FBO 和纹理

Question

我已将两个纹理附加到 FBO。第一个纹理将用于显示深度图。第二个纹理将以正常方式显示对象。

如果我这样做，它会很好地显示深度图。

GLuint atach0 = GL_DEPTH_ATTACHMENT;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
  glDrawBuffers(1,&atach0);
  glClear(GL_DEPTH_BUFFER_BIT);
  glViewport(0.0,0.0,640,480);
  LProjection = glm::ortho(-10.0f,10.0f,-10.0f,10.0f,-500.0f,500.0f);
  LView = glm::lookAt(glm::vec3(0.0f,15.0f,0.000001f),glm::vec3(0.0f,0.0f,0.0f),glm::vec3(0.0f,1.0f,0.0f));
  LViewProjection = LProjection * LView;
  glEnable(GL_DEPTH_TEST);

  ...CUBE3D

glBindFramebuffer(GL_FRAMEBUFFER,0);

glUniform1i(uniforTEX,0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,GL_DEPTH_MAP);

  ...DRAW-DEPTH-MAP!

glBindTexture(GL_TEXTURE_2D,0);

但是如果我这样做，它只会显示一个白屏并且深度图不再可见。

GLuint atach0 = GL_DEPTH_ATTACHMENT;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
  glDrawBuffers(1,&atach0);
  glClear(GL_DEPTH_BUFFER_BIT);
  glViewport(auxrecX,auxrecY,auxrcAn,auxrcAl);
  LProjection = glm::ortho(-10.0f,10.0f,-10.0f,10.0f,-500.0f,500.0f);
  LView = glm::lookAt(glm::vec3(0.0f,15.0f,0.000001f),glm::vec3(0.0f,0.0f,0.0f),glm::vec3(0.0f,1.0f,0.0f));
  LViewProjection = LProjection * LView;
  glEnable(GL_DEPTH_TEST);

  ...CUBE3D

glBindFramebuffer(GL_FRAMEBUFFER,0);

GLuint atach1 = GL_COLOR_ATTACHMENT0;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
  glDrawBuffers(1,&atach1);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glViewport(0,0,640,480);
  Projection = glm::perspective(45.0f,1.333333f,0.01f,1000.0f);
  View = glm::lookAt(glm::vec3(0.0f,0.0f,3.0),glm::vec3(0.0f,0.0f,-15.0f),glm::vec3(0.0f,1.0f,0.0f));
  ViewProjection = Projection * View;
  glEnable(GL_DEPTH_TEST);

  ...CUBE3D

glBindFramebuffer(GL_FRAMEBUFFER,0);   

glUniform1i(uniforTEX,0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,GL_DEPTH_MAP);

  ...DO NOT DRAW NOTHING

glBindTexture(GL_TEXTURE_2D,0);

我需要按照这个顺序来做。因为第一个 "pass" 是为了在阴影贴图中使用深度贴图。我做错了什么？

Answer 1

GL_DEPTH_ATTACHMENT 对 glDrawBuffers 无效。 glDrawBuffers 个缓冲区，片段着色器数据的输出将写入其中。

当你这样做时

GLuint atach0 = GL_DEPTH_ATTACHMENT;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);

然后你会得到一个 GL_INVALID_ENUM 错误。

如果不想写入深度图，请禁用深度测试glDepthMask。深度缓冲区附件无法打开和关闭，也无法像颜色缓冲区一样使用。

进一步

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

无论如何都会清除深度缓冲区。

我认为对于如何设置阴影贴图的帧缓冲区存在基本的误解。您只需要一个用于阴影贴图的帧缓冲区。此帧缓冲区必须仅具有深度缓冲区。

你必须这样做：

GLuint fboShadow;      // framebuffer with depth buffer only (shadow map)
GLuint toShadowDepth;  // texture which is the depth buffer of `fboShadow`

glBindFramebuffer(GL_FRAMEBUFFER, fboShadow);
GLuint atach0 = GL_NONE;
glDrawBuffers(1, &atach0);
glClear(GL_DEPTH_BUFFER_BIT);

glEnable(GL_DEPTH_TEST);
glViewport(auxrecX, auxrecY, auxrcAn, auxrcAl);

// draw the shadow map to the depth buffer only

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

glEnable(GL_DEPTH_TEST);
glViewport(0, 0, 640, 480);

glUniform1i(uniforTEX, 0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, toShadowDepth);

// draw the geometry to the default framebuffer by using the depth map

FBO 和纹理

FBO and Textures

opengl

fbo

glsl