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我目前有一个自定义着色器在天穹上绘制渐变，并希望在天穹前面有一个太阳/月亮（从用户的角度来看）。最简单的方法是为太阳和月亮制作精灵，但出现的问题是精灵卡在天穹内（精灵一半在天穹前面，一半在天穹后面）。我试图用多边形偏移来解决这个问题，但这似乎不适用于精灵对象。

所以我的问题是，如何在天穹顶部设置太阳/月亮，而无需修改我的自定义天穹着色器以添加带有渐变的太阳/月亮纹理（这最终可能非常困难）？

下面是我的天穹天空着色器的代码。

new THREE.ShaderMaterial({
    uniforms: {
        glow: {
            type: "t",
            value: THREE.ImageUtils.loadTexture(DEFAULT_PATH+"glow2.png")
        },
        color: {
            type: "t",
            value: THREE.ImageUtils.loadTexture(DEFAULT_PATH+"sky2.png")
        },
        lightDir: {
            type: "v3",
            value: self.lightPos
        }
    },
    vertexShader: [
        "varying vec3 vWorldPosition;",
        "varying vec3 vPosition;",
        "void main() {",
            "vec4 worldPosition = modelMatrix * vec4(position, 1.0);",
            "vWorldPosition = worldPosition.xyz;",
            "vPosition = position;",
            "gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);",
        "}"
    ].join("\n"),
    fragmentShader: [
        "uniform sampler2D glow;",
        "uniform sampler2D color;",
        "uniform vec3 lightDir;",
        "varying vec3 vWorldPosition;",
        "varying vec3 vPosition;",
        "void main() {",
            "vec3 V = normalize(vWorldPosition.xzy);",
            "vec3 L = normalize(lightDir.xzy);",
            "float vl = dot(V, L);",
            "vec4 Kc = texture2D(color, vec2((L.y + 1.0) / 2.0, V.y));",
            "vec4 Kg = texture2D(glow,  vec2((L.y + 1.0) / 2.0, vl));",
            "gl_FragColor = vec4(Kc.rgb + Kg.rgb * Kg.a / 2.0, Kc.a);",
        "}",
    ].join("\n")
});
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1 回答 1

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Make sure your skydome is drawn before any other object and disable the depthWrite / depthTest flags on the material (depthWrite being the important thing here):

yourmaterial = new THREE.ShaderMaterial({...});
yourmaterial.depthWrite = false;
yourmaterial.depthTest = false;
skydome.renderDepth = 1e20;

where skydome is the mesh on which you have applied yourmaterial.

于 2013-04-27T09:49:39.117 回答