Source code is below.
Robert Green provides some helpful information, for which I am
thankful.
However, I am not clear on two of the points.
I currently have the situation where no lines at all show on the
emulator (the background color does) and things work perfectly on the
G1.
On Aug 2, 11:26 am, Robert Green <rbgrn....@gmail.com> wrote:
....
> 1) You are in a native resolution to the screen you're rendering on
> (turn all the density and screen-size stuff on in the manifest to
> avoid compat mode)
Are these the attributes on the "support-screens" tag? I did not have
that tag, but adding it and turning on all the attributes in the check-
boxes did not solve the problem.
> 2) You draw the lines centered on their pixel, so they look a half
> pixel off.
> -- To draw a horizontal line across the top row of pixels, you need to
> make the line with 1.0f and have y be 0.5f (because it will draw from
> 0 to 1 that way)
I am drawing in fixed point projection(?) space, so the relationship
of the lines to pixels is not clear. Also, I don't want to have to
redraw the lines when the scale changes - I want to be able to zoom
and pan easily. Is there a way to achieve that and have the lines
show?
> 3) Make sure you don't have any z-fighting. Drawing 2 things on the
> exact same plane with depth-test turned on causes bad results on many
> opengl implementations.
Depth test turned off. I'm doing 2D only, so I think I'm clear there.
Again, thanks for the help.
============ CODE SNIPS ==============
----- Create glSurfaceView -------
private GLSurfaceView makeGLSurfaceView(GLSurfaceView.Renderer
renderer, Context context) {
GLSurfaceView view = new GLSurfaceView(context);
view.setDebugFlags(GLSurfaceView.DEBUG_CHECK_GL_ERROR |
GLSurfaceView.DEBUG_LOG_GL_CALLS);
view.setEGLConfigChooser(false);
if ( renderer != null ) {
view.setRenderer(renderer);
view.setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
}
view.getHolder().setFormat(PixelFormat.OPAQUE);
return view;
} // make gl surface view
------------ onDrawFrame ----------
// Everything stuffed into onDrawFrame to make it easy to read on
forum
@Override
public void onDrawFrame(GL10 gl) {
gl.glClearColor(0,0,.2f, 1f);
gl.glDisable(GL10.GL_CULL_FACE);
gl.glShadeModel(GL10.GL_FLAT);
gl.glDisable(GL10.GL_DEPTH_TEST);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glViewport(0, 0, MyApp._width, MyApp._height);
gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
gl.glEnable(GL10.GL_LINE_SMOOTH);
gl.glDisableClientState(GL10.GL_COLOR_ARRAY);
_hgt2width = (float) MyApp._width / MyApp._height;
gl.glOrthof(-_hgt2width, _hgt2width, -1, 1, 1, -1);
gl.glScalef(1, _hgt2width, 1);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
float lscale = .002f*MyApp._curScale;
gl.glPushMatrix();
gl.glColor4f(1f, 1f, 0f, 1f);
gl.glTranslatef(.375f, .5f, 0f);
gl.glScalef( lscale, lscale, 1f);
gl.glVertexPointer(2, GL10.GL_FIXED, 0, _lineVertices);
gl.glLineWidthx(0x1);
drawArrays(gl);
gl.glPopMatrix();
gl.glPushMatrix();
gl.glColor4f(1f, 1f, 1f, 1.0f);
gl.glScalef( lscale*8, lscale*8, 1f);
gl.glVertexPointer(2, GL10.GL_FIXED, 0, _lineVertices);
gl.glLineWidthx(0x1);
drawArrays(gl);
gl.glPopMatrix();
}
void drawArrays(GL10 gl) {
gl.glDrawArrays(GL10.GL_LINE_STRIP, 0, 5); //small square
gl.glDrawArrays(GL10.GL_LINE_STRIP, 5, 5); //medium square
gl.glDrawArrays(GL10.GL_LINE_STRIP, 10, 5);//large square
gl.glDrawArrays(GL10.GL_LINE_STRIP, 15, 2);//x axis
gl.glDrawArrays(GL10.GL_LINE_STRIP, 17, 2);//y axis
gl.glDrawArrays(GL10.GL_LINE_STRIP, 19, 2);//X half
gl.glDrawArrays(GL10.GL_LINE_STRIP, 21, 2);//X half
}
void makeLines() {
int hlf = 0x08000;
int one = 0x10000+hlf;
int sml = one/8;
int ten = one;
int big = 0x40000000;
Log.d("===jrm", String.format("one:%x big:%x", one, big));
int vertices[] = {
-sml , sml, //0 start square - scale 1/10
sml , sml, //1
sml , -sml, //2
-sml , -sml, //3
-sml , sml, //4
-one , one, //5 start square - scale 1
one , one, //6
one , -one, //7
-one , -one, //8
-one , one, //9
-ten , ten, //10 start square - scale 10
ten , ten, //11
ten , -ten, //12
-ten , -ten, //13
-ten , ten, //14
-big , 0, //15 start coord axes over huge area
big , 0, //16
0 , big, //17
0 , -big, //18
-big , -big, //19 start X over huge dimensions
big , big, //20
-big , big, //21
big , -big, //22
ten , one // BUT? Without this line, blows up
if openGL debug is enabled
};
this.numLines = vertices.length/2;
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length*4);
vbb.order(ByteOrder.nativeOrder());
_lineVertices = vbb.asIntBuffer();
_lineVertices.put(vertices);
_lineVertices.position(0);
}
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