WebGL上的多纹理GL_纹理1问题

我正在学习在WebGL上使用multitexture。我有以下着色器代码片段：

uniform int flag;

uniform sampler2D texture0;
uniform sampler2D texture1;

varying vec2 v_texCoord;

void main()
{
    vec2 texCoord = vec2(v_texCoord.s, 1.0 - v_texCoord.t);

    vec4 texel0 = texture2D(texture0, texCoord);
    vec4 texel1 = texture2D(texture1, texCoord);

    if (1 == flag) 
    {
        gl_FragColor = texel1;

    } else
    {
        gl_FragColor = texel0;
    }
}

gl.uniform1i(gl.getUniformLocation(gl.program, "flag"), 1);
gl.uniform1i(gl.getUniformLocation(gl.program, "texture0"), 0);     // Texture Unit 0
gl.uniform1i(gl.getUniformLocation(gl.program, "texture1"), 1);     // Texture Unit 1
// Activate 2 textures
gl.enable(gl.TEXTURE_2D);

gl.activeTexture(gl.GL_TEXTURE0);    
gl.bindTexture(gl.TEXTURE_2D, photoTexture0);

gl.activeTexture(gl.GL_TEXTURE1);    
gl.bindTexture(gl.TEXTURE_2D, photoTexture1);

另外，我的JavaScript代码片段：

uniform int flag;

uniform sampler2D texture0;
uniform sampler2D texture1;

varying vec2 v_texCoord;

void main()
{
    vec2 texCoord = vec2(v_texCoord.s, 1.0 - v_texCoord.t);

    vec4 texel0 = texture2D(texture0, texCoord);
    vec4 texel1 = texture2D(texture1, texCoord);

    if (1 == flag) 
    {
        gl_FragColor = texel1;

    } else
    {
        gl_FragColor = texel0;
    }
}

gl.uniform1i(gl.getUniformLocation(gl.program, "flag"), 1);
gl.uniform1i(gl.getUniformLocation(gl.program, "texture0"), 0);     // Texture Unit 0
gl.uniform1i(gl.getUniformLocation(gl.program, "texture1"), 1);     // Texture Unit 1
// Activate 2 textures
gl.enable(gl.TEXTURE_2D);

gl.activeTexture(gl.GL_TEXTURE0);    
gl.bindTexture(gl.TEXTURE_2D, photoTexture0);

gl.activeTexture(gl.GL_TEXTURE1);    
gl.bindTexture(gl.TEXTURE_2D, photoTexture1);

photoTexture1（texture1）仅在屏幕上显示黑色。我可以正确显示photoTexture0（texture0）。似乎photoTexture1（texture1）在着色器中不可见

由于上面的代码不起作用，而且我是新手，我想知道我是否做错了什么和/或我误解了multitexture如何工作的概念

感谢您的帮助。提前感谢你的帮助

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注意：我在

上发现并修复了该问题

gl.activeTexture(gl.TEXTURE0);   // remove the "GL_" on GL_TEXTURE0
gl.bindTexture(gl.TEXTURE_2D, photoTexture0);

gl.uniform1i(gl.getUniformLocation(gl.program, "texture1"), 0);
gl.activeTexture(gl.TEXTURE1);     // remove the "GL_" on GL_TEXTURE1

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我从用C语言编写的示例中剪切“n”粘贴GL\u Texture E0。

WebGL在Texture E0、Texture E1等上不使用前缀“GL\uU”。请参阅WebGL规范