我成功地在 OpenGL ES 的正方形上映射了一个图像……但它旋转了 90 度。我是 OpenGL ES 的新手，想知道是否有人能指出它为什么会旋转。谢谢！
package se.jayway.opengl.tutorial;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;
import javax.microedition.khronos.opengles.GL10;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLUtils;
public class Square {
// Our vertices.
private float vertices[] = {
-1.0f, -1.0f, 0.0f, //Vertex 0
1.0f, -1.0f, 0.0f, //v1
-1.0f, 1.0f, 0.0f, //v2
1.0f, 1.0f, 0.0f, //v3
};
//Our texture.
private float texture[] = {
//Mapping coordinates for the vertices
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
};
// The order we like to connect them.
private byte indices[] = {
//Faces definition
0,1,3, 0,3,2, //Face front
};
// Our vertex buffer.
private FloatBuffer vertexBuffer;
// Our index buffer.
private ByteBuffer indexBuffer;
//texture buffer.
private FloatBuffer textureBuffer;
//Our texture pointer.
private int[] textures = new int[1];
public Square() {
ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
vertexBuffer = byteBuf.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
//
byteBuf = ByteBuffer.allocateDirect(texture.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
textureBuffer = byteBuf.asFloatBuffer();
textureBuffer.put(texture);
textureBuffer.position(0);
//
indexBuffer = ByteBuffer.allocateDirect(indices.length);
indexBuffer.put(indices);
indexBuffer.position(0);
}
/**
* This function draws our square on screen.
* @param gl
*/
public void draw(GL10 gl) {
//Bind our only previously generated texture in this case
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//Point to our buffers
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
//Set the face rotation
gl.glFrontFace(GL10.GL_CCW);
//Enable the vertex and texture state
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
//Draw the vertices as triangles, based on the Index Buffer information
gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer);
// Disable the vertices buffer.
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
//Disable the texture buffer.
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
// Disable face culling.
gl.glDisable(GL10.GL_CULL_FACE);
}
/**
* Load the textures
*
* @param gl - The GL Context
* @param context - The Activity context
*/
public void loadGLTexture(GL10 gl, Context context) {
//Get the texture from the Android resource directory
InputStream is = context.getResources().openRawResource(R.drawable.android);
Bitmap bitmap = null;
try {
//BitmapFactory is an Android graphics utility for images
bitmap = BitmapFactory.decodeStream(is);
} finally {
//Always clear and close
try {
is.close();
is = null;
} catch (IOException e) {
}
}
//Generate one texture pointer...
gl.glGenTextures(1, textures, 0);
//...and bind it to our array
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//Create Nearest Filtered Texture
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
//Different possible texture parameters, e.g. GL10.GL_CLAMP_TO_EDGE
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT);
//Use the Android GLUtils to specify a two-dimensional texture image from our bitmap
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);
//Clean up
bitmap.recycle();
}
}