[英]Problem drawing a sphere in OPENGL ES
我一直在嘗試用OpenGL ES創建自己的球體,我按照這里描述的數學運算http://www.math.montana.edu/frankw/ccp/multiworld/multipleIVP/spherical/learn.htm
然而,當我繪制球體(只是頂點)時,只繪制了一半球體。 能否請您指出我在下面給出的代碼中的確切問題:
public class Sphere {
static private FloatBuffer sphereVertex;
static private FloatBuffer sphereNormal;
static float sphere_parms[]=new float[3];
double mRaduis;
double mStep;
float mVertices[];
private static double DEG = Math.PI/180;
int mPoints;
/**
* The value of step will define the size of each facet as well as the number of facets
*
* @param radius
* @param step
*/
public Sphere( float radius, double step) {
this.mRaduis = radius;
this.mStep = step;
sphereVertex = FloatBuffer.allocate(40000);
mPoints = build();
Log.d("ALIS CHECK!!!!!!", " COUNT:" + mPoints);
}
public void draw(GL10 gl) {
gl.glFrontFace(GL10.GL_CW);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, sphereVertex);
gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
gl.glDrawArrays(GL10.GL_POINTS, 0, mPoints);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
}
private int build() {
/**
* x = p * sin(phi) * cos(theta)
* y = p * sin(phi) * sin(theta)
* z = p * cos(phi)
*/
double dTheta = mStep * DEG;
double dPhi = dTheta;
int points = 0;
for(double phi = -(Math.PI/2); phi <= Math.PI/2; phi+=dPhi) {
//for each stage calculating the slices
for(double theta = 0.0; theta <= (Math.PI * 2); theta+=dTheta) {
sphereVertex.put((float) (mRaduis * Math.sin(phi) * Math.cos(theta)) );
sphereVertex.put((float) (mRaduis * Math.sin(phi) * Math.sin(theta)) );
sphereVertex.put((float) (mRaduis * Math.cos(phi)) );
points++;
}
}
sphereVertex.position(0);
return points;
}
}
這里還有我的渲染器類:
/**
* These values are used to rotate the image by a certain value
*/
private float xRot;
private float yRot;
public void setxRot(float xRot) {
this.xRot += xRot;
}
public void setyRot(float yRot) {
this.yRot += yRot;
}
public GLViewRenderer(Context ctx) {
//initialize our 3D triangle here
mSphere = new Sphere(1, 25);
//Initializing the rate counter object
//This will help us in calculating the frames per second
fpsCalculator = new RateCounter(TAG);
fpsCalculator.start();
}
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
//initialize all the things required for openGL configurations
gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);
}
public void onDrawFrame(GL10 gl) {
if(fpsCalculator != null)
fpsCalculator.countOnce();
//write the drawing code needed
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glLoadIdentity();
/**
* Change this value in z if you want to see the image zoomed in
*/
gl.glTranslatef(0.0f, 0.0f, -5.0f);
gl.glRotatef(xRot, 0.0f, 1.0f, 0.0f);
gl.glRotatef(yRot, 1.0f, 0.0f, 0.0f);
mSphere.draw(gl);
}
public void onSurfaceChanged(GL10 gl, int width, int height) {
if(height == 0) {
height = 1;
}
gl.glViewport(0, 0, width, height);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
//Calculate The Aspect Ratio Of The Window
GLU.gluPerspective(gl, 45.0f, (float)width / (float)height, 0.1f, 100.0f);
gl.glMatrixMode(GL10.GL_MODELVIEW); //Select The Modelview Matrix
gl.glLoadIdentity(); //Reset The Modelview Matrix
}
/**
* Used to stop the FPS counter
*/
public void pause() {
if(fpsCalculator != null)
fpsCalculator.stop();
}
}
我真的很感激這方面的一些幫助。
PS:我嘗試將CW改為CCW仍然沒有運氣謝謝
改變這個
for(double phi = -(Math.PI/2); phi <= Math.PI/2; phi+=dPhi)
對此
for(double phi = -(Math.PI); phi <= Math.PI; phi+=dPhi)
實際上,改變
for(double phi = -(Math.PI/2); phi <= Math.PI/2; phi+=dPhi)
至
for(double phi = -(Math.PI); phi <= 0; phi+=dPhi)
足夠。 使用從 - (Math.PI)到+(Math.PI)的phi,你可以轉動360度並將每個點計數兩次。 你也可以這樣做:
for(double phi = -(Math.PI); phi <= Math.PI; phi+=dPhi) {
for(double theta = 0.0; theta <= (Math.PI); theta+=dTheta) {
...
}
}
避免計數兩次。
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