opengl - 将深度作为纹理从帧缓冲区渲染到显示窗口
问题描述
我是 OpenGL 的新手。我想使用帧缓冲区读取并保存渲染场景中的所有深度值。我设法将其设置为附加到深度组件的帧缓冲区。但是当我将深度纹理渲染到默认帧缓冲区(显示窗口)时,它只显示白色,即使我对深度值进行了线性化(教程来自https://learnopengl.com/)。当我在默认帧缓冲区片段着色器中从gl_FragCoord.z访问深度值并且绘图也可以时,我得到了一个深度图,但是当将深度作为纹理从单独的帧缓冲区发送到默认值时,深度图像是强白色。
我为此编写的代码如下:
自定义帧缓冲顶点和片段着色器
const char* vertexShaderFBO =
"#version 330\n"
"layout (location = 0) in vec3 vp;"
"uniform mat4 camera;"
"uniform mat4 projection;"
"void main() {"
" gl_Position = camera * projection * vec4(vp.x, vp.y, vp.z, 1.0);"
"}";
const char* fragmentShaderFBO =
"#version 330\n"
"layout (location = 0) out float frag_depth;"
"float near = 0.1;"
"float far = 100;"
"float LinearizeDepth(float depth)"
"{"
" float z = depth * 2.0 - 1.0;"
" return (2.0 * near * far) / (far + near - z * (far - near));"
"}"
"void main() {"
" float linearDepth = LinearizeDepth(gl_FragCoord.z) / far;" // divided by far is just to visualize depth
" frag_depth = linearDepth ;"
"}";
默认帧缓冲区顶点和片段着色器
const char* vertexShader =
"#version 330\n"
"layout (location = 0) in vec3 vp;"
"uniform mat4 camera;"
"uniform mat4 projection;"
"void main() {"
" gl_Position = camera * projection * vec4(vp.x, vp.y, vp.z, 1.0);"
"}";
const char* fragmentShader =
"#version 330\n"
"out vec4 frag_colour;"
"uniform sampler2D depthSampler;"
"in vec2 texCoords;"
"void main() {"
" float depthVal = texture(depthSampler, texCoords).r;"
" frag_colour = vec4(vec3(depthVal), 1);"
"}";
深度纹理
GLuint setDepthTexture()
{
GLuint texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, SCREEN_SIZE.x, SCREEN_SIZE.y, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_NONE);
return texture;
}
渲染关闭文件
int renderOFF(Vertices* vertices, Faces* faces, Views* views)
{
// initializaion
...
...
glEnable(GL_DEPTH_TEST); // enable depth buffer
glDepthFunc(GL_LESS); // If pixel closer to camera then overwrite the existing pixel
...
...
// create framebuffer shader
GLuint shaderProgramFBO = createShader(vertexShaderFBO, fragmentShaderFBO);
// create renderer shader
GLuint shaderProgram = createShader(vertexShader, fragmentShader);
//set texture
GLuint depthTexture = setDepthTexture();
// set framebuffer
unsigned int fbo;
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
// attach texture to framebuffer
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthTexture, 0);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{
std::cout << "Failed to bind framebuffer" << std::endl;
return -1;
}
// Use no color attachment
glDrawBuffer(GL_NONE);
glReadBuffer(GL_NONE);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glUseProgram(shaderProgram);
glUniform1i(glGetUniformLocation(shaderProgram, "depthSampler"), 0);
// set camera
...
...
while(!glfwWindowShouldClose(glfWwindow))
{
// check OpenGL error
GLenum err;
while ((err = glGetError()) != GL_NO_ERROR) {
std::cout << "OpenGL error: " << err << std::endl;
}
// bind to custom framebuffer
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glClearColor(0, 0, 0, 1); // clear screen to black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(shaderProgramFBO);
...
glEnable(GL_DEPTH_TEST);
glBindVertexArray(vao);
glDrawElements(GL_TRIANGLES, faces->size, GL_UNSIGNED_INT, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
// default framebuffer
glClearColor(0, 0, 0, 1); // clear screen to black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
processKeyBoardInput(glfWwindow);
...
//glDisable(GL_DEPTH_TEST);
glBindVertexArray(vao);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, depthTexture);
glDrawElements(GL_TRIANGLES, faces->size, GL_UNSIGNED_INT, 0);
glfwSwapBuffers(glfWwindow);
glfwPollEvents();
sleep(1);
}
glDeleteFramebuffers(1, &fbo);
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &vbo);
glfwTerminate();
return 0;
}
解决方案
片段着色器将 [ near , far ] 范围内的深度值分配给 [0.0, 1.0] 范围内的颜色值。如果所有几何体都在接近 0.0 的区域内,则渲染将显示为几乎黑色,因为 0.1 被渲染为黑色,100 被渲染为白色。将查看体积(查看平截头体)的近平面和远平面尽可能靠近几何体,以利用 0.0 到 1.0 之间的整个范围。
当近平面接近 0 时,您的片段着色器将正常工作。随着近平面变大,您应该使用:
float linearDepth = LinearizeDepth(gl_FragCoord.z) / far;
float linearDepth = (LinearizeDepth(gl_FragCoord.z) - near) / (far - near);
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