I'm having trouble getting my Android opengl app to display a quad. Is there anything obviously wrong with this code?


public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();



float[] myverts = new float[]
{
-.77f, .58f,
.77f, .58f,
.77f, -.58f,
-.77f, -.58f
};

FloatBuffer[] fb = new FloatBuffer[1];
fb[0] = FloatBuffer.wrap(myverts);



float[] mytex = new float[]
{
0, 0,
1, 0,
1, 1,
0, 1
};


FloatBuffer[] tfb = new FloatBuffer[1];
tfb[0] = FloatBuffer.wrap(myverts);



gl.glTranslatef(0, 0, -5);

gl.glBindTexture(GL10.GL_TEXTURE_2D, texturesBuffer.get(0));
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

gl.glVertexPointer(2, GL10.GL_FLOAT, 0, fb[0]);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, tfb[0]);

gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, 4);




gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);


}

Quote:Original post by Nairb
Questions:
(1) What behavior are you observing? Is it that nothing at all is displaying? Or a white quad?
(2) Are you setting the projection matrix anywhere?
(3) Do you have face culling enabled? Have you tried disabling it?
(4) Where are you calling this method and what code is around it? I haven't looked into Android + GL in a while, but it's possible you have to worry about managing a graphics context.

1. I'm getting a black screen.

2. Yes.

GLU.gluPerspective(gl, 60.0f, 1.33f, .1f, 100.0f);

3. Yes, it was enabled, but disabling it didn't fix the issue.

4. Here's the other code in the file:




package ro.brite.android.nehe06;

import java.nio.FloatBuffer;
import java.nio.IntBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.content.Context;
import android.graphics.Bitmap;
import android.opengl.GLU;
import android.opengl.GLUtils;
import android.opengl.GLSurfaceView.Renderer;


public class GlRenderer implements Renderer {

private Context context;

public GlRenderer(Context context)
{
this.context = context;
}

private static float[][] cubeVertexCoords = new float[][] {
new float[] { // top
1, 1,-1,
-1, 1,-1,
-1, 1, 1,
1, 1, 1
},
new float[] { // bottom
1,-1, 1,
-1,-1, 1,
-1,-1,-1,
1,-1,-1
},
new float[] { // front
1, 1, 1,
-1, 1, 1,
-1,-1, 1,
1,-1, 1
},
new float[] { // back
1,-1,-1,
-1,-1,-1,
-1, 1,-1,
1, 1,-1
},
new float[] { // left
-1, 1, 1,
-1, 1,-1,
-1,-1,-1,
-1,-1, 1
},
new float[] { // right
1, 1,-1,
1, 1, 1,
1,-1, 1,
1,-1,-1
},
};

private static float[][] cubeTextureCoords = new float[][] {
new float[] { // top
1, 0,
1, 1,
0, 1,
0, 0
},
new float[] { // bottom
0, 0,
1, 0,
1, 1,
0, 1
},
new float[] { // front
1, 1,
0, 1,
0, 0,
1, 0
},
new float[] { // back
0, 1,
0, 0,
1, 0,
1, 1
},
new float[] { // left
1, 1,
0, 1,
0, 0,
1, 0
},
new float[] { // right
0, 1,
0, 0,
1, 0,
1, 1
},
};

private static FloatBuffer[] cubeVertexBfr;
private static FloatBuffer[] cubeTextureBfr;

private IntBuffer texturesBuffer;

private static float cubeRotX;
private static float cubeRotY;
private static float cubeRotZ;

static
{
cubeVertexBfr = new FloatBuffer[6];
cubeTextureBfr = new FloatBuffer[6];
for (int i = 0; i < 6; i++)
{
cubeVertexBfr = FloatBuffer.wrap(cubeVertexCoords);
cubeTextureBfr = FloatBuffer.wrap(cubeTextureCoords);
}
}

public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glClearColor(0, 0, 0, 0);

gl.glClearDepthf(1.0f);
gl.glEnable(GL10.GL_DEPTH_TEST);
gl.glDepthFunc(GL10.GL_LEQUAL);

// gl.glEnable(GL10.GL_CULL_FACE);
// gl.glCullFace(GL10.GL_BACK);

gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);

// create texture
gl.glEnable(GL10.GL_TEXTURE_2D);
texturesBuffer = IntBuffer.allocate(1);
gl.glGenTextures(1, texturesBuffer);
gl.glBindTexture(GL10.GL_TEXTURE_2D, texturesBuffer.get(0));

// setup texture parameters
gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE);
gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE);

// set the texture
Bitmap texture = Utils.getTextureFromBitmapResource(context, R.drawable.background);
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, texture, 0);
texture.recycle();
}

public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
gl.glDisable(GL10.GL_CULL_FACE);

// gl.
// glBegin(GL_QUADS);
// glTexCoord2f(0, 0);
// glVertex2f(-xdist, ydist);
// glTexCoord2f(1, 0);
// glVertex2f(xdist, ydist);
// glTexCoord2f(1, 1);
// glVertex2f(xdist, -ydist);
// glTexCoord2f(0, 1);
// glVertex2f(-xdist, -ydist);
// glEnd();
//

float[] myverts = new float[]
{
-.77f, .58f,
.77f, .58f,
.77f, -.58f,
-.77f, -.58f
};

FloatBuffer[] fb = new FloatBuffer[1];
fb[0] = FloatBuffer.wrap(myverts);



float[] mytex = new float[]
{
0, 0,
1, 0,
1, 1,
0, 1
};


FloatBuffer[] tfb = new FloatBuffer[1];
tfb[0] = FloatBuffer.wrap(myverts);



// float xdist = .77;
// float ydist = .58;
//
// glColor3f(1, 1, 1);
// glEnable(GL_TEXTURE_2D);
// glBindTexture(GL_TEXTURE_2D, backtexture);
// // background
// glBegin(GL_QUADS);
// glTexCoord2f(0, 0);
// glVertex2f(-xdist, ydist);
// glTexCoord2f(1, 0);
// glVertex2f(xdist, ydist);
// glTexCoord2f(1, 1);
// glVertex2f(xdist, -ydist);
// glTexCoord2f(0, 1);
// glVertex2f(-xdist, -ydist);
// glEnd();


// draw cube

gl.glTranslatef(0, 0, -5);
// gl.glRotatef(cubeRotX, 1, 0, 0);
// gl.glRotatef(cubeRotY, 0, 1, 0);
// gl.glRotatef(cubeRotZ, 0, 0, 1);
//
gl.glBindTexture(GL10.GL_TEXTURE_2D, texturesBuffer.get(0));
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

gl.glVertexPointer(2, GL10.GL_FLOAT, 0, fb[0]);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, tfb[0]);

gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, 4);



// for (int i = 0; i < 6; i++) // draw each face
// {
// gl.glVertexPointer(3, GL10.GL_FLOAT, 0, cubeVertexBfr);
// gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, cubeTextureBfr);
// gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, 4);
// }
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

// update rotations
cubeRotX += 1.2f;
cubeRotY += 0.8f;
cubeRotZ += 0.6f;
}

public void onSurfaceChanged(GL10 gl, int width, int height) {
// avoid division by zero
if (height == 0) height = 1;
// draw on the entire screen
gl.glViewport(0, 0, width, height);
// setup projection matrix
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
// GLU.gluPerspective(gl, 45.0f, (float)width / (float)height, 1.0f, 100.0f);
GLU.gluPerspective(gl, 45.0f, (float)1.0 / (float)1.0, 1.0f, 100.0f);
//gluPerspective(60.0f, 1.33, .1, 100.0f);
GLU.gluPerspective(gl, 60.0f, 1.33f, .1f, 100.0f);
}

}