使用Mesh绘制三角形 中介绍了绘制三角形的方法,本文将介绍绘制正方形的方法。
libGDX 以点、线段、三角形为图元,没有提供绘制矩形内部的接口。要绘制矩形内部,必须通过三角形拼接而成,如下图,是通过GL_TRIANGLE_FAN 模式绘制矩形。
绘制的坐标点如下,屏幕中心为坐标原点,向右和向上分别为 x 轴和 y 轴正方向。
float[] vertices = {
-0.5f, -0.5f, 0.0f, // 左下
0.5f, -0.5f, 0.0f, // 右下
0.5f, 0.5f, 0.0f, // 右上
-0.5f, 0.5f, 0.0f // 左上
};
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("Square");
new Lwjgl3Application(new Square(), config);
}
}
Square.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.VertexAttribute;
import com.badlogic.gdx.graphics.VertexAttributes.Usage;
import com.badlogic.gdx.graphics.glutils.ShaderProgram;
public class Square extends ApplicationAdapter {
private ShaderProgram mShaderProgram;
private Mesh mMesh;
@Override
public void create() {
initShader();
initMesh();
}
@Override
public void render() {
Gdx.gl.glClearColor(0.455f, 0.725f, 1.0f, 1.0f);
Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT);
mShaderProgram.bind();
mMesh.render(mShaderProgram, GL30.GL_TRIANGLE_FAN);
}
@Override
public void dispose() {
mShaderProgram.dispose();
mMesh.dispose();
}
private void initShader() { // 初始化着色器程序
String vertex = Gdx.files.internal("shaders/square_vertex.glsl").readString();
String fragment = Gdx.files.internal("shaders/square_fragment.glsl").readString();
mShaderProgram = new ShaderProgram(vertex, fragment);
}
private void initMesh() { // 初始化网格
float[] vertices = {
-0.5f, -0.5f, 0.0f, // 左下
0.5f, -0.5f, 0.0f, // 右下
0.5f, 0.5f, 0.0f, // 右上
-0.5f, 0.5f, 0.0f // 左上
};
short[] indices = {0, 1, 2, 3};
VertexAttribute vertexPosition = new VertexAttribute(Usage.Position, 3, "a_position");
mMesh = new Mesh(true, vertices.length / 3, indices.length, vertexPosition);
mMesh.setVertices(vertices);
mMesh.setIndices(indices);
}
}
square_vertex.glsl
#version 300 es
precision mediump float; // 声明float型变量的精度为mediump
out vec4 fragColor;
void main() {
fragColor = vec4(1, 0, 0, 0);
}
square_fragment.glsl
#version 300 es
in vec3 a_position;
void main() {
gl_Position = vec4(a_position, 1.0);
}
运行效果如下。
Square.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.VertexAttribute;
import com.badlogic.gdx.graphics.VertexAttributes.Usage;
import com.badlogic.gdx.graphics.glutils.ShaderProgram;
public class Square extends ApplicationAdapter {
private ShaderProgram mShaderProgram;
private Mesh mMesh;
private float mRatio;
@Override
public void create() {
initShader();
initMesh();
}
@Override
public void render() {
Gdx.gl.glClearColor(0.455f, 0.725f, 1.0f, 1.0f);
Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT);
mShaderProgram.bind();
mShaderProgram.setUniformf("u_wh_ratio", mRatio);
mMesh.render(mShaderProgram, GL30.GL_TRIANGLE_FAN);
}
@Override
public void dispose() {
mShaderProgram.dispose();
mMesh.dispose();
}
private void initShader() { // 初始化着色器程序
String vertex = Gdx.files.internal("shaders/square_vertex.glsl").readString();
String fragment = Gdx.files.internal("shaders/square_fragment.glsl").readString();
mShaderProgram = new ShaderProgram(vertex, fragment);
mRatio = 1.0f * Gdx.graphics.getWidth() / Gdx.graphics.getHeight();
}
private void initMesh() { // 初始化网格
float[] vertices = {
-0.5f, -0.5f, 0.0f, // 左下
0.5f, -0.5f, 0.0f, // 右下
0.5f, 0.5f, 0.0f, // 右上
-0.5f, 0.5f, 0.0f // 左上
};
short[] indices = {0, 1, 2, 3};
VertexAttribute vertexPosition = new VertexAttribute(Usage.Position, 3, "a_position");
mMesh = new Mesh(true, vertices.length / 3, indices.length, vertexPosition);
mMesh.setVertices(vertices);
mMesh.setIndices(indices);
}
}
square_vertex.glsl
#version 300 es
in vec3 a_position;
uniform float u_wh_ratio; // 屏幕宽高比
void main() {
gl_Position = vec4(a_position, 1.0);
if (u_wh_ratio > 1.0) {
gl_Position.x /= u_wh_ratio;
} else {
gl_Position.y *= u_wh_ratio;
}
}
square_fragment.glsl
#version 300 es
precision mediump float; // 声明float型变量的精度为mediump
out vec4 fragColor;
void main() {
fragColor = vec4(0, 1, 0, 0);
}