4 个顶点 * 6 个面超出了您的需要。实际上它不会有效率。您拥有的导出顶点已使用索引进行了优化。使用 Opengl-es,您可以指向从哪里获取顶点(数组),然后使用它们在另一个数组中的索引绘制顶点。结果你得到 8 个顶点而不是可能的 24 个顶点,你需要更少的内存来存储。所以效率是 16/24 * 100%。想象一下,您将有一个具有 1000 个顶点的模型。
顶点索引意味着在另一个具有适当偏移量的数组中,GPU 将获得一个顶点 (size_of_vertex(3 floats)*index) 和适当的 UV 坐标偏移量 (size_of_UVcoord(2 floats)*index)
此代码适用于 opengl ES 2.0,但您可以了解一下:
GLES20.glUseProgram(programTextured);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTextureID);
sqTex.getVertexBuffer().position(sqTex.VERT_OFFSET);
GLES20.glVertexAttribPointer(GLES20.glGetAttribLocation(programTextured, "aPosition") 3, GLES20.GL_FLOAT, false, 5 * 4, sqTex.getVertexBuffer()); GLES20.glEnableVertexAttribArray(GLES20.glGetAttribLocation(programTextured, "aPosition"));
sqTex.getVertexBuffer().position(sqTex.TEXT_OFFSET);
GLES20.glVertexAttribPointer(
GLES20.glGetAttribLocation(programTextured, "aTextureCoord"), 2,
GLES20.GL_FLOAT, false, 5 * 4, sqTex.getVertexBuffer());
GLES20.glDrawElements(GLES20.GL_TRIANGLES, 6, GLES20.GL_UNSIGNED_SHORT, sqTex.getIndexBuffer());
sqTEx 是 TexturedSquare 的一个实例:
public class TexturedSquare {
// private float[] vertices=new float[4];
float vertices[] = { -1.0f, -1.0f, 0.0f,0.0f,0.0f, // 0, Top Left //x,y,z,u,v
1.0f, -1.0f, 0.0f,0.0f,1.0f, // 1, Bottom Left
1.0f, 1.0f, 0.0f,1.0f,1.0f, // 2, Bottom Right
-1.0f, 1.0f, 0.0f,1.0f,0.0f, // 3, Top Right
};
public static int VERT_OFFSET=0;
public static int TEXT_OFFSET=3;
short[] indices = { 0, 1, 2, 2, 3, 0 };;
// Our vertex buffer.
private FloatBuffer vertexBuffer;
// Our index buffer.
private ShortBuffer indexBuffer;
public TexturedSquare()
{
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
vbb.order(ByteOrder.nativeOrder());
vertexBuffer = vbb.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
// short is 2 bytes, therefore we multiply the number if
// vertices with 2.
ByteBuffer ibb = ByteBuffer.allocateDirect(indices.length * 2);
ibb.order(ByteOrder.nativeOrder());
indexBuffer = ibb.asShortBuffer();
indexBuffer.put(indices);
indexBuffer.position(0);
}
FloatBuffer getVertexBuffer(){
return vertexBuffer;
}
ShortBuffer getIndexBuffer(){
return indexBuffer;
}
}