So I’m in the process of writing an Android app that will render 3D urban cities created with CityGML software. After feeding it through a parser to get just the vertice coordinates, I plug that array into my function (which I incorrectly assumed would just “work”).
Because the scenes are large, there are going to be lots of coordinates/vertices, so I decided to use glDrawArrays, because I don’t have a list of indices.
Question 1: Am I even close?
Question 2: Is there a mathematical function that I’m missing that generates the indices array?
Question 3: Should I be doing it differently, and if so, how?
Here’s a video showing what’s going wrong.
http://www.youtube.com/watch?v=1Iu0YxKK2pU&feature=youtube_gdata_player
Here’s the portion of my code that I think it wrong. The current vertex array I’m using is a basic cube I pulled off the interwebs.
package com.android.vortex;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
import android.opengl.GLSurfaceView;
public class VortexRenderer implements GLSurfaceView.Renderer {
private FloatBuffer _vertexBuffer;
private int _nrOfVertices = 0;
private float _xAngle;
private float _yAngle;
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glEnable(GL10.GL_CULL_FACE);
gl.glFrontFace(GL10.GL_CCW);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
initShape();
}
public void onSurfaceChanged(GL10 gl, int w, int h) {
gl.glViewport(0, 0, w, h);
}
public void setXAngle(float angle) {
_xAngle = angle;
}
public float getXAngle() {
return _xAngle;
}
public void setYAngle(float angle) {
_yAngle = angle;
}
public float getYAngle() {
return _yAngle;
}
public void onDrawFrame(GL10 gl) {
gl.glLoadIdentity();
gl.glRotatef(_xAngle, 1f, 0f, 0f);
gl.glRotatef(_yAngle, 0f, 1f, 0f);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glOrthof(-2.0f, 2.0f, -2.0f, 2.0f, -2.0f, 2.0f);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glRotatef(3.0f, 3.0f, 0.0f, 1.0f);
gl.glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glEnable(GL10.GL_LIGHTING);
gl.glEnable(GL10.GL_LIGHT0);
for(int i = 0; i<=_nrOfVertices; i+=3) {
gl.glDrawArrays(GL10.GL_TRIANGLES, i, 3);
}
}
private void initShape() {
float[] coords = {
1.0f,1.0f,1.0f,-1.0f,1.0f,1.0f,-1.0f,-1.0f,1.0f,1.0f,-1.0f,1.0f,
1.0f,1.0f,1.0f,1.0f,-1.0f,1.0f,1.0f,-1.0f,-1.0f,1.0f,1.0f,-1.0f,
1.0f,1.0f,1.0f,1.0f,1.0f,-1.0f,-1.0f,1.0f,-1.0f,-1.0f,1.0f,1.0f,
-1.0f,1.0f,1.0f,-1.0f,1.0f,-1.0f,-1.0f,-1.0f,-1.0f,-1.0f,-1.0f,1.0f,
-1.0f,-1.0f,-1.0f,1.0f,-1.0f,-1.0f,1.0f,-1.0f,1.0f,-1.0f,-1.0f,1.0f,
1.0f,-1.0f,-1.0f,-1.0f,-1.0f,-1.0f,-1.0f,1.0f,-1.0f,1.0f,1.0f,-1.0f
};
_nrOfVertices = coords.length;
ByteBuffer vbb = ByteBuffer.allocateDirect(coords.length * 4);
vbb.order(ByteOrder.nativeOrder());
_vertexBuffer = vbb.asFloatBuffer();
_vertexBuffer.put(coords);
_vertexBuffer.position(0);
}
}