【libGDX】Mesh立方体贴图（6张图）-编程知识

1 前言

本文通过一个立方体贴图的例子，讲解三维纹理贴图的应用，案例中使用 6 张不同的图片给立方体贴图，图片如下。

读者如果对 libGDX 不太熟悉，请回顾以下内容。

使用Mesh绘制三角形
使用Mesh绘制矩形
使用Mesh绘制圆形
使用Mesh绘制立方体
Mesh纹理贴图

2 立方体贴图

本节将使用 Mesh、ShaderProgram、Shader 实现立方体贴图，OpenGL ES 的实现见博客 → 立方体贴图（6张图），本节完整代码资源见 → libGDX Mesh立方体贴图（6张图）。

DesktopLauncher.java

package com.zhyan8.game;import com.badlogic.gdx.backends.lwjgl3.Lwjgl3Application;
import com.badlogic.gdx.backends.lwjgl3.Lwjgl3ApplicationConfiguration;public class DesktopLauncher {public static void main (String[] arg) {Lwjgl3ApplicationConfiguration config = new Lwjgl3ApplicationConfiguration();config.setForegroundFPS(60);config.setTitle("CubeChartlet");new Lwjgl3Application(new CubeChartlet(), config);}
}

CubeChartlet.java

package com.zhyan8.game;import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL30;
import com.badlogic.gdx.graphics.Mesh;
import com.badlogic.gdx.graphics.PerspectiveCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.VertexAttribute;
import com.badlogic.gdx.graphics.VertexAttributes.Usage;
import com.badlogic.gdx.graphics.glutils.ShaderProgram;
import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Vector3;public class CubeChartlet extends ApplicationAdapter {private PerspectiveCamera mCamera;private ShaderProgram mShaderProgram;private Mesh mMesh;private Texture[] mTextures;private Vector3 mRotateAxis; // 旋转轴private int mRotateAgree = 0; // 旋转角度Matrix4 mModelMatrix; // 模型变换矩阵@Overridepublic void create() {initCamera();initShader();initMesh();initTextures();mRotateAxis = new Vector3(0.5f, 1f, 1f);mModelMatrix = new Matrix4();}@Overridepublic void render() {Gdx.gl.glClearColor(0.455f, 0.725f, 1.0f, 1.0f);Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT | GL30.GL_DEPTH_BUFFER_BIT);Gdx.gl.glEnable(GL30.GL_DEPTH_TEST);mShaderProgram.bind();transform();renderCube();}@Overridepublic void dispose() {mShaderProgram.dispose();mMesh.dispose();}private void renderCube() {for (int i = 0; i < mTextures.length; i++) { // 给每个面都贴图// mShaderProgram.setUniformi("u_texture", 0); // 设置纹理单元mTextures[i].bind(0);mMesh.render(mShaderProgram, GL30.GL_TRIANGLE_FAN, i * 4, 4);}}private void initCamera() { // 初始化相机mCamera = new PerspectiveCamera(67, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());mCamera.near = 0.3f;mCamera.far = 1000f;mCamera.position.set(0f, 0f, 4f);mCamera.lookAt(0, 0, 0);mCamera.update();}private void initShader() { // 初始化着色器程序String vertex = Gdx.files.internal("shaders/square_chartlet_vertex.glsl").readString();String fragment = Gdx.files.internal("shaders/square_chartlet_fragment.glsl").readString();mShaderProgram = new ShaderProgram(vertex, fragment);}private void initMesh() { // 初始化网格float[] vertices = Model.vertices;short[] indices = Model.indices;VertexAttribute vertexPosition = new VertexAttribute(Usage.Position, 3, "a_position");VertexAttribute texCoords = new VertexAttribute(Usage.TextureCoordinates, 2, "a_texCoord0");mMesh = new Mesh(true, vertices.length / 5, indices.length, vertexPosition, texCoords);mMesh.setVertices(vertices);mMesh.setIndices(indices);}private void initTextures() {mTextures = new Texture[Model.texturePaths.length];for (int i = 0; i < mTextures.length; i++) {mTextures[i] = new Texture(Gdx.files.internal(Model.texturePaths[i]));}}private void transform() { // MVP矩阵变换mRotateAgree = (mRotateAgree + 2) % 360;mRotateAxis.x = mRotateAgree / 180f - 1;mRotateAxis.y = (float) Math.sin(mRotateAgree / 180f * Math.PI * 0.7f);mRotateAxis.z = (float) Math.cos(mRotateAgree / 180f * Math.PI * 0.5f);mModelMatrix.idt(); // 模型变换矩阵单位化mModelMatrix.rotate(mRotateAxis, mRotateAgree);Matrix4 mvpMatrix = mModelMatrix.mulLeft(mCamera.combined);mShaderProgram.setUniformMatrix("u_mvpTrans", mvpMatrix);}
}

Model.java

package com.zhyan8.game;public class Model {private static float r = 1.0f;public static String[] texturePaths = new String[] {"textures/a1.png", "textures/a2.png", "textures/a3.png","textures/a4.png", "textures/a5.png", "textures/a6.png"};public static float[] vertices = new float[] {// 前面r, r, r, 0f, 0f, // 0-r, r, r, 1f, 0f, // 1-r, -r, r, 1f, 1f, // 2r, -r, r, 0f, 1f, // 3// 后面r, r, -r, 0f, 0f, // 4-r, r, -r, 1f, 0f, // 5-r, -r, -r, 1f, 1f, // 6r, -r, -r, 0f, 1f, // 7// 上面r, r, r, 0f, 0f, // 8r, r, -r, 1f, 0f, // 9-r, r, -r, 1f, 1f, // 10-r, r, r, 0f, 1f, // 11// 下面r, -r, r, 0f, 0f, // 12r, -r, -r, 1f, 0f, // 13-r, -r, -r, 1f, 1f, // 14-r, -r, r, 0f, 1f, // 15// 右面r, r, r, 0f, 0f, // 16r, r, -r, 1f, 0f, // 17r, -r, -r, 1f, 1f, // 18r, -r, r, 0f, 1f, // 19// 左面-r, r, r, 0f, 0f, // 20-r, r, -r, 1f, 0f, // 21-r, -r, -r, 1f, 1f, // 22-r, -r, r, 0f, 1f // 23};public static short[] indices = new short[] {0, 1, 2, 3, // 前面4, 5, 6, 7, // 上面8, 9, 10, 11, // 右面12, 13, 14, 15, // 后面16, 17, 18, 19, // 下面20, 21, 22, 23 // 左面};
}

square_chartlet_vertex.glsl

#version 300 esin vec3 a_position;
in vec2 a_texCoord0;uniform mat4 u_mvpTrans; // MVP矩阵变换out vec2 v_texCoord0;void main() {gl_Position = u_mvpTrans * vec4(a_position, 1.0);v_texCoord0 = a_texCoord0;
}

square_chartlet_fragment.glsl

#version 300 es
precision mediump float; // 声明float型变量的精度为mediumpin vec2 v_texCoord0;uniform sampler2D u_texture;out vec4 fragColor;void main() {fragColor = texture(u_texture, v_texCoord0);
}

运行效果如下。