1 前言
????????光照元素主要有环境光（ambient）、漫反射光（diffuse）、镜面反射光（specular），光照模型主要有冯氏模型和 Blinn 改进的冯氏模型，两者区别在与镜面反射光的计算，冯氏模型根据反向量和观察向量计算镜面反射光，Blinn 改进的冯氏模型根据半向量和法向量计算镜面反射光。
????????模型合成颜色：finalColor = (ambient + diffuse + specular) · modelColor
- 环境光：ambient =?ambientStrength · ambientColor
- 漫反射光：diffuse = cos(α)· diffuseStrength · lightColor
- 镜面反射光：specular = pow(cos(β), μ)· specularStrength · lightColor
?????????读者如果对 OpenGL ES 不太熟悉，请回顾以下内容：
?????本文完整代码资源见→Blinn改进的冯氏光照模型。
????????项目目录如下：?
2 案例
????????MainActivity.java
package com.zhyan8.light.activity;
import android.opengl.GLSurfaceView;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import com.zhyan8.light.opengl.MyGLSurfaceView;
import com.zhyan8.light.opengl.MyRender;
public class MainActivity extends AppCompatActivity {
private GLSurfaceView mGlSurfaceView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mGlSurfaceView = new MyGLSurfaceView(this);
setContentView(mGlSurfaceView);
mGlSurfaceView.setRenderer(new MyRender(getResources()));
}
@Override
protected void onResume() {
super.onResume();
mGlSurfaceView.onResume();
}
@Override
protected void onPause() {
super.onPause();
mGlSurfaceView.onPause();
}
}????????MyGLSurfaceView.java
package com.zhyan8.light.opengl;
import android.content.Context;
import android.opengl.GLSurfaceView;
import android.util.AttributeSet;
public class MyGLSurfaceView extends GLSurfaceView {
public MyGLSurfaceView(Context context) {
super(context);
setEGLContextClientVersion(3);
}
public MyGLSurfaceView(Context context, AttributeSet attrs) {
super(context, attrs);
setEGLContextClientVersion(3);
}
}????????MyRender.java
package com.zhyan8.light.opengl;
import android.content.res.Resources;
import android.opengl.GLES30;
import android.opengl.GLSurfaceView;
import com.zhyan8.light.model.Model;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
public class MyRender implements GLSurfaceView.Renderer {
private Model mModel;
public MyRender(Resources resources) {
mModel = new Model(resources);
}
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig eglConfig) {
//设置背景颜色
GLES30.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
//启动深度测试
GLES30.glEnable(GLES30.GL_DEPTH_TEST);
//创建程序id
mModel.onModelCreate();
}
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
//设置视图窗口
GLES30.glViewport(0, 0, width, height);
mModel.onModelChange(width, height);
}
@Override
public void onDrawFrame(GL10 gl) {
//将颜色缓冲区设置为预设的颜色
GLES30.glClear(GLES30.GL_COLOR_BUFFER_BIT | GLES30.GL_DEPTH_BUFFER_BIT);
//启用顶点的数组句柄
GLES30.glEnableVertexAttribArray(0);
GLES30.glEnableVertexAttribArray(1);
//绘制模型
mModel.onModelDraw();
//禁止顶点数组句柄
GLES30.glDisableVertexAttribArray(0);
GLES30.glDisableVertexAttribArray(1);
}
}? ? ? ??Model.java
package com.zhyan8.light.model;
import android.content.res.Resources;
import android.opengl.GLES30;
import com.zhyan8.light.R;
import com.zhyan8.light.utils.ArraysUtils;
import com.zhyan8.light.utils.ShaderUtils;
import java.nio.FloatBuffer;
public class Model {
private static final float BALL_RADIUS = 0.5f; // 球半径
private static final int RING_NUM = 400; // 环数（纬度）
private static final int RAW_NUM = 200; // 射线数（经度）
private static final float RING_WIDTH = (float) (Math.PI / RING_NUM); // 环宽度（维度刻度）
private static final float RAW_GAP_ANGLE = (float) (2 * Math.PI / RAW_NUM); // 两条射线间最小夹角（经度刻度）
private static final int VERTEX_DIMENSION = 3; // 顶点坐标维度
private Resources mResources;
private MyTransform mTransform;
private Light mLight;
private float[][] mVertices;
private FloatBuffer[] mVerticesBuffers;
private FloatBuffer[] mNormsBuffers;
private int mProgramId;
private int mPointNumPerRing;
public Model(Resources resources) {
mResources = resources;
mPointNumPerRing = (RAW_NUM + 1) * 2;
mVertices = new float[RING_NUM][mPointNumPerRing * VERTEX_DIMENSION];
mVerticesBuffers = new FloatBuffer[RING_NUM];
mNormsBuffers = new FloatBuffer[RING_NUM];
mTransform = new MyTransform();
mLight = new Light();
}
// 模型创建
public void onModelCreate() {
computeVertexAndNorm();
mProgramId = ShaderUtils.createProgram(mResources, R.raw.vertex_shader, R.raw.fragment_shader);
mLight.onLightCreate(mProgramId);
mTransform.onTransformCreate(mProgramId);
}
// 模型参数变化
public void onModelChange(int width, int height) {
mTransform.onTransformChange(width, height);
}
// 模型绘制
public void onModelDraw() {
GLES30.glUseProgram(mProgramId);
mLight.openLight();
mTransform.onTransformExecute();
for (int i = 0; i < RING_NUM; i++) { // 一环一环绘制纹理
//准备顶点坐标和纹理坐标
GLES30.glVertexAttribPointer(0, VERTEX_DIMENSION, GLES30.GL_FLOAT, false, 0, mVerticesBuffers[i]);
GLES30.glVertexAttribPointer(1, VERTEX_DIMENSION, GLES30.GL_FLOAT, false, 0, mNormsBuffers[i]);
GLES30.glDrawArrays(GLES30.GL_TRIANGLE_STRIP, 0, mPointNumPerRing);
}
}
// 计算顶点坐标与法线坐标
private void computeVertexAndNorm() {
for (int i = 0; i < RING_NUM; i++) {
getRingVertex(i);
mVerticesBuffers[i] = ArraysUtils.getFloatBuffer(mVertices[i]);
mNormsBuffers[i] = ArraysUtils.getFloatBuffer(mVertices[i]);
}
}
// 计算顶点坐标
private void getRingVertex(int ring) {
float phi1 = ring * RING_WIDTH;
float phi2 = phi1 + RING_WIDTH;
float theta = 0f;
int index = 0;
for (int i = 0; i <= RAW_NUM; i++) {
mVertices[ring][index++] = (float) (BALL_RADIUS * Math.sin(phi1) * Math.cos(theta));
mVertices[ring][index++] = (float) (BALL_RADIUS * Math.sin(phi1) * Math.sin(theta));
mVertices[ring][index++] = (float) (BALL_RADIUS * Math.cos(phi1));
mVertices[ring][index++] = (float) (BALL_RADIUS * Math.sin(phi2) * Math.cos(theta));
mVertices[ring][index++] = (float) (BALL_RADIUS * Math.sin(phi2) * Math.sin(theta));
mVertices[ring][index++] = (float) (BALL_RADIUS * Math.cos(phi2));
theta += RAW_GAP_ANGLE;
}
}
}????????Light.java
package com.zhyan8.light.model;
import android.opengl.GLES30;
public class Light {
private int mProgramId;
private int mLightPosHandle;
private int mModelColorHandle;
private int mAmbientLightColorHandle;
private int mLightColorHandle;
private int mMaterialHandle;
private float[] mLightPos = new float[] {0f, 2f, 0f};
private float[] mModelColor = new float[] {0.8f, 0.3f, 0.2f, 1.0f}; // 模型颜色（红色）
private float[] mAmbientLightColor = new float[] {0.7f, 0.7f, 0.7f}; // 环境光颜色（白光）
private float[] mLightColor = new float[] {1f, 1f, 1f, 1.0f}; // 光源颜色（白光）
private float[] mMaterial = new float[] {0.2f, 0.9f, 0.6f}; // 材质对环境光、漫反射光、镜面光的反射系数
public void onLightCreate(int programId) {
mProgramId = programId;
mLightPosHandle = GLES30.glGetUniformLocation(mProgramId, "uLightPos");
mModelColorHandle = GLES30.glGetUniformLocation(mProgramId, "uModelColor");
mAmbientLightColorHandle = GLES30.glGetUniformLocation(mProgramId, "uAmbientLightColor");
mLightColorHandle = GLES30.glGetUniformLocation(mProgramId, "uLightColor");
mMaterialHandle = GLES30.glGetUniformLocation(mProgramId, "uMaterial");
}
public void openLight() {
// 光源位置
GLES30.glUniform3f(mLightPosHandle, mLightPos[0], mLightPos[1], mLightPos[2]);
// 模型颜色
GLES30.glUniform4f(mModelColorHandle, mModelColor[0], mModelColor[1], mModelColor[2], mModelColor[3]);
// 环境光颜色
GLES30.glUniform3f(mAmbientLightColorHandle, mAmbientLightColor[0], mAmbientLightColor[1], mAmbientLightColor[2]);
// 光源颜色
GLES30.glUniform3f(mLightColorHandle, mLightColor[0], mLightColor[1], mLightColor[2]);
// 设置材质系数（材质对环境光、漫反射光、镜面光的反射系数）
GLES30.glUniform3f(mMaterialHandle, mMaterial[0], mMaterial[1], mMaterial[2]);
}
}? ? ? ??MyTransform.java
package com.zhyan8.light.model;
import android.opengl.GLES30;
import android.opengl.Matrix;
public class MyTransform {
private int mProgramId;
private float mViewportRatio;
private int mViewPosHandle;
private int mModelMatrixHandle;
private int mMvpMatrixHandle;
private float[] mViewPos = new float[] {0.0f, 0.0f, 6.0f}; // 相机位置
private float[] mModelMatrix;
private float[] mViewMatrix;
private float[] mProjectionMatrix;
private float[] mMvpMatrix;
private float mTheta = 0;
private float mThetaGap = 0.03f;
private float mRadius = 1f;
private float[] mTranslate = new float[] {0f, 0f, 0f};
// 变换创建
public void onTransformCreate(int programId) {
mProgramId = programId;
mViewPosHandle = GLES30.glGetUniformLocation(mProgramId, "uViewPos");
mModelMatrixHandle = GLES30.glGetUniformLocation(mProgramId, "modelMatrix");
mMvpMatrixHandle = GLES30.glGetUniformLocation(mProgramId, "mvpMatrix");
mViewMatrix = getIdentityMatrix(16, 0);
mMvpMatrix = getIdentityMatrix(16, 0);
Matrix.setLookAtM(mViewMatrix, 0, mViewPos[0], mViewPos[1], mViewPos[2], 0, 0, 0, 0, 1, 0);
}
// 变换参数变换
public void onTransformChange(int width, int height) {
mViewportRatio = 1.0f * width / height;
mProjectionMatrix = getIdentityMatrix(16, 0);
Matrix.frustumM(mProjectionMatrix, 0, -mViewportRatio, mViewportRatio, -1, 1, 3, 10);
}
// 变换执行
public void onTransformExecute() {
mModelMatrix = getIdentityMatrix(16, 0);
mTheta = mTheta > 360 ? mTheta - 360 + mThetaGap : mTheta + mThetaGap;
mTranslate[0] = (float) (mRadius * Math.cos(mTheta));
mTranslate[2] = (float) (mRadius * Math.sin(mTheta));
Matrix.translateM(mModelMatrix, 0, mTranslate[0], mTranslate[1], mTranslate[2]);
// 计算MVP变换矩阵: mvpMatrix = projectionMatrix * viewMatrix * modelMatrix
float[] tempMatrix = new float[16];
Matrix.multiplyMM(tempMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMvpMatrix, 0, mProjectionMatrix, 0, tempMatrix, 0);
GLES30.glUniformMatrix4fv(mModelMatrixHandle, 1, false, mModelMatrix, 0);
GLES30.glUniformMatrix4fv(mMvpMatrixHandle, 1, false, mMvpMatrix, 0);
GLES30.glUniform3f(mViewPosHandle, mViewPos[0], mViewPos[1], mViewPos[2]);
}
private float[] getIdentityMatrix(int size, int offset) {
float[] matrix = new float[size];
Matrix.setIdentityM(matrix, offset);
return matrix;
}
}?? ? ? ?ShaderUtils.java
package com.zhyan8.light.utils;
import android.content.res.Resources;
import android.opengl.GLES30;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
public class ShaderUtils {
//创建程序id
public static int createProgram(Resources resources, int vertexShaderResId, int fragmentShaderResId) {
final int vertexShaderId = compileShader(resources, GLES30.GL_VERTEX_SHADER, vertexShaderResId);
final int fragmentShaderId = compileShader(resources, GLES30.GL_FRAGMENT_SHADER, fragmentShaderResId);
return linkProgram(vertexShaderId, fragmentShaderId);
}
//通过外部资源编译着色器
private static int compileShader(Resources resources, int type, int shaderId){
String shaderCode = readShaderFromResource(resources, shaderId);
return compileShader(type, shaderCode);
}
//通过代码片段编译着色器
private static int compileShader(int type, String shaderCode){
int shader = GLES30.glCreateShader(type);
GLES30.glShaderSource(shader, shaderCode);
GLES30.glCompileShader(shader);
return shader;
}
//链接到着色器
private static int linkProgram(int vertexShaderId, int fragmentShaderId) {
final int programId = GLES30.glCreateProgram();
//将顶点着色器加入到程序
GLES30.glAttachShader(programId, vertexShaderId);
//将片元着色器加入到程序
GLES30.glAttachShader(programId, fragmentShaderId);
//链接着色器程序
GLES30.glLinkProgram(programId);
return programId;
}
//从shader文件读出字符串
private static String readShaderFromResource(Resources resources, int shaderId) {
InputStream is = resources.openRawResource(shaderId);
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line;
StringBuilder sb = new StringBuilder();
try {
while ((line = br.readLine()) != null) {
sb.append(line);
sb.append("\n");
}
br.close();
} catch (Exception e) {
e.printStackTrace();
}
return sb.toString();
}
}? ? ? ??ArraysUtils.java
package com.zhyan8.light.utils;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
public class ArraysUtils {
public static FloatBuffer getFloatBuffer(float[] floatArr) {
FloatBuffer fb = ByteBuffer.allocateDirect(floatArr.length * Float.BYTES)
.order(ByteOrder.nativeOrder())
.asFloatBuffer();
fb.put(floatArr);
fb.position(0);
return fb;
}
}????????vertex_shader.glsl
attribute vec4 aPosition; // 顶点坐标
attribute vec3 aNormal; // 法线向量
uniform vec3 uViewPos; // 相机坐标
uniform vec3 uLightPos; // 光源坐标
uniform vec4 uModelColor; // 模型颜色
uniform vec3 uAmbientLightColor; // 环境光颜色
uniform vec3 uLightColor; // 光源颜色（漫反射、镜面反射）
uniform vec3 uMaterial; // 材质对环境光、漫反射光、镜面光的反射系数
uniform mat4 modelMatrix; // 模型变换
uniform mat4 mvpMatrix; // mvp矩阵变换
varying vec4 vColor; // 合成颜色
// 在片元着色器中计算光照会获得更好更真实的光照效果，但是会比较耗性能
// 环境光的计算
vec4 ambientColor() {
vec3 ambient = uMaterial.x * uAmbientLightColor;
return vec4(ambient, 1.0);
}
// 漫反射的计算
vec4 diffuseColor() {
// 模型变换后的位置
vec3 fragPos = (modelMatrix * aPosition).xyz;
// 光照方向
vec3 lightDirection = normalize(uLightPos - fragPos);
// 模型变换后的法线向量
vec3 normal = normalize(mat3(modelMatrix) * aNormal);
// max(cos(入射角)，0)
float diff = max(dot(normal, lightDirection), 0.0);
// 材质的漫反射系数*max(cos(入射角)，0)*光照颜色
vec3 diffuse = uMaterial.y * diff * uLightColor;
return vec4(diffuse, 1.0);
}
// 镜面光计算，镜面光计算有两种方式，一种是冯氏模型，一种是Blinn改进的冯氏模型
// 冯氏模型: 材质的镜面反射系数*max(0,cos(反射向量与观察向量夹角)^粗糙度*光照颜色
// Blinn改进的冯氏模型: 材质的镜面反射系数*max(0,cos(半向量与法向量的夹角)^粗糙度*光照颜色
// 这里使用的是改进的冯氏模型，基于Half-Vector的计算方式
vec4 specularColor() {
// 模型变换后的位置
vec3 fragPos = (modelMatrix * aPosition).xyz;
// 光照方向
vec3 lightDirection = normalize(uLightPos - fragPos);
// 模型变换后的法线向量
vec3 normal = normalize(mat3(modelMatrix) * aNormal);
// 观察方向
vec3 viewDirection = normalize(uViewPos - fragPos);
// 半向量（观察向量与光照向量的半向量）
vec3 hafVector = normalize(lightDirection + viewDirection);
// max(0,cos(半向量与法向量的夹角)^粗糙度
float diff = pow(max(dot(normal, hafVector), 0.0), 4.0);
vec3 specular = uMaterial.z * diff * uLightColor;
return vec4(specular, 1.0);
}
void main() {
gl_Position = mvpMatrix * aPosition;
vColor = (ambientColor() + diffuseColor() + specularColor()) * uModelColor;
}? ? ? ??fragment_shader.glsl
precision mediump float;
varying vec4 vColor;
void main() {
gl_FragColor = vColor;
}3 运行效果
