无法在GLSL Fragment Shader中使用两个统一变量(仅限第一个工作)

Question

我试图在片段着色器中混合两种纹理的颜色.但不幸的是,我在实际工作之前就被卡住了.

这是着色器设置:

const char* vertex = "void main(){ \n\
                gl_Position = ftransform(); \n\
                        gl_TexCoord[0] = gl_MultiTexCoord0;\n\
                        gl_TexCoord[1] = gl_MultiTexCoord1;\n\
                     }\n";

const char* fragment = "\
                       uniform sampler2D userT;\
                       uniform sampler2D videoTex; \
                       \n\
                       void main(){\n\
                            vec4 texel = texture2D(userT, gl_TexCoord[0].st);\n\
                            gl_FragColor = texel;\n\
                        }\n";

m_vertexShader = glCreateShader(GL_VERTEX_SHADER);
m_fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

glShaderSource( m_vertexShader, 1, &vertex, NULL );
glShaderSource( m_fragmentShader, 1, &fragment, NULL );

glCompileShader( m_vertexShader );
glCompileShader( m_fragmentShader );

m_silhouetteShaderProg = glCreateProgram();
glAttachShader( m_silhouetteShaderProg, m_vertexShader );
glAttachShader( m_silhouetteShaderProg, m_fragmentShader );
glLinkProgram( m_silhouetteShaderProg );

现在片段着色器只显示其中一个txtures,稍后会更改,如果我在这个地方都有两个纹理.

我确实检查了编译和链接错误,一切都很好.

这是我的显示功能:

 .... setup of the textures m_videoTexture and m_userPixelTexture with glTexSubImage2D calls ....

glUseProgram( m_silhouetteShaderProg );

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_videoTexture);
GLint videoTexUnif = glGetUniformLocation( m_silhouetteShaderProg, "videoTex" );
glUniform1i( videoTexUnif, 0 );

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, m_userPixelTexture);
GLint userTexUnif = glGetUniformLocation( m_silhouetteShaderProg, "userT" );
glUniform1i( userTexUnif, 1 );

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

glBegin(GL_QUADS);
    glMultiTexCoord2f(GL_TEXTURE0, 1.0f, 0.0f);
    glMultiTexCoord2f(GL_TEXTURE1, 1.0f, 0.0f);
    glVertex3f(-0.5f, -0.5f, 0.0f);
    glMultiTexCoord2f(GL_TEXTURE0, 1.0f, 1.0f);
    glMultiTexCoord2f(GL_TEXTURE1, 1.0f, 1.0f*stretch);
    glVertex3f(-0.5f, 0.5f, 0.0f);
    glMultiTexCoord2f(GL_TEXTURE0, 0.0f, 1.0f);
    glMultiTexCoord2f(GL_TEXTURE1, 0.0f, 1.0f*stretch);
    glVertex3f(0.5f, 0.5f, 0.0f);
    glMultiTexCoord2f(GL_TEXTURE0, 0.0f, 0.0f);
    glMultiTexCoord2f(GL_TEXTURE1, 0.0f, 0.0f);
    glVertex3f(0.5f, -0.5f, 0.0f);
glEnd();

glUseProgram( 0 );
glActiveTexture(GL_TEXTURE0);

我的问题是我只能使用"glGetUniformLocation"访问我的片段着色器("userT")的第一个制服.调用:"GLint videoTexUnif = glGetUniformLocation(m_silhouetteShaderProg,"videoTex");" 结果为"-1".

如果我改变片段着色器中制服的顺序,我可以访问"videoTex"但不能访问"userT".

我在片段着色器中看到了很多使用两个制服的例子,所以我强烈认为这是可能的.但是我在这里做错了什么？

Answer 1

您的第二个统一采样器由GLSL编译器优化,因为它没有被使用.在链接的GLSL程序中没有这样的统一,因此您的程序逻辑应该考虑到这一点(任何统一都可以根据您的代码进行优化).