纹理单元重叠？渲染了错误的纹理

Question

我想在片段着色器中使用 4 个纹理。一个是立方体贴图，一个是帧缓冲区上的渲染纹理，最后两个是从图像创建的。

当我尝试在我的片段着色器中调用它们时，无论我调用哪一个，我都会得到一个与我调用的不同或相同的一个（取决于我在尝试修复它时所做的不同迭代）。

这就是我得到它的方式

GLuint FramebufferName = 0;
glGenFramebuffers(1, &FramebufferName);
glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);

GLuint renderedTexture;
glGenTextures(1, &renderedTexture);
glBindTexture(GL_TEXTURE_2D, renderedTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 1024, 1024, 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);
GLenum DrawBuffers[1]={GL_COLOR_ATTACHMENT0};
glDrawBuffers(1, DrawBuffers);

if ( glCheckFramebufferStatus ( GL_FRAMEBUFFER ) == GL_FRAMEBUFFER_COMPLETE )
{
  glViewport(0, 0, 1024, 1024);
  glClearColor( 0.4f, 0.4f, 0.4f, 1.0f );
  glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

  ngl::ShaderLib* shader = ngl::ShaderLib::instance();
  (*shader)["Normal"]->use();
  m_transform.setPosition(0.0f, 0.0f, 0.0f);
  loadMatricesToShader();
  //drawing the quad
  prim->draw("tex");
}

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glViewport(0,0,1024,768);

// grab an instance of the shader manager
ngl::ShaderLib* shader = ngl::ShaderLib::instance();
( *shader )[ "PBR" ]->use();

glUniform1i(renderedTexture, 1);

//initialize environment map
initEnvironment();

initTexture(2, m_glossMapTex, "images/gloss.png");
glUniform1i(m_glossMapTex, 2);
initTexture(3, m_textMap, "images/alege.png");
glUniform1i(m_textMap, 3);

还有 initTexture 和 initEnvironment

void NGLScene::initTexture(const GLuint& texUnit, GLuint &texId, const char *filename) {

glActiveTexture(GL_TEXTURE0 + texUnit);

// Load up the image using NGL routine
ngl::Image img(filename);

glGenTextures(1, &texId);

glBindTexture(GL_TEXTURE_2D, texId);

glTexImage2D (
            GL_TEXTURE_2D,    
            0,                
            img.format(),   
            img.width(),      
            img.height(),     
            0,                
            GL_RGB,          
            GL_UNSIGNED_BYTE, 
            img.getPixels()); 

// Set up parameters for our texture
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
}

void NGLScene::initEnvironment() {

glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);
glActiveTexture (GL_TEXTURE0);
glGenTextures (1, &m_envTex);
glBindTexture(GL_TEXTURE_CUBE_MAP, m_envTex);

initEnvironmentSide(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, "images/sky_zneg.png");
initEnvironmentSide(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, "images/sky_zpos.png");
initEnvironmentSide(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, "images/sky_ypos.png");
initEnvironmentSide(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, "images/sky_yneg.png");
initEnvironmentSide(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, "images/sky_xneg.png");
initEnvironmentSide(GL_TEXTURE_CUBE_MAP_POSITIVE_X, "images/sky_xpos.png");

glGenerateMipmap(GL_TEXTURE_CUBE_MAP);

glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_AUTO_GENERATE_MIPMAP, GL_TRUE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
GLfloat anisotropy;
glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &anisotropy);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAX_ANISOTROPY_EXT, anisotropy);

// Set our cube map texture to on the shader so we can use it
ngl::ShaderLib *shader=ngl::ShaderLib::instance();
shader->use("PBR");
shader->setUniform("envMap", 0);
}

void NGLScene::initEnvironmentSide(GLenum target, const char *filename) {
// Load up the image using NGL routine
ngl::Image img(filename);

glTexImage2D (
  target,          
  0,                
  img.format(),     
  img.width(),     
  img.height(),    
  0,               
  GL_RGBA,         
  GL_UNSIGNED_BYTE, 
  img.getPixels()   
);
}

我觉得我在纹理单元和设置制服方面的知识存在差距，或者我的片段着色器中的制服有问题。

Answer 1

在您的代码中存在一个误解，即必须如何使用 glUniform1i。如果将值分配给制服，则必须通过制服位置索引来识别制服。见Uniform (GLSL)

glUniform1i 的第一个参数必须是制服的位置，而不是命名的纹理对象。

制服的位置可以通过Layout Qualifier在着色器中显式设置

例如

GLSL

layout(location = 7) uniform sampler2D u_gloss;

C++

initTexture(2, m_glossMapTex, "images/gloss.png");
glUniform1i(7, 2); // uniform location 7

如果统一的位置不是由布局限定符设置的，那么统一的位置会在程序链接时自动设置。你可以通过glGetUniformLocation询问这个位置：

例如

GLSL

uniform sampler2D u_gloss;

C++

GLuint program_obj = ... ; // ( *shader )[ "PBR" ]->???
GLint gloss_location = glGetUniformLocation(program_obj , "u_gloss");

initTexture(2, m_glossMapTex, "images/gloss.png");
glUniform1i(gloss_location, 2);