[置顶] 自己动手实现OpenGL-OpenGL原来如此简单（二）
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上篇对glViewPort的实现可见一斑。但是并没有提及其中的思路所在。本篇主要是简短地介绍一下WGL的实现思路。
由于OpenGL是一个状态机，既然是状态机，那么肯定有一系列的状态需要保存。OpenGL的状态对应的是功能的实现。我们这个简单的OpenGL不需要大而全的功能，那么需要哪些功能呢？
1.绘制一个立方体或者长方体。
2.长方体或者立方体可以旋转
3.用上面的长方体代表太阳，地球，月亮。模拟其运行周期。
好吧，就上面三个功能。那么说我们上面的三个功能需要保存哪些状态呢？其实就以下三个状态就够了：
1. 矩阵管理
2. 颜色管理
3. 绘制线框
这么简单！
好吧，那么就定义几个变量吧！
1.矩阵管理
矩阵管理，那么就必须有矩阵，那么我的矩阵是这样的：
/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.example.simulateopengl;import java.nio.FloatBuffer;import android.util.Log;/** * * A 4x4 float matrix * */public class M4 {public float[][] m = new float[4][4];public M4() {this.setIdentity();}@Overrideprotected Object clone() throws CloneNotSupportedException {// TODO Auto-generated method stubM4 other = new M4();for(int i = 0; i < 4; ++ i){for(int j = 0; j < 4; ++ j){other.m[i][j] = m[i][j];}}return other;}public M4(M4 other) {for (int i = 0; i < 4; i++) {for (int j = 0; j < 4; j++) {m[i][j] = other.m[i][j];}}}public void project(GLVertex src, GLVertex dest) {GLVertex srcCopy = new GLVertex(src.x, src.y, src.z, src.w);dest.x = (float)(srcCopy.x * m[0][0] + srcCopy.y * m[0][1] + srcCopy.z * m[0][2] + m[0][3]*srcCopy.w);dest.y = (float)(srcCopy.x * m[1][0] + srcCopy.y * m[1][1] + srcCopy.z * m[1][2] + m[1][3]*srcCopy.w);dest.z = (float)(srcCopy.x * m[2][0] + srcCopy.y * m[2][1] + srcCopy.z * m[2][2] + m[2][3]*srcCopy.w);dest.w = (float)(srcCopy.x * m[3][0] + srcCopy.y * m[3][1] + srcCopy.z * m[3][2] + m[3][3]*srcCopy.w);}public static void normalize(GLVertex verVertex){verVertex.x = verVertex.x/verVertex.w;verVertex.y = verVertex.y/verVertex.w;verVertex.z = verVertex.z/verVertex.w;verVertex.w = verVertex.w/verVertex.w;}public static M4 frustum(float left, float right, float bottom, float top, float near, float far){float[][] matrix = new float[4][4]; if (left == right) { throw new IllegalArgumentException("left == right"); } if (top == bottom) { throw new IllegalArgumentException("top == bottom"); } if (near == far) { throw new IllegalArgumentException("near == far"); } if (near <= 0.0f) { throw new IllegalArgumentException("near <= 0.0f"); } if (far <= 0.0f) { throw new IllegalArgumentException("far <= 0.0f"); } final float r_width = 1.0f / (right - left); final float r_height = 1.0f / (top - bottom); final float r_depth = 1.0f / (near - far); final float x = mul2f(near/(right - left));//00 final float y = mul2f(near * r_height);//11 final float A = (right + left) * r_width;//02 final float B = (top + bottom) * r_height;//12 final float C = (far + near) * r_depth;//22 final float D = mul2f(far * near * r_depth);//23 matrix[0][0] = x;matrix[0][1] = 0.0f;matrix[0][2] = A;matrix[0][3] = 0.0f; matrix[1][0] = 0.0f;matrix[1][1] = y; matrix[1][2] = B; matrix[1][3] = 0.0f; matrix[2][0] = 0.0f; matrix[2][1] = 0.0f; matrix[2][2] = C; matrix[2][3] = D; matrix[3][0] = 0.0f;matrix[3][2] = -1.0f; matrix[3][1] = 0.0f; matrix[3][3] = 0.0f; M4 m4 = new M4(); m4.m = matrix; return m4; }public static int toFixed(float x) {return Float.floatToIntBits(x);}public static float toFloatBytes(int fx){return Float.intBitsToFloat(fx);}static Float addExpf(Float v, int e) { int i = toFixed(v); if (i<<1 != 0) { i += (e)<<23; } return toFloatBytes(i);}static Float minusExpf(Float v, int e) { int i = toFixed(v); if (i<<1 != 0) { i -= (e)<<23; } return toFloatBytes(i);}static float mul2f(float v) { return addExpf(v, 1);}static float mul2fn(float v, int n) { return addExpf(v, n);}static float divide2fn(float v, int n) { return minusExpf(v, n);}public M4 multiply(M4 other) {M4 result = new M4();float[][] m1 = m;float[][] m2 = other.m;for (int i = 0; i < 4; i++) {for (int j = 0; j < 4; j++) {result.m[i][j] = m1[i][0]*m2[0][j] + m1[i][1]*m2[1][j] + m1[i][2]*m2[2][j] + m1[i][3]*m2[3][j];}}return result;}public void setIdentity() {for (int i = 0; i < 4; i++) {for (int j = 0; j < 4; j++) {m[i][j] = (i == j ? 1f : 0f);}}}public void setIntArray(int[] src){float[][] dst = new float[4][4];int i = 0, m, n;for(n = 0; n < dst[0].length; ++ n){for(m = 0; m < dst.length ; ++ m){dst[m][n] = Int2Float(src[i ++]);}}this.m = dst;}public float Int2Float(int fx){return divide2fn((float)fx, 16);}@Overridepublic String toString() {StringBuilder builder = new StringBuilder("[ ");for (int i = 0; i < 4; i++) {for (int j = 0; j < 4; j++) {builder.append(m[i][j]);builder.append(" ");}builder.append("\n ");}builder.append(" ]");return builder.toString();}@Overridepublic boolean equals(Object o) {//float[][] otherM = ((M4)o).m;Log.e("---", "wsgl: " + this.toString());Log.e("---", "systm gl: " + o.toString());return o.toString().equals(this.toString());} public static void translateM( float[][] m, float x, float y, float z) { for (int i=0 ; i<4 ; i++) { int mi = i; m[mi][3] += m[mi][0] * x + m[mi][1] * y + m[mi][2] * z; } }}然后，定义几个变量用来保存：
public static Stack<M4> mModelViewMatrixStack = new Stack<M4>(); public static Stack<M4> mProjectionMatrixStack = new Stack<M4>(); public static M4 mCurrentModelViewMatrix = new M4(); public static M4 mCurrentProjectionMatrix = new M4(); public static M4 mCurrentViewPortMatrix = new M4(); public static int mMatrixMode = GL10.GL_MODELVIEW;
2. 颜色管理
/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.example.simulateopengl;public class GLColor { public int red; public int green; public int blue; public int alpha; public GLColor(int red, int green, int blue, int alpha) { this.red = red; this.green = green; this.blue = blue; this.alpha = alpha; } public GLColor(int red, int green, int blue) { this.red = red; this.green = green; this.blue = blue; this.alpha = 0x10000; } @Override public boolean equals(Object other) { if (other instanceof GLColor) { GLColor color = (GLColor)other; return (red == color.red && green == color.green && blue == color.blue && alpha == color.alpha); } return false; }}public static GLColor mVertexColor = new GLColor(0, 0, 0);
3. 绘制管理。我们这里只按照三角形绘制：
/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.example.simulateopengl;import java.nio.IntBuffer;public class GLVertex { public double x; public double y; public double z; public double w = 1.0f; public short index; // index in vertex table GLColor color; GLVertex() { this.x = 0; this.y = 0; this.z = 0; this.w = 1.0f; this.index = -1; } GLVertex(double x, double y, double z, double w) { this.x = x; this.y = y; this.z = z; this.w = w; } @Override public boolean equals(Object other) { if (other instanceof GLVertex) { GLVertex v = (GLVertex)other; return (x == v.x && y == v.y && z == v.z); } return false; }// static public int toFixed(float x) {// return (int)(x * 65536.0f);// }// public void put(IntBuffer vertexBuffer, IntBuffer colorBuffer) {// vertexBuffer.put(toFixed(x));// vertexBuffer.put(toFixed(y));// vertexBuffer.put(toFixed(z));// if (color == null) {// colorBuffer.put(0);// colorBuffer.put(0);// colorBuffer.put(0);// colorBuffer.put(0);// } else {// colorBuffer.put(color.red);// colorBuffer.put(color.green);// colorBuffer.put(color.blue);// colorBuffer.put(color.alpha);// }// }//// public void update(IntBuffer vertexBuffer, M4 transform) {// // skip to location of vertex in mVertex buffer// vertexBuffer.position(index * 3);//// if (transform == null) {// vertexBuffer.put(toFixed(x));// vertexBuffer.put(toFixed(y));// vertexBuffer.put(toFixed(z));// } else {// GLVertex temp = new GLVertex();// transform.project(this, temp);// vertexBuffer.put(toFixed(temp.x));// vertexBuffer.put(toFixed(temp.y));// vertexBuffer.put(toFixed(temp.z));// }// }}定义个变量来保存顶点：
public static ArrayList<GLVertex> mVertexList = new ArrayList<GLVertex>();
好了，打工告成。
这就是实现一个地球，月亮，太阳模型的所有的东西都在这里。
总之，非常简单。后续博客将拿这8个变量来实现地球，月亮，太阳模型。
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