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java - 如何在OpenGL中显示立方体的背景颜色以及两个纹理的颜色

问题描述

我正在尝试将两个纹理添加到 3d 立方体。我实现了我的目标，但在途中我失去了背景颜色。

我想显示图像的原始颜色以及背景颜色。我使用混合，但它显示背景完全黑暗。

这是我的 fragmentShaderCode 的样子：

private final String fragmentShaderCode =
        "precision mediump float;" +
                "uniform sampler2D u_Texture0;" +
                "uniform sampler2D u_Texture1;" +
                "uniform vec4 aColor;" +
                "varying vec2 v_TexCoordinate0;" +
                "varying vec2 v_TexCoordinate1;" +
                "void main() {" +
                "   vec4 base = texture2D(u_Texture0, v_TexCoordinate0);" +
                "   vec4 overlay = texture2D(u_Texture1, v_TexCoordinate1);" +
                "   mediump float ra = (overlay.a) * overlay.r + (1.0 - overlay.a) * base.r;" +
                "   mediump float ga = (overlay.a) * overlay.g + (1.0 - overlay.a) * base.g;" +
                "   mediump float ba = (overlay.a) * overlay.b + (1.0 - overlay.a) * base.b;" +
                "   gl_FragColor = vec4(mix(aColor.rgb, vec4(ra, ga, ba, 1.0).rgb , vec4(ra, ga, ba, 1.0).a), 1.0);" +
                "}";

标签： javaandroidopengl-es

解决方案

The alpha channel of vec4(ra, ga, ba, 1.0) is 1.0. Therefore the result of vec4(ra, ga, ba, 1.0).a is always 1.0.

You need to use the texture's alpha channels. e.g.: max(base.a, overlay.a):

vec3 textureColor = vec3(ra, ga, ba);
float textureAlpha = max(base.a, overlay.a);
gl_FragColor = vec4(mix(aColor.rgb, textureColor, textureAlpha), 1.0);

Simplify the code by mixing the texture colors with the mix function:

void main() {
    vec4 base = texture2D(u_Texture0, v_TexCoordinate0);
    vec4 overlay = texture2D(u_Texture1, v_TexCoordinate1);
    vec3 textureColor = mix(base.rgb, overlay.rgb, overlay.a);
    float textureAlpha = max(base.a, overlay.a);
    gl_FragColor = vec4(mix(aColor.rgb, textureColor, textureAlpha), 1.0); 
}

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