OpenGL 渲染到纹理

标签 opengl opengl-es opengl-3 blending

enter image description here如何使用帧缓冲区对象渲染纹理并将该纹理用作着色器的输入。

我需要为可编程混合执行此操作。

我能够单独创建 FBO 和纹理，但无法渲染到该纹理并附加我的帧缓冲区对象。

我需要渲染到纹理，因为我想将此纹理传递给我的着色器，以便我能够编写自己的可编程混合方程。

#include <glad/glad.h>
#include <GLFW\glfw3.h> 
#include <iostream>
#include "shader.h"


#include "std_image.h"

using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        cout << "Failed to create GLFW window" <<endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        cout << "Failed to initialize GLAD" <<endl;
        return -1;
    }
    glViewport(0, 0, 800, 600);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    ///////////////////////////////////////////////////////////////////////////////////

    Shader ourShader("Shader.vs", "Shader.fs");

    Shader ourShader2("Shader.vs", "Shader2.fs");

    unsigned int FBO;
    glGenFramebuffers(1, &FBO);
    glBindFramebuffer(GL_FRAMEBUFFER, FBO);

    unsigned int attachment_index_color_texture = 0;
    glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + attachment_index_color_texture, GL_UNSIGNED_BYTE, 0);

    glBindFramebuffer(GL_FRAMEBUFFER, 0);    //unbind framebuffer







    float vertices[] = {
        // positions          // colors           // texture coords
        0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f,   // top right
        0.5f, -0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        -0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   0.0f, 0.0f,   // bottom left
        -0.5f,  0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   0.0f, 1.0f    // top left 
    };
    unsigned int indices[] = {
        0, 1, 3, // first triangle
        1, 2, 3  // second triangle
    };

    float vertices2[] = {
        // positions          // colors           // texture coords
        0.75f,  0.75f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 1.0f,   // top right
        0.75f, 0.0f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        0.0f, 0.0f, 0.0f,  0.0f,1.0f, 0.0f,   0.0f, 0.0f,   // bottom left
        0.0f,  0.75f, 0.0f,  0.0f, 1.0f, 0.0f,   0.0f, 1.0f    // top left 
    };
    unsigned int indices2[] = {
        0, 1, 2, // first triangle
        0, 2, 3  // second triangle
    };


    unsigned int VBO[2],VAO[2],EBO[2];

    glGenVertexArrays(2, VAO);
    glGenBuffers(2, VBO);
    glGenBuffers(2, EBO);

    glBindVertexArray(VAO[0]);
    glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    glBindVertexArray(0);

    glBindVertexArray(VAO[1]);
    glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices2), indices2, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE);


    while (!glfwWindowShouldClose(window))
    {
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);



        ourShader.use();

        glBindVertexArray(VAO[0]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

        ourShader2.use();

        glBindVertexArray(VAO[1]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    /*glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteBuffers(1, &EBO);*/

    glfwTerminate();
    return 0;
}

编辑1:

我现在将我的纹理附加到 fbo，也在我的 textrue 上渲染，如下所示:
while (!glfwWindowShouldClose(window))
    {
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);



        ourShader.use();
        glBindVertexArray(VAO[0]);
        unsigned int FBO, color, depth;

        glGenFramebuffers(1, &FBO);
        glGenTextures(1, &color);


        glBindFramebuffer(GL_FRAMEBUFFER, FBO);
        glBindTexture(GL_TEXTURE_2D, color);
        glGenRenderbuffers(1, &depth);

        glTexImage2D(GL_TEXTURE_2D,
            0,
            GL_RGBA,
            800, 600,
            0,
            GL_RGBA,
            GL_UNSIGNED_BYTE,
            NULL);

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

        glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, color, 0);

        GLenum DrawBuffers[1] = { GL_COLOR_ATTACHMENT0 };
        glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers

        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
            return false;

        glBindFramebuffer(GL_FRAMEBUFFER, FBO);
        glViewport(0, 0, 800, 600); // Render on the whole framebuffer, complete from the lower left corner to the upper right


        glBindFramebuffer(GL_FRAMEBUFFER, 0);


        ourShader2.use();

        glBindVertexArray(VAO[1]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);



        glfwSwapBuffers(window);
        glfwPollEvents();
    }

剩下的一个问题是如何在着色器中传递纹理“颜色”。

感谢帮助

编辑2:

我附上了我的整个代码，你能不能检查一下为什么我没有在屏幕上看到任何东西。

主.cpp:
#include <glad/glad.h>
#include <GLFW\glfw3.h> 
#include <iostream>
#include "shader.h"


#include "std_image.h"

using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        cout << "Failed to create GLFW window" <<endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        cout << "Failed to initialize GLAD" <<endl;
        return -1;
    }
    glViewport(0, 0, 800, 600);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    ///////////////////////////////////////////////////////////////////////////////////

    Shader ourShader("Shader.vs", "Shader.fs");

    Shader ourShader2("Shader.vs", "Shader2.fs");



    //glBindFramebuffer(GL_FRAMEBUFFER, 0);    //unbind framebuffer





    float vertices[] = {
        // positions          // colors           // texture coords
        0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f,   // top right
        0.5f, -0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        -0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   0.0f, 0.0f,   // bottom left
        -0.5f,  0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   0.0f, 1.0f    // top left 
    };
    unsigned int indices[] = {
        0, 1, 3, // first triangle
        1, 2, 3  // second triangle
    };

    float vertices2[] = {
        // positions          // colors           // texture coords
        0.75f,  0.75f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 1.0f,   // top right
        0.75f, 0.0f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        0.0f, 0.0f, 0.0f,  0.0f,1.0f, 0.0f,   0.0f, 0.0f,   // bottom left
        0.0f,  0.75f, 0.0f,  0.0f, 1.0f, 0.0f,   0.0f, 1.0f    // top left 
    };
    unsigned int indices2[] = {
        0, 1, 2, // first triangle
        0, 2, 3  // second triangle
    };


    unsigned int VBO[2],VAO[2],EBO[2];

    glGenVertexArrays(2, VAO);
    glGenBuffers(2, VBO);
    glGenBuffers(2, EBO);

    glBindVertexArray(VAO[0]);
    glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    glBindVertexArray(0);

    glBindVertexArray(VAO[1]);
    glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices2), indices2, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE);


    while (!glfwWindowShouldClose(window))
    {
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);


        ourShader.use();


        glBindVertexArray(VAO[0]);
        unsigned int FBO, color, depth;

        glGenFramebuffers(1, &FBO);
        glGenTextures(1, &color);


        glBindFramebuffer(GL_FRAMEBUFFER, FBO);
        glBindTexture(GL_TEXTURE_2D, color);
        glGenRenderbuffers(1, &depth);

        glTexImage2D(GL_TEXTURE_2D,
            0,
            GL_RGBA,
            800, 600,
            0,
            GL_RGBA,
            GL_UNSIGNED_BYTE,
            NULL);

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

        glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, color, 0);

        unsigned int decalTexLocation;
        decalTexLocation = glGetUniformLocation(ourShader.ID, "DecalTex");

        glUniform1i(decalTexLocation, 0);
        glActiveTexture(GL_TEXTURE0 + 0);
        glBindTexture(GL_TEXTURE_2D, color);


        GLenum DrawBuffers[2] = { GL_COLOR_ATTACHMENT0 };
        glDrawBuffers(1, &DrawBuffers[0]); // "1" is the size of DrawBuffers

        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
            return false;

        glViewport(0, 0, 800, 600); // Render on the whole framebuffer, complete from the lower left corner to the upper right
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);


        glBindFramebuffer(GL_FRAMEBUFFER, 0);


        ourShader2.use();

        glBindVertexArray(VAO[1]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);



        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    /*glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteBuffers(1, &EBO);*/

    glfwTerminate();
    return 0;
}

片段着色器1:
#version 330 core

out vec4 FragColor;

in vec3 ourColor;

void main()
{
  // vec4 dst = getCurrentColorAtOutputFragmentPosition();
   FragColor = vec4(ourColor, 1.0);
}

片段着色器2:
#version 330 core

out vec4 FragColor;

uniform sampler2D DecalTex;

in vec3 ourColor;

void main()
{
  vec2 coords = gl_TexCoord[0].xy;
  vec3 normalColor = texture2D(DecalTex, coords).rgb; //original color


   FragColor = vec4(normalColor.x,normalColor.y,normalColor.z, 1.0);
}

顶点着色器:
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;

out vec3 ourColor;
out vec2 TexCoord;

void main()
{
    gl_Position = vec4(aPos, 1.0);
    ourColor = aColor;
    TexCoord = aTexCoord;
}

编辑3:

在下面的代码中，我正在渲染 2 个矩形，其中一个是使用 FBO(帧缓冲区对象)的纹理，第二个是在屏幕上。

我能够在屏幕上呈现两者。

我写了 2 个片段着色器和 2 个顶点着色器。

一对片段和顶点着色器用于在纹理上渲染，另一对用于在屏幕上渲染。

我的主文件:
#include <glad/glad.h>
#include <GLFW\glfw3.h> 
#include <iostream>
#include "shader.h"


#include "std_image.h"

using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        cout << "Failed to create GLFW window" <<endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        cout << "Failed to initialize GLAD" <<endl;
        return -1;
    }
    glViewport(0, 0, 800, 600);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    ///////////////////////////////////////////////////////////////////////////////////

    Shader ourShader("Shader.vs", "Shader.fs");

    Shader ourShader2("Shader2.vs", "Shader2.fs");



    //glBindFramebuffer(GL_FRAMEBUFFER, 0);    //unbind framebuffer





    float vertices[] = {
        // positions          // colors           // texture coords
        0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f,   // top right
        0.5f, -0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        -0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   0.0f, 0.0f,   // bottom left
        -0.5f,  0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   0.0f, 1.0f    // top left 
    };
    unsigned int indices[] = {
        0, 1, 3, // first triangle
        1, 2, 3  // second triangle
    };

    float vertices2[] = {
        // positions          // colors           // texture coords
        1.0,  1.0, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 1.0f,   // top right
        1.0, 0.0f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        0.0f, 0.0f, 0.0f,  0.0f,1.0f, 0.0f,   0.0f, 0.0f,   // bottom left
        0.0f,  1.0, 0.0f,  0.0f, 1.0f, 0.0f,   0.0f, 1.0f    // top left 
    };
    unsigned int indices2[] = {
        0, 1, 2, // first triangle
        0, 2, 3  // second triangle
    };


    unsigned int VBO[2],VAO[2],EBO[2];

    glGenVertexArrays(2, VAO);
    glGenBuffers(2, VBO);
    glGenBuffers(2, EBO);

    glBindVertexArray(VAO[0]);
    glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    glBindVertexArray(0);

    glBindVertexArray(VAO[1]);
    glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices2), indices2, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    /*glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE)*/;

    unsigned int color;
    glGenTextures(1, &color);
    glBindTexture(GL_TEXTURE_2D, color);

    glTexImage2D(GL_TEXTURE_2D,
        0,
        GL_RGBA,
        800, 600,
        0,
        GL_RGBA,
        GL_UNSIGNED_BYTE,
        NULL);

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

    unsigned int FBO;
    glGenFramebuffers(1, &FBO);
    glBindFramebuffer(GL_FRAMEBUFFER, FBO);

    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);




    while (!glfwWindowShouldClose(window))
    {

        ourShader.use();

        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);


        glBindVertexArray(VAO[0]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);


        glBindFramebuffer(GL_FRAMEBUFFER, 0);


        ourShader2.use();

        int texturehandle = glGetUniformLocation(ourShader.ID, "DecalTex");
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, color);
        glUniform1i(texturehandle, 0);

        glBindVertexArray(VAO[1]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);




        glfwSwapBuffers(window);
        glfwPollEvents();
    }


    glfwTerminate();
    return 0;
}

Veretx 着色器 1:
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;

out vec3 ourColor;
out vec2 TexCoord;

void main()
{
    gl_Position = vec4(aPos, 1.0);
    ourColor = aColor;
    TexCoord = aTexCoord;
}

片段着色器 1
#version 330 core

out vec4 FragColor;

in vec3 ourColor;

void main()
{
  // vec4 dst = getCurrentColorAtOutputFragmentPosition();
   FragColor = vec4(ourColor, 1.0);
}

顶点着色器 2
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;

out vec3 ourColor;
out vec2 myUV;


void main()
{
    gl_Position = vec4(aPos, 1.0);
    ourColor = aColor;
    myUV = vec2(aPos.x,aPos.y);
}

片段着色器 2
#version 330 core

out vec4 FragColor;

uniform sampler2D DecalTex;

in vec3 ourColor;
in vec2 UV;

void main()
{
   vec2 outUV = vec2(0.26,0.26);
   vec4 myFragColor = texture2D(DecalTex,outUV);
   //vec4 myFragColor = texture2D(DecalTex,UV);
    //FragColor = vec4(ourColor,1.0);

    vec4 tempFragColor = vec4(ourColor, 1.0);

    //FragColor = myFragColor;

    FragColor = myFragColor + tempFragColor;

    //FragColor = (1.0,1.0,1.0,1.0);//tempFragColor;
}

这里的问题是，当我使用该行时:
vec4 myFragColor = texture2D(DecalTex,UV);

我无法在 myFragColor 中获得任何值，因此会发生正常渲染。

但如果我改为
vec2 outUV = vec2(0.26,0.26);
       vec4 myFragColor = texture2D(DecalTex,outUV);

我能够获得目标像素的值，因此根据我的需要进行渲染。

你能告诉我为什么我不能从:
vec4 myFragColor = texture2D(DecalTex,UV);

编辑 4

现在我可以访问我的目标像素，但只剩下 1 个问题:

第一个矩形坐标 (-0.5,-0.5) <-----> (0.5,0.5)

第二个矩形坐标 (0,0) <----> (1,1)

交叉区域 (0,0) <----> (0.5,0.5) --------> 这应该是黄色(红色 + 绿色)

但是区域 (0.26,0.26) <-------> (0.74,0.74) ------> 这是黄色的，很奇怪有什么原因..？

最新的片段着色器:
#version 330 core

out vec4 FragColor;

uniform sampler2D DecalTex;

in vec3 ourColor;
in vec2 myUV;

void main()
{


   vec4 myFragColor = texture2D(DecalTex,myUV);
    FragColor = vec4(ourColor,1.0);

    vec4 tempFragColor = vec4(ourColor, 1.0);


    FragColor = myFragColor + tempFragColor;

}

预期结果:

Expected Result

最佳答案

当你编译 Fragment Shader 2 时，你会收到这样的错误信息(取决于图形驱动程序)；

0(12) : error C7616: global variable gl_TexCoord is removed after version 140



这意味着您不能使用 gl_TexCoord结合 #version 330 core .

您已经定义了一个不同的 out顶点着色器中纹理坐标的变量。
out vec2 myUV;

定义对应的in片段着色器中的变量并使用它，而不是 gl_TexCoord :
#version 330 core

out vec4 FragColor;

uniform sampler2D DecalTex;

in vec3 ourColor;
in vec2 myUV;

void main()
{
    vec4 myFragColor = texture2D(DecalTex,myUV);
    FragColor = myFragColor;
}

对答案的扩展:

为了正确链接着色器程序并使其正常工作，不同的名称out变量必须与不同 in 的名称完美匹配变量。

这意味着这是命名 myUV 中纹理坐标的输出变量, 在顶点着色器中:
out vec2 myUV;

片段着色器中相应的输入变量必须命名为 myUV ， 也:
in vec2 myUV;

关于OpenGL 渲染到纹理，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46541334/

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