java - libGDX 着色器坐标和相机位置

Question

我正在使用 libGDX、Tiled Map 和 Box2D 开发平台游戏。我想应用一些着色器。

我想要一个贴在英雄身上的晕影效果。对于晕影效果，我使用了 this tutorial .我遇到的问题是:如果相机是固定的，我得到的正是我想要的。小插图坚持英雄。但是，如果摄像机移动(这发生在滚动平台游戏中)，晕影效果就不会粘在英雄身上。

Here is a video that illustrates my problem

看来我必须考虑相机位置来计算晕影效果的坐标，但我不知道如何。这是我用于小插图的片段着色器:

varying vec4 v_color;   
varying vec2 v_texCoord0;

uniform vec2 u_resolution;
uniform float u_PosX, u_PosY;
uniform sampler2D u_sampler2D;  

const float outerRadius = 10, innerRadius = 1, intensity = .5;

void main(){
    vec4 color = texture2D(u_sampler2D, v_texCoord0) * v_color;

    vec2 relativePosition = gl_FragCoord.xy / u_resolution - vec2(u_PosX, u_PosY); //Position of the vignette
    relativePosition.x *= u_resolution.x / u_resolution.y;  //The vignette is a circle
    float len = length(relativePosition);
    float vignette = smoothstep(outerRadius, innerRadius, len);
    color.rgb = mix(color.rgb, color.rgb * vignette, intensity);

    gl_FragColor = color;
}

在游戏画面中，相关代码为:

public TestScreen(final MyGdxGame gam){    

    camera = new MyCamera(); 
    camera.setToOrtho(false, width, height);
    camera.update();

    vertexShader = Gdx.files.internal("Shaders/vVignette.glsl").readString();
    fragmentShader = Gdx.files.internal("Shaders/fVignette.glsl").readString();
    shaderProgram = new ShaderProgram(vertexShader,fragmentShader);

    shaderProgram.begin();
    shaderProgram.setUniformf("u_resolution", camera.viewportWidth, camera.viewportHeight);
    shaderProgram.end();            
}


public void render(float delta) {
    Gdx.gl.glClearColor(0.1f,0.1f,0.1f,1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    camera.update();

    //calculation of the position of the effect depending on the position of the hero
    posX = (Gdx.graphics.getWidth()/camera.viewportWidth) * hero.bodyHero.getPosition().x/camera.viewportWidth;
    posY = (Gdx.graphics.getHeight()/camera.viewportHeight) * hero.bodyHero.getPosition().y/camera.viewportHeight;  

    shaderProgram.begin();
    shaderProgram.setUniformf("u_PosX", posX);
    shaderProgram.setUniformf("u_PosY", posY);
    shaderProgram.end();
}

正如我所说，如果相机不移动，此代码将完美运行。但是由于当相机移动时它不起作用，我认为问题与相机投影有关，我在 render() 中尝试了这段代码，但没有取得更好的成功 :

Vector3 PosHero = new Vector3();
PosHero.set(hero.bodyHero.getPosition().x, hero.bodyHero.getPosition().y, 0);
camera.unproject(PosHero);

posX = (Gdx.graphics.getWidth()/camera.viewportWidth) * PosHero.x/camera.viewportWidth;
posY = (Gdx.graphics.getHeight()/camera.viewportHeight) * PosHero.y/camera.viewportHeight;

shaderProgram.begin();
shaderProgram.setUniformf("u_PosX", posX);
shaderProgram.setUniformf("u_PosY", posY);
shaderProgram.end();

Answer 1

天哪...我为此苦苦挣扎了将近 2 周，我的问题是一个简单的错误:

正如我所想，问题与相机投影有关。在我在消息末尾提供的代码中，我使用了 camera.unproject(PosHero);，但我需要改用 camera.project(PosHero);!

最后是我用来为片段着色器提供正确坐标的代码:

Vector3 PosHero = new Vector3();
PosHero.set(hero.bodyHero.getPosition().x, hero.bodyHero.getPosition().y, 0);
camera.project(PosHero);

posX = PosHero.x/camera.viewportWidth;
posY = PosHero.y/camera.viewportHeight;

shaderProgram.begin();
shaderProgram.setUniformf("u_PosX", posX);
shaderProgram.setUniformf("u_PosY", posY);
shaderProgram.end();