Develop Reference

Libgdx: Framebuffer for "Fog of War"-Effect

I am writing a RTS Game for Android and I want the "Fog of War" effect on the player's units. This effect means that only a "circle" around each unit shows the background map while on places where no player unit is located, the screen should be black. I don't want to use shaders.
I have a first version of it working. What I am doing is to render the map to the default framebuffer, then I have a second Framebuffer (similar to light technics) which is completely black. Where the units of the players are, I then batch-draw a texture which is completely transparent and has a white circle with blurred edges in its middle.
Finally I draw the second (light) FrameBuffer's colorTexture over the first one using Gdx.gl.glBlendFunc(GL20.GL_DST_COLOR, GL20.GL_ZERO);
The visual effect now is that indeed the whole map is black and a circle around my units is visible - but a lot of white color is added.
The reason is pretty clear as I drew the light textures for the units like this:
lightBuffer.begin();
Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE);
Gdx.gl.glEnable(GL20.GL_BLEND);
Gdx.gl.glClearColor(0.1f, 0.1f, 0.1f, 1f);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.setColor(1f, 1f, 1f, 1f);
for (RTSTroopAction i : unitList) {
batch.draw(lightSprite, i.getX() + (i.getWidth() / 2) - 230, i.getY() + (i.getHeight() / 2) - 230, 460, 460); //, 0, 0, lightSprite.getWidth(), lightSprite.getHeight(), false, true);
}
batch.end();
lightBuffer.end();
However, I don't want the "white stuff" on the original texture, I just want the original background shine through. How can I achieve that ?
I think it's playing around with the blendFuncs, but I was not able to figure out which values to use yet.

Thanks to Tenfour04 pointing into the right direction, I was able to find the solution. First of all, the problem is not directly within batch.end();. The problem is, that indeed a sprite batch maintains its own blendFunc Settings. These get applied when flush(); is called. (end() calls it also ).
However the batch is also calling flush when it draws a TextureRegion that is bound to a different texture than the one used in the previous draw() call.
So in my original code: whatever blendFunc I had set was always overridden when I called batch.draw(lightBuffer,...). The solution is to use the spritebatch's blendFunc and not the Gdx.gl.blendFunc.
The total working code finally looks like this:
lightBuffer.begin();
Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);
Gdx.gl.glEnable(GL20.GL_BLEND);
// start rendering to the lightBuffer
// set the ambient color values, this is the "global" light of your scene
Gdx.gl.glClearColor(0.1f, 0.1f, 0.1f, 1f);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
// start rendering the lights
batch.setProjectionMatrix(camera.combined);
batch.begin();
// set the color of your light (red,green,blue,alpha values)
batch.setColor(1f, 1f, 1f, 1f);
for (RTSTroopAction i : unitList) {
if (i.getOwnerId() == game.getCallback().getPlayerId()) {
batch.draw(lightSprite, i.getX() + (i.getWidth() / 2) - 230, i.getY() + (i.getHeight() / 2) - 230, 460, 460); //, 0, 0, lightSprite.getWidth(), lightSprite.getHeight(), false, true);
}
}
batch.end();
lightBuffer.end();
// now we render the lightBuffer to the default "frame buffer"
// with the right blending !
Gdx.gl.glEnable(GL20.GL_BLEND);
Gdx.gl.glBlendFunc(GL20.GL_ZERO, GL20.GL_SRC_COLOR);
batch.setProjectionMatrix(getStage().getCamera().combined);
batch.enableBlending();
batch.setBlendFunction(GL20.GL_ZERO, GL20.GL_SRC_COLOR);
batch.begin();
Gdx.gl.glEnable(GL20.GL_BLEND);
Gdx.gl.glBlendFunc(GL20.GL_ZERO, GL20.GL_SRC_COLOR);
batch.draw(lightBufferRegion,0, 0, getStage().getWidth(), getStage().getHeight());
batch.end();
batch.setBlendFunction(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);

Android - high fps drop with OpenGL ES 1.1

I am trying to make a simple 2D game. I have noticed that the onDrawFrame() function is called in 60 FPS with vsync. However for some reason on older devices if rendering time exceeds 1ms then it will skip a frame every few frame and the animation doesn't look smooth at all. And I am talking about devices that aren't too old...
90% of the drawing code looks like this:
gl.glBindTexture(GL11.GL_TEXTURE_2D, MainProgram.glSurfaceView.renderer.ResourceIdToTexture(R.drawable.tank));
gl.glFrontFace(GL11.GL_CW);
gl.glVertexPointer(3, GL11.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL11.GL_FLOAT, 0, tankTextureBuffer);
float[] glCoords = World.WorldCoordsToGLCoords(tank.GetPosition().PosX(), tank.GetPosition().PosY());
float[] glDims = {0.025f, 0.025f};
gl.glPushMatrix();
gl.glTranslatef(glCoords[0], glCoords[1]+glDims[1], -1.0f);
gl.glScalef(glDims[0], glDims[1], 1.0f);
float[] tc = tank.GetOwner().GetColor().asFloatArray();
gl.glColor4f(tc[0],tc[1],tc[2],tc[3]);
gl.glDrawArrays(GL11.GL_TRIANGLE_STRIP, 0, vertex.length / 3);
gl.glColor4f(1f, 1f, 1f, 1f);
gl.glPopMatrix();
Still, it took 1 millisecond to process all of the drawings to the screen and I have noticed that the FPS (I have measured the number of timer per second the surfaceView.drawFrame is called) drops from 60 to around 30 and it looks almost disgusting.
How do other games have such smooth animations even on the oldest devices?
And how do I achieve this with GLES11?

android opengl rendering garbage

I've been doing some simple shaders and Im encountering an error that happens randomly, when I start rendering my scene, sometimes the mesh is rendered with extra vectors, and if I kill the activity and then I open the same activity it renders sometimes without the extra vectors.
My guesses are that the memory on the GPU is not completely wiped out when I kill the activity. Whats more weird is that these extra polygons are rendered sometimes using my shader logic and other times they render as if they were filled with random squares.
Im going all crazy I've reviewed all the code, from where I read the obj, to where I set the vertex attributes, if you have been seen this before please let me know. BTW I'm using a motorola milestone with android 2.1.
This is the code related where I create a simple triangle and set the attributes of the vertices:
//This is where I create the mesh
mMesh = new Mesh();
mMesh.setVertices(new float[]{-0.5f, 0f, 0.5f,
0.5f, 0f, -0.5f,
-0.5f, 0f, -0.5f});
ArrayList<VertexAttribute> attributes = new ArrayList<VertexAttribute>();
attributes.add(new VertexAttribute(Usage.Position, 3, ProgramShader.POSITION_ATTRIBUTE));
VertexAttributes vertexAttributes = new VertexAttributes(attributes.toArray(new VertexAttribute[attributes.size()]));
mMesh.setVertexAttributes(vertexAttributes);
...
...
.......
//This is where I send the mesh to opengl
for(VertexAttribute attr :mVertexAttributes.getAttributes().values()){
mVertexBuffer.position(attr.offset);
int handler = shader.getHandler(attr.alias);
if(handler != -1){
try{
GLES20.glVertexAttribPointer(handler, attr.numComponents, GLES20.GL_FLOAT, false, mVertexAttributes.vertexSize, mVertexBuffer);
GLES20.glEnableVertexAttribArray(handler);
}catch (RuntimeException e) {
Log.d("CG", attr.alias);
throw e;
}
}
}
//(length = 3 for a triangle)
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, length);
Here are some screenshots for you to see the issue:
Screenshots
Also here is a link to a video I took when I run the app on the phone.
Video

So... I found the problem it was a really dumb thing I was doing,
//on this line I was sending length, where length was
//the length of the vertices for the triangle it was "9" (x,y,z for each vertex)
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, length);
//I had to divide that by the number of components for each vertex
//so when the vertex only has position attributes (x,y,z) is divided by 3
//when you have more i.e. normals it will be divided by 6 (x,y,z, normalX, normalY, normalZ)
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, length/mVertexAttributes.vertexNumComponents);
I hope this helps others.

Android -- OpenGL doesn't display w/ emulator?

When I run my program on an emulator, it displays an ImageView splash screen, then a black screen for the remainder of the application, which uses GLSurfaceViews. The OGL runs well on my phone. I have tested the program on two computers (low and high performance) and neither displays the GLSurfaceViews. I have also tested the emulator using some of the OGL demos from the Google apidemos interweb site and the demos don't display on either computer. My program uses OGL es 1.1, however I have also tested using OGL es 1.0 to no avail. How might I display ogl on an emulator? Thanks.
Here's an example of some simple square rendering code that doesn't work on the emulator
public void onDrawFrame(GL10 gl) {
//This works
gl.glClearColor(_red, _green, _blue, 1.0f);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
//This doesn't
float vertices[] = { .5f, .5f, 0, .5f, -.5f, 0, -.5f, .5f, 0, -.5f, -.5f, 0 };
FloatBuffer vertexSquareBuffer = ByteBuffer.allocateDirect(4 * 3 * 4)
.order(ByteOrder.nativeOrder()).asFloatBuffer();
vertexSquareBuffer.put(vertices);
vertexSquareBuffer.position(0);
gl.glColor4f(1, 1, 0, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexSquareBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0,4);
}

Well there are some possibilities. Firstly lets see if something that should work, does work on your emulator. Can you please go here and try this tutorial and run it through your emulator: http://www.droidnova.com/android-3d-game-tutorial-part-i,312.html (Do this bit first)
That way we know if the problem is with your code or the emulator.
After that you might need to look to see if there are all the required shared object libraries present.
Let me know in the comments how you go.

glDrawArrays works in vm, crashes on phone

I am drawing a line in opengl es from the Android NDK. I have been developing on the VM's and just recently tried my application on a phone. The application runs fine on the vm's. A line is drawn. However, on a motorola droid, the application just crashes, and on a HTC incredible it just shows a black screen. I have verified that the number being passed to the function are correct. The application haults on the glDrawArray(GL_LINES, 0, 2) call. The whole function looks like this:
void drawLine(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2, GLfloat * color)
{
GLfloat vVertices[] =
{x1, y1,
x2, y2};
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glColor4f(color[0],color[1],color[2],color[3]);
glVertexPointer(2, GL_FLOAT, 0, vVertices);
glDrawArrays(GL_LINES, 0, 2);
__android_log_write(ANDROID_LOG_ERROR,"to mama","You drew arrays");
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
}
and the call to it looks like this:
drawLine(0.0f,0.0f,1.0f,0.0f,colorx);/*x is green*/
I can try drawelements next, but there is not reason draw arrays should not work (as far as i know).

You're enabling the color array (glEnableClientState(GL_COLOR_ARRAY)) without actually setting setting the glColorPointer().
Either set the color pointer or don't enable the color array.