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();
}
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
M4 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);
}
@Override
public 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();
}
@Override
public 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。