glMatrixMode(GL10.GL_MODELVIEW);
// List of Points of interest (modified when some data is downloaded)
synchronized (poiList) {
if(mNewData){ // True if new data has been dowloaded)
if(textures != null) // Delete old textures
gl.glDeleteTextures(textures.length, textures, 0);
textures = loadGLTexture(gl, soapPoiList.getPoiList());
mNewData = false;
}
int i = 0;
// Iterate the list
for (PointOfInterest c : poiList) {
gl.glLoadIdentity();
gl.glLoadMatrixf(remappedRotationMatrix, 0);
// Get bearing
...
// Place polygon in the right place
gl.glRotatef(-bearing, 0, 0, 1);
gl.glTranslatef(0, ICONS_SIZE_RATIO, 0);
// Actually draws the polygon with text
c.draw(gl, textures[i]);
i++;
}
}
}
Where loadGLTextures is:
protected int[] loadGLTexture(GL10 gl, List<PointOfInterest> l){
int res[] = new int[l.size()];
gl.glGenTextures(res.length, res, 0);
int i = 0;
for(PointOfInterest p : l) {
Bitmap bitmap = Bitmap.createBitmap(256, 256, Bitmap.Config.RGB_565);
bitmap.eraseColor(Color.BLACK);
Canvas canvas = new Canvas(bitmap);
Paint textPaint = new Paint();
textPaint.setTextSize(35);
textPaint.setFakeBoldText(true);
textPaint.setAntiAlias(true);
textPaint.setARGB(255, 255, 255, 255);
// Draw the text centered
canvas.drawText(Float.toString(p.getDinstanceToOrigin()) + " m.", 10,35, textPaint);
// Bind the texture to our array
gl.glBindTexture(GL10.GL_TEXTURE_2D, res[i]);
// Create Nearest Filtered Texture
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE);
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);
bitmap.recycle();
i++;
}
return res;
}
It basically creates a bitmap for each Point of Interest, and generate a texture with it. The texture will be applied over a white square later, as it is shown in this class:
public class PointOfInterest {
// MEMBERS ----------------------------------------------------------------
....
....
// OpenGL necessary variables
/** The buffer holding the vertices */
private FloatBuffer vertexBuffer;
/** The initial vertex definition */
private float vertices[] = {
-1.0f, 0.0f, -1.0f, //Bottom Left V1
-1.0f, 0.0f, 1.0f, //Top Left V2
1.0f, 0.0f, -1.0f, //Bottom Right V3
1.0f, 0.0f, 1.0f, //Top Right V4
};
private FloatBuffer textureBuffer;
private float texture[] = {
0.0f, 0.0f, // V1
1.0f, 0.0f, // V3
0.0f, 1.0f, // V2
1.0f, 1.0f // V4
};
// CONSTRUCTORS -----------------------------------------------------------
public PointOfInterest(Location originLocation){
currentLocation = originLocation;
mPoiLocation = new Location(LocationManager.GPS_PROVIDER);
ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
vertexBuffer = byteBuf.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
byteBuf = ByteBuffer.allocateDirect(texture.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
textureBuffer = byteBuf.asFloatBuffer();
textureBuffer.put(texture);
textureBuffer.position(0);
}
// PUBLIC METHODS ---------------------------------------------------------
public void draw(GL10 gl, int textureId){
// Bind the previously generated texture
gl.glBindTexture(GL10.GL_TEXTURE_2D, textureId);
// Point to our buffers
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
// set the colour for the square
//gl.glColor4f(0.0f, 0.1f, 0.0f, 0.5f);
//Set the face rotation
gl.glFrontFace(GL10.GL_CW);
//Point to our vertex buffer
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
//Draw the vertices as triangle strip
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
//Disable the client state before leaving
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
}
....
....
}
I have tried to map the texture as it is taught here and here with no success. I really don't know what to do to get some letters drawn on the squares and am really lost here... Maybe the text is being drawn on the other face of the square, maybe the textures are not being generated... I don't know.
Any kind of help would be very appreciated.

Okay, I had forgotten to enable texture mapping. You can do that within any method that uses the GL10 object. I prefer to do it within the draw method of my objects, so any other object is not affected by the texture. It's as simple as this (just changed 2 lines, the ones that say NEW!!):
public void draw(GL10 gl, int textureId){
gl.glEnable(GL10.GL_TEXTURE_2D); //NEW !!! Enable Texture Mapping
// Bind the previously generated texture
gl.glBindTexture(GL10.GL_TEXTURE_2D, textureId);
// Point to our buffers
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
// set the colour for the square
//gl.glColor4f(0.0f, 0.1f, 0.0f, 0.5f);
//Set the face rotation
gl.glFrontFace(GL10.GL_CW);
//Point to our vertex buffer
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
//Draw the vertices as triangle strip
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
//Disable the client state before leaving
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glDisable(GL10.GL_TEXTURE_2D); ////NEW !!! Disable texture mapping
}